Wiadomości Chemiczne

Wiadomości Chemiczne, 2000, 54.

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  1. Density functional theory: foundations, kohn-sham realization, and concepts for chemistry
    Roman F. Nalewajski

  2. Quantum-chemical studies of parent nitrone [2+3] cycloaddition
    Andrzej Barański

  3. Internal solvation and proton transfer reactions in the gas phase for nitrogen compounds
    Ewa Daniela Raczyńska

  4. Metal ions as interfering factor in interactions of polyamines with fragments of nucleic acids
    Lechosław Łomozik, Anna Gąsowska

  5. Phosphorus nucleophilic reagents of the >P-O- type in the halophilic substitution reactions
    Janusz Rachoń

  6. Methods for the synthesis of polyethers from oxirane monomers
    Andrzej Stolarzewicz, Dorota Neugebauer

  7. Selenium compounds in the environment
    Krystyna Pyrzyńska

  8. Notatki chaotyczne XXVI. Rady spod dużego palca
    Ignacy Z. Siemion

  9. After celebrations of the 100th anniversary of the discovery of polonium and radium. Difficulties and misunderstandings related to the discovery of polonium
    Józef Hurwic

  10. Continuous and discrete solvent models in investigations of electronic structure
    Wojciech Bartkowiak, Józef Lipiński

  11. Proton transfer reactions between c-acids and organic bases in aprotic solvents
    Arnold Jarczewski

  12. Ecological misinformation
    Przemysław Mastalerz

  13. Raman spectroscopy applications in radiation chemistry and other research areas
    Halina Abramczyk

  14. Notatki chaotyczne XXVII. O zasadzie ograniczonego zaufania
    Ignacy Z. Siemion

  15. Aromaticity - A fundamental concept of modern organic chemistry. Part I
    Michał K. Cyrański, Tadeusz M. Krygowski

  16. Mathematical methods in chemistry: some applications of graph theory
    Janusz Nowakowski

  17. From supramolecular to molecular interactions
    Krystyna Brandt, Mariola Siwy, Dariusz Lach

  18. Investigation of silane gels by luminescence methods
    Ewa Miller

  19. Pharmacophore groups of the arylpiperazine ligands of serotonin 5-HT1A receptors
    Anna Wesołowska

  20. Dinitroamine (DNA), compounds with -N(NO2)2 group as potential components of energetic materials.
    Michał Syczewski, Iwona Cieślowska-Glińska

  21. Degradation of polychlorinated biphenyls
    Stanisław Gryglewicz

  22. Notatki chaotyczne XXVIII. O "niedoodkryciach"
    Ignacy Z. Siemion

  23. Quantitative criteria of aromaticity. Part II
    Michał K. Cyrański, Tadeusz M. Krygowski,

  24. Homogeneous hydrogenation of arenes
    Andrzej F. Borowski

  25. Carbonaceous deposits and their investigations by various techniques
    Jacek Góralski, Jacek Grams, Iwona Ludomirska, Tadeusz Paryjczak, Izabela Rzeźnicka

  26. In vitro selection of nucleic acids
    Barbara Nawrot

  27. Microcystins in water reservoirs
    Piotr Gajdek

  28. The multimedial textbook in chemistry teaching
    Hanna Gulińska, Andrzej Burewicz

  29. "Chemistry and art". Project in primary school
    Romuald Piosik

  30. Notatki chaotyczne XXIX. O definicji chemii i pewnej niedawnej decyzji Komitetu Badań Naukowych
    Ignacy Z. Siemion

  31. New directions in the guest of anti-cancer agents
    Elżbieta Mikiciuk-Olasik, Katarzyna Błaszczak-Świątkiewicz

  32. Advances in stereoselective sulfoxidation
    Jacek Skarżewski, Elżbieta Ostrycharz

  33. Selected applications of bornane-10,2-sultam (Oppolzer's sultam) in asymmetric organic synthesis.
    Aneta Szymańska, Ewa Wieczerzak i Leszek Łankiewicz

  34. Interfacial free energy and free energy of adsorption and micellization of surface active agents
    Bronisław Jańczuk, Wiesław Wójcik, Anna Zdziennicka

  35. Mesoporous molecular sieves, synthesis and properties
    Stanisław Kowalak, Krystian Stawiński

  36. Model quantum-mechanical calculations in chemistry
    Jens Abildgaard, Poul Erik Hansen

  37. Thermodynamics of saturated solutions and solubility
    Henryk Buchowski

  38. Notatki chaotyczne XXX. O pamięci i jej perfidnym wrogu: chorobie Alzheimera
    Ignacy Z. Siemion

  39. Profesor Maciej Wiewiórowski the co-founder of modern chemical research in poland
    Wiesław Zygmunt Antkowiak

  40. Influence of the partial order of molecular orientation on the high resolution NMR spectra
    Andrzej Ejchart, Adam Gryff-Keller

  41. Hydrogen bonded complexes of urea
    Jerzy Polaczek, Wojciech Domanowski

  42. The role of van der Waals complexes in the thermal electron capture processes in the gas phase
    Iwona Szamrej

  43. Synthesis of organic peroxy compounds
    Stefan Baj, Małgorzata Dawid

  44. The alkali metals of negative oxidation number
    Andrzej Misiołek , Violetta Łysiak, Krystyna Jarzembek

  45. Biologically active bisphosphonates. Structure, synthesis, properties and action
    Ewa Bałczewska, Piotr Bałczewski

  46. Oxygenated derivatives of cholesterol. occurrence, biological activites, methods of analysis
    Danuta Bodzek, Beata Janoszka, Tomasz Wielkoszyński

  47. Notatki chaotyczne. XXXI. Chemia i mineralogia w twórczości Juliusza Słowackiego
    Ignacy Z. Siemion

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DENSITY FUNCTIONAL THEORY: FOUNDATIONS, KOHN-SHAM REALIZATION, AND CONCEPTS FOR CHEMISTRY

Roman F. Nalewajski

Zakład Chemii Teoretycznej im. K. Gumińskiego, Uniwersytet Jagielloński, ul. R. Ingardena 3, 30-060 Kraków


Thirty five years after Hohenberg and Kohn discovered in 1964 that the electronic density r(r) can be used as the basic quantity in the rigorous formulation od the theory of electronic structure of matter, the modern density functional theory (DFT) has developed into an already mature discipline, which offers both attractive computational tools for applications in physics, chemistry and molecular biology, and a new conceptual framework for predicting and rationalizing preferences in chemical processes. Computational advances, originating from the other, almost as old historical development by Kohn and Sham (KS) in 1965, have demonstrated that the accuracy of the modern DFT software in the mostly ground-state applications has reached the level of the 3chemical accuracy 1, comparable to that offered by the sophisticated and prohibitively expensive traditional quantum chemistry methods, which explicitly determine the correlated N-electron wavefunction of a molecular system. The importance of these two branches of computational quantum chemical methods in modern chemistry has been recognized by the 1998 Nobel Prize for Chemistry [W. Kohn (density theory) and J.A. Pople (wavefunction theory)].

The Hohenberg-Kohn/Kohn-Sham theories have been generalized to thermal ensembles, multicomponent systems, spin and orbital paramagnetism, and superconductivity. The recent developments also cover the relativistic and excited-states theories, time dependent systems and the DFT for sybsystems, the latter being of paramount importance for the theory of chemical reactivity. The applications of DFT range from the ground-state properties of solids, through calculations on molecular systems of chemical/biological importance to high temperature plasmas. A combinations of DFT with molecular dynamics has prompted a spectacular progress in calculations on the ion dynamics in solids and the equilibrium structures of large molecular clusters with up to ~102 atoms. Very recently, progress has also been made in developing approaches behaving linearly with the number of electrons, which show promise of handling truly large systems consisting of ~103 atoms.

This spectacular success of the computational DFT is matched by its conceptual significance in chemistry. DFT gave a new impetus for developing novel, more reliable reactivity criteria and offered a new thermodynamical outlook on elementary chemical processes. It has soon been discovered that DFT provides the rigorous basis for defining many classical chemical concepts, which had originally been introduced on intuitive/phenomenological grounds, e.g., the electronegativity and hardness/softness characteristics of the electronic distribution in molecules. It resulted in more rigorous theoretical justifications of important rules of chemistry, soon to be followed by general variational principles for chemistry, which both elegantly united many facets of the electronic structure/chemical reactivity facts, and allowed for more accurate predictions of behaviour of chemical species.

Despite this success of DFT, the knowledge of its basic theorems and generalizations is not widespread among chemists, to the best knowledge of the Author. Even in the university quantum chemistry course this subject is rarely mentioned, with the methodological core usually covering exclusively the traditional Hartree-Fock (HF) molecular orbital theory and its configuration interaction (CI) extensions. Little is known, for example, about the conceptual advantages of the Kohn-Sham orbitals over their HF counterparts, and the physical interpretation of the former. This review article, written in response to a kind invitation of this Journal Editor, attempts to fill this gap. This monographical survey covers the Hohenberg-Kohn theorems and their ensemble extensions due to Mermin, elements of the Kohn-Sham and Kohn-Sham-Mermin theories, and rudiments on the crucial density functional for the exchange-correlation energy.

The discussion of the KS approach includes the KS equations for the optimum canonical orbitals and an analysis of the physical significance of the KS molecular orbitals, corresponding to a fictitious system of non-interacting electrons. The general form of the crucial functional for the exchange-correlation energy Exc[r] is summarized and the density scaling argument for its Local Density Approximation and the first nonlocal (density gradient) correction is presented. A general form of Exc[r] in terms of the exchange-correlation hole is introduced and specific examples of the non-local exchange and correlation functionals are given. Finally, some advantages of the related orbital dependent functionals Exc[{fi[r]}] used in the Optimized Effective Potential method are briefly mentioned.

An emphasis is also placed upon selected concepts for chemistry. In particular characteristics of the electronic "gas" in open molecular systems, covering the chemical potential (negative electronegativity), Fukui function, and the absolute measures of the chemical hardness (softness), are discussed in a more detail, including their behaviour in the zero temperature limit. It is argued that DFT facilitates a thermodynamical-like description of the polarization and charge-transfer phenomena in molecular systems, e.g., those accompanying interaction between reactants, adsorbate and substrate in heterogeneous catalysis, etc.


Wiadomości Chemiczne, 2000, 54, 1.
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QUANTUM-CHEMICAL STUDY OF PARENT NITRONE [2+3] CYCLOADDITION

Andrzej Barański

Instytut Chemii i Technologii Organicznej Politechniki Krakowskiej, ul. Warszawska 24, 31-155 Kraków


The present paper is an attempt to systematize the literature data concerning quantochemical calculations of transition states for [2+3] cycloaddition of parent nitrone to alkenes, thioformaldehyde, isocyanates, acetylene and molecular oxygen.

In the case of reaction with ethylene the attained transition states are nearly symmetrical. Individual methods differ in their estimation of of the resultant bonds is more advanced. For reaction in question there is a lack of experimental parameters of activation. It is generally know, however, that activation energy for [2+3] cycloaddition of typical nitrones to alkenes are in range 13-18 kcal/mol. In the case of HF calculations the activation energy is clearly overestimated. Better results are attained by taking into account the electron correlation, in which the most accurate results are obtained using the advanced method MP4SDQ. The MP2 method considerably loweres the values of activation energy, which rectifies methods MP3 and MP4. Differing results are also obtained using density functional theory (DFT). As expected the most unreliable results were obtained using VWN functional. Only calculations close to the NLDA approximation allowed the attainment of reliable results. If the MP4 method is taken as the reference method, then the closed to this as regards activation energy values is the functional B3LYP. A much lesser influence on the description of the reaction under discussion is the type of basis set. The results of the HF calculations (without electron correlation) are equaly unreliable in the minimal STO-3G base, as well as in the more advanced 6-311G** base. So for a reasonably reliable description of the reaction of [2+3] cycloaddition between nitrones and alkenes, it seems imperative to apply the methods which take into account the effects of electron correlation.

A similar relationship of activation energy regarding the type of calculation method applied can be observed in the case of reaction of parent nitrone with thioformaldehyde, isocyanates, acetylene and molecular oxygen.


Wiadomości Chemiczne, 2000, 54, 53.
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INTERNAL SOLVATION AND PROTON TRANSFER REACTIONS IN THE AS PHASE FOR NITROGEN COMPOUNDS

Ewa Daniela Raczyńska

Katedra Chemii Ogólnej, Szkoła Główna Gospodarstwa Wiejskiego, ul. Rakowiecka 26/30, 02-528 Warszawa


Intramolecular hydrogen bonding which can be formed in the neutral or ionic forms of polyfunctional compounds strongly influences the simple proton-transfer reactions and tautomeric equilibria in the gas phase.

This effect, called internal solvation increases the proton affinities of nitrogen ligands, such as proton sponges with a rigid structure (Table 1), and diamines, amidinamines, bipyridines and amidinazines with a flexible conformation (Table 2) by 20-100 kJ/mol in comparison to monofunctional or model compounds [7-16, 19-21, 25, 27, 55]. In consequence diamines and amidinamines belong to superbases (PA>1000 kJ/mol) [14, 55, 63, 67].

In aqueous solutions, only proton sponges are strong bases. Due to strong steric effects, water molecules cannot open the ionic N···H-N+ bridge in the proton sponges [25, 51-55]. Bidentate nitrogen ligands with a flexible conformation behave in solution similarly as monofunctional derivatives [56]. External solvation by water molecules eliminates the N···H-N+ bridge, changes conformation of the monocation (from cyclic to linear), reduces polarizability of the chain, and thus decreases the basicity.

For tautomerizing azoles, the internal solvation changes the pKT values by more than 2 pKT units in comparison to derivatives without this interaction [24]. Application of the Taft and Topsom equation (7) [43] to series of 4(5)-substituted imidazoles indicates that the internal solvation in the gas phase has similar influence on the transmission of substituent effects as the external solvation in water (Table 3).


Wiadomości Chemiczne, 200, 54, 67.
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METAL IONS AS INTERFERING FACTOR IN INTERACTIONS OF POLYAMINES WITH FRAGMENTS OF NUCLEIC ACIDS

Lechosław Łomozik, Anna Gąsowska

Wydział Chemii Uniwersytetu im. Adama Mickiewicza, ul. Grunwaldzka 6, 60-780 Poznań


Structurally simple aliphatic polyamines: putrescine (Put), spermidine (Spd) and spermine (Spm) occur in the cells of living organisms (human, animals, plants and bacteria) in relatively high concentrations. These compounds participate in many living processes [1-4 and references therein]. The mechanism of their biosynthesis is well recognised [5,6], Scheme 1. High basicity of polyamines implies that in the physiological conditions they appear in the protonated form and thus can interact with the negative fragments of other biomolecules. According to the polyelectrolytic theory of Manning [31-38], structural changes of particular molecules in interactions with the other components of the system depend mainly on the charge of the reagents, however, this approach does not explain a high specificity of certain reactions. It has been recently suggested that apart from the charge, also the polycation structure seems to play an important role [39, 40]. Computer analysis of the potentiometric titration data allowed a determination of the stability constants of molecular complexes formed by polyamines and fragments of the nucleic acids. Analysis of the titration and the spectral data indicates that at least two active centers are needed to obtain a relatively stable adduct [62]. The thesis saying that the main sites of interactions are the protonated amine groups from PA and the negative or high electron density fragments of nucleosides or nucleotides (ion-dipole or ion-ion interactions) has been confirmed by the pH ranges of the molecular complexes occurrence, Fig. 2.

In nucleosides and nucleotides the main sites of metallation are the donor endocyclic N(3) atoms from the pyrimidine ring and N(1) or N(7) atoms from the purine ring. Phosphate groups of nucleotides are also effective centers of reaction. Polyamines change the character of the coordination dichotomy (mixture of isomers with the N(1) or N(7) coordination) observed in the metal-nucleoside (or nucleotide) systems. In general, with increasing length of the polyamine, the tendency to formation of heteroligand mixed complexes decreases and, interestingly, this tendency is exactly the opposite to that of formation of molecular complexes Nuc/PA. Already small changes in the polyamine length significantly affect their complex formation properties and reactions with metal ions or molecules in living cells [76, 77]. This explains the differences in the properties of biogenic amines and their biologically inactive homologues. In the ternary systems Cu/Nuc/Spm and Cu/NMP/Spm some interesting differences were observed in the coordination mode of the complexes. In the complex Cu(Nuc)(Spm) the metal ion was found to coordinate four nitrogen atoms from the polyamine in the equatorial plane and the N(3) or N(7) atom at the axial position (coordination structure of the square pyramid). In the system with the nucleotide, Cu(II) binds the phosphate group, while the polyamine is involved in non-covalent interaction with the donor nitrogen atoms from the purine or pyrimidine base [67, 78] and forms an adduct with intermolecular non-covalent complex-ligand interactions, Fig. 4. In the systems with nucleosides, copper ions inhibit the interactions of adenosine or cytidine with polyamines. On the other hand, spermine involved in the non-covalent interaction with a nucleotide base blocks the potential metallation sites of AMP or CMP, changing essentially the character of coordination.

Considering the role of the complexation processes in the above model systems, it should be added that formation of PA complexes with metal ions and fragments of nucleic acids is a factor ensuring homeostasis of polyamines in living cells. Reduction of the effect of diamine oxidase on the amines involved in the complexation processes increases their lifetime in living organisms [52].


Wiadomości Chemiczne, 2000, 54, 87.
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PHOSPHORUS NUCLEOPHILIC REAGENTS OF THE >P-O- TYPE IN THE HALOPHILIC SUBSTITUTION REACTIONS

Janusz Rachoń

Katedra Chemii Organicznej, Wydział Chemiczny Politechniki Gdańskiej, ul. Narutowicza 11/12, 80-952 Gdańsk


One of the oldest pathways for the formation of carbon - phosphorus bond is the Michaelis - Becker reaction [14 - 18]. The mechanism of this reaction is assumed to be SN2 process involving nucleophiles of the >P-O- type and C-halogen electrophiles. On the other hand dialkyl phosphite anions are known to participate in aromatic [20 - 22] as well as aliphatic [ 23 - 27] SRN1 processes. In the literature one can find some examples of an unusual course of the Michaelis-Becker reaction. The reaction between bromotriphenylmethane and sodium diethyl phosphite was claimed to be a free radical process [28, 29]. It was shown recently [41 , 42] that the anions of the >P-O- type as well as >P-S- undergo reaction with a-bromocarboxylates and - phosphonates yielding debrominated products.

The anions of the >P-O- type are of special interest; they are nucleophilic ambident reagents, strong bases, and are suggested to be single electron donors [20 - 27]. On the other hand the compounds of the >P(O)H structure can act as proton or hydrogen [12, 13] sources; depending on the structure and reaction conditions.

The results of current investigations show that in the case of the carbon bromine bond, also bromine can be a target for nucleophilic attack by the phosphorus reagent of the >P-O- as well as >P-S- types with the release of the carbanion as nucleofuge. It was demonstrated [58] that according to the reduction potential of p-substituted benzyl bromides and the solvent used in the reaction of these starting materials and the nucleophilic reagent of the >P-O- type the formation of the P-C bond, debromination and/or dimerization occur.

The influence of light on the products distribution [ 56, 58] as well as the results of the free radical trap experiments [57] have resulted in a reasonable picture of the mechanism of the reaction between p-substituted benzyl bromides and >P-O- nucleophiles outlined in Scheme 16. The results of current research strongly speak for the X-philic substitution as the principal process in the reaction between bromoalkanes possessing the electron - withdrawing groups and >P-O- nucleophiles ( Scheme 16, eq a ). This nucleophilic attack of the >P-O- anion on the bromine atom results in formation of carbanion , which, depending on the redox potentials, can participate in the proton ( Scheme 16, eq b ) and / or electron transfer ( Scheme 16, eq c ) processes producing debrominated products and / or dimers . The anions of the >P-O- type can act rather as a carbon radical trap and not as a single electron donor.


Wiadomości Chemiczne, 2000, 54, 105.
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METHODS FOR THE SYNTHESIS OF POLYETHERS FROM OXIRANE MONOMERS

Andrzej Stolarzewicz, Dorota Neugebauer

Centrum Chemii Polimerów Polskiej Akademii Nauk im. M. Curie-Skłodowskiej 34, 41-819 Zabrze


Methods of the oxiranes polymerization and the influence of the process conditions on the structure and properties of polyethers obtained are discussed. There are presented new methods for the synthesis of polyethers with hydroxyl end groups.

In one of them double metal cyanide (DMC) complexes are used for the polymerization of propylene oxide and other oxiranes [69-75]. The high activity is shown by a system containing Zn3(Co(CN) 6) 2 with the addition of zinc chloride, dimethoxyethane and water. Diols and triols with Mn up to 10 000, and with a very low amount of the monol fraction are obtained from propylene oxide. Potassium hydride and a crown ether are applied as the anionic initiator system in another method [81-86]. Polymers of propylene oxide are formed in this case with Mn within the range between 6 000 and 12 000. They are mainly diols and they also contain the monol fraction. The chain transfer reaction to the monomer does not occur or its rate is strongly limited in the polymerization of some other oxiranes by potassium hydride. It allows to obtain the molecular weight of polyethers higher than that in the presence of the anionic initiators known so far. The Mn = 39 000 is found for example for poly(butylene oxide).


Wiadomości Chemiczne, 2000, 54, 127.
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SELENIUM COMPOUNDS IN THE ENVIRONMENT

Krystyna Pyrzyńska

Wydział Chemii, Uniwersytet Warszawski, ul. Pasteura 1, 02-093 Warszawa


From the time selenium was discovered in 1817 by Berzelius, until the recognition in the late 1950s of its toxicity and, subsequently, its essentiality for humans, a large number of its properties have been elucidated. Apart from natural sources (mainly metal-sulfur minerals) selenium compounds can widely spread throughout the environment as a result of combustion of coals and its uses in the glass and electronic industries.

Natural waters, soils and air are the most commonly studies environmental media. Selenium naturally exists in several oxidation states and in inorganic and organic forms. The inorganic selenium species most frequently found in waters and soils are selenite (SeO32-) and selenate (SeO42-).Selenites have high affinity for metal hydroxide and are adsorbed onto insoluble compounds. Under acidic conditions they are rapidly reduced to elemental red selenium. Alkaline and oxidising conditions favour the formation and stabilisation of selenate [5-10]. Several organoselenium compounds have been identified with direct Se-C bound including methylated species, selenoamino acids, selenoproteins and their derivatives. Inorganic selenium compounds can be transformed into volatile species such as dimethylselenide - (CH3) 2Se and dimethyldiselenide - (CH3) 2Se2 through microbial action [11-13]. These methylation reactions are considered to be detoxification steps, because methylated compounds are less toxic [14].

Selenium has been recognised as an essential nutrient for humans based on its presence in the enzyme glutathione peroxidase, which affords cell protection against oxidative damage [17]. Its compounds also catalyse the reactions of intermediate metabolism and inhibit the toxic effects of heavy metals, such as lead, cadmium and mercury. The recommended daily dietary allowances of selenium for adult humans is in the range of 50 - 70 (g [24]. On the other hand, there is also some evidence that in higher concentration toxicity effect of this element can occur. The maximum recommended selenium concentration in drinking water is 10 mg/dm3 [4].

As physiological effect of selenium have been realised in recent years, there has been increasing interest in the trace determination of this metal. The analytical methods for selenium determination in different matrices have been recently reviewed [3,25-27].

However, selenium reactivity and bioavailability depend not only on its total amount. Additional knowledge of the chemical forms and oxidation states in which this element exist is needed. Compared with the extensive investigations on total selenium or selenite and selenate determination, very little work has been done with organic selenium compounds, especially in foods [43-46]. Selenomethionine (probably the major form of selenium in cereals) is retained in tissue proteins to a much greater extent. Intake of other forms of selenium, such as selenite or selenocysteine will be excreted in the urine if it occurs in the excess [14,46].


Wiadomości Chemiczne, 2000, 54, 139.
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NOTATKI CHAOTYCZNE XXVI. RADY SPOD DUŻEGO PALCA

Ignacy Z. Siemion

Wydział Chemii Uniwersytetu Wrocławskiego, ul. F.Joliot-Curie 14, 50-383 Wrocław


Wiadomości Chemiczne, 2000, 54, 151.
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AFTER CELEBRATIONS OF THE 100th ANNIVERSARY OF THE DISCOVERY OF POLONIUM AND RADIUM. DIFFICULTIES AND MISUNDERSTANDINGS RELATED TO THE DISCOVERY OF POLONIUM

Józef Hurwic

Laboratoir de Dielectrochimie, Universite de Provence, 3, pl. Victor-Hugo, 13331 Marseille CEDEX 03, France


The amount of polonium sulfide obtained in 1898 by M. and P. Curie was so insignificant that a chemical or even spectral identification of the new element was imposible. The Curies were guided in their work by the chemical resemblance of polonium to bismuth; W. Marckwald demonstrated the similarity between polonium and tellurium. There were doubts if polonium is a chemical element - in contrast with the uranium, thorium, actinium and even radium its radioactivity felled very fast. An opinion was even expressed that in reality the so-called "polonium" is bismuth "activated" by radium present in pitchblende. It was not until 1910 that for the first time the spectral lines of polonium were inedtified


Wiadomości Chemiczne, 2000, 54, 177.
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CONTINUOUS AND DISCRETE SOLVENT MODELS IN INVESTIGATIONS OF ELECTRONIC STRUCTURE

Wojciech Bartkowiak, Józef Lipiński

Instytut Chemii Fizycznej i Teoretycznej, Politechnika Wrocławska,
Wyb. Wyspiańskiego 27, 50-370 Wrocław


Solvent effects play a very important role in chemistry since most chemical reactions and biological processes take place in solution. Accurately representing the influence of solvent upon molecules in solution is an important and long-standing goal of theoretical chemistry. A particular important aspect of solvation is the electrostatic interaction of solute system with its surroundings. The aim of this work was to present and compare various theoretical treatments of solvent effects, based on continuous models ( Born-Onsager-Kirkwood method, virtual charge method, generalized Born method, polarizable continuum model and conductor-like screening model) and discrete representation of solvent molecules (Monte Carlo and molecular dynamics methods, free energy perturbation method, reference interaction site method and Langevin dipoles model).


Wiadomości Chemiczne, 2000, 54, 183.
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PROTON TRANSFER REACTIONS BETWEEN C-ACIDS AND ORGANIC BASES IN APROTIC SOLVENTS

Arnold Jarczewski

Zakład Chemii Ogólnej, Wydział Chemii, Uniwersytet im.A.Mickiewicza,
Grunwaldzka 6, 60-780 Poznań


The proton transfer reactions in solutions seem to be simple, yet a number of consecutive steps can be distinguished [1]. The useful tool in determining the mechanisms of these reactions was, and still is the primary deuterium kinetic isotope effect [2-18]. Therefore the factors influencing the rate constants and then KIE of these reactions as: steric hindrance of reactants, polarity of solvents and symmetry of transition state were widely discussed 18-63]. The commonly acepted view on the deuterium kinetic isotope effects is that they are large when bulky substituents are crowded around the reaction site [19-21], and also the reactions are carried out in low polarity solvent [25-28]. However, there was found that even in polar aprotic solvents as acetonitrile large KIE values take place [26-28, 40, 41]. The KIE values are not very sensitive on the steric hindrance [18,56], showing in some extreme cases reduced KIE values [18, 53, 56], what is incompatible with previous papers [22, 23, 34-37, 40-52]. Likewise some other effects as "scrambling effect" simulating very large KIE are considered [29-38].

The products of proton transfer reactions between C-acids and strong organic bases in polar aprotic solvents in contrary to previous findings [22, 25] appeared to be highly dissociated into free ions [41, 67]. The reason and consequences of erroneous fulfillment of Benesi-Hildebrand [64] equation are discussed. It was essential to carry out the kinetic study of the proton transfer reactions, in particular those of low equilibrium constants in a BH+/B buffer. Then the association effect should be considered [68]. Also a number of homoconjugation constants for selected organic bases [68, 69, 69a, 69b] and equilibrium acidities of some C-acids [117] in acetonitrile solvent are given.

The study of proton transfer reactions in mixed H2O-Me2SO solution prevented the homoconjugation effects and gave the thermodynamic and kinetic acidity, what enabled to evaluate the intrinsic barriers or intrinsic reactivity [70-78]. To assess the aci-nitro behavior of C-acids the protonation reaction of 4-nitrophenylnitromethane carbanion at different pH values were performed [71, 72, 80-91].

The influence of residual water which cannot be removed completely from the reaction systems of C-acids and strong organic bases in aprotic solvent was a subject of interest for many years [29-32, 37, 40, 98]. After careful examination it appeared that the traces of water in reaction medium, in aprotic solvents, caused a marked decrease of reaction rate instead of its acceleration [97]. It was clamed that the reactivity of ion pairs is negligible compared to free ions [99-101]. However, in some cases the reactions are going via ion pair reagents with distinct differentiation of reactivity between loose and tight ion pairs [99, 107, 108]. Using literature values of the fractionation of cesium n-propoxide for ions and ion pairs [110, 111], 2.5 times larger reactivity has been found for ion pairs than free ions in proton abstraction from 1-(4-nitrophenyl)-1-nitroethane [109]. The recent progress in the study of proton transfer reactions indicates new aspects in understanding the mechanism and theory of these processes.


Wiadomości Chemiczne, 2000, 54, 203.
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ECOLOGICAL MISINFORMATION

Przemysław Mastalerz

ul. Gliniana 23/17, 50-525 Wrocław


The popular perception of environmental threats is marred by severe misconceptions originating from false information relentlessly propagated by dishonest ecowarriors in collusion with sensation-seeking mass media. The purpose of this article is to denounce the most blatant lies and to show their ideological, tactical and political backgrounds. Discussed are also the potentially harmful consequences of present environmental policies for the well-being of humanity.

The article opens with a presentation of some seemingly trifle but characteristic ecological lies and then proceeds with a discussion of misinformation concerning the most serious ecological problems includin industrial pollutants, combustion of municipal solid waste, global climate change, ionizing radiation hazards and the present frenzy concerning the electromagnetic smog. Chemical pollutants discussed here include heavy metals, pesticides, nitrates and various chlorinated organic compounds with special consideration of dioxin and other persistent organochlorine. A separate chapter deals with cancerogenic chemical products.

The critique of common misconceptions is based on thorough evaluation of frequently conflicting scientific evidence but intricate details of scientific discissions are avoided for a more distinct exposure of basic tenets. It is shown that several difficult environmental problems are best resolved by application of basic knowledge and common sense.

The chemical and radiation threats are presented together with a discussion of the linear hypothesis which states that there are no safe doses of harmful agents. This hypothesis is een as the most important cause of the now prevailing fears of chemistry and of ionizing radiation.

Numerous verbatim quotations from articles in daily newspapers and weekly magazines demonstrate that incompetent and frequently histerical reporting is at the backround of many environmental scares which are now haunting the mankind


Wiadomości Chemiczne, 2000, 54, 227.
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RAMAN SPECTROSCOPY APPLICATIONS IN RADIATION CHEMISTRY AND OTHER RESEARCH AREAS

Halina Abramczyk

Instytut Techniki Radiacyjnej, politechnika Łódzka, ul. Wróblewskiego 15, 93-590 Łódź


Raman spectroscopy has evolved into one of thje most powerfull tools for fundamental investigations and practical characterizations of gases, liquids and solids. The technique can unravel almost any kind of low-frequency excitations in almost any type of solids. Compared with other techniques of analitical chemistry, it has the advantages of non-destructive in situ applications, high spectral and spacial resolution and possibility of using microscopic surface topographies. In this paper some examples of Raman applications in radiation chemistry, characterization of advanced materials, compounds of pharmaceutical interest and applications to the identification of pigments on paintings and manuscripts are given.


Wiadomości Chemiczne, 2000, 54, 325.
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NOTATKI CHAOTYCZNE XXVII. O ZASADZIE OGRANICZONEGO ZAUFANIA

Ignacy Z. Siemion

Wydział Chemii Uniwersytetu Wrocławskiego, ul. F.Joliot-Curie 14, 50-383 Wrocław


Wiadomości Chemiczne, 2000, 54, 345.
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AROMATICITY - A FUNDAMENTAL CONCEPT OF MODERN ORGANIC CHEMISTRY. Part I

Michał K. Cyrański, Tadeusz M. Krygowski

Uniwersytet Warszawski, Wydział Chemii, ul. L. Pasteura 1, 02-093 Warszawa


Aromaticity is one of the most often used terms in chemistry (Table 1). It is not a single property, but a multidimensional phenomenon which can be defined only by convention. Various typical characteristics of aromaticity not always occur to be equivalent. As a ground for these definitions it is usually accepted that aromatic compounds are those cyclic p-electron systems which exhibit the following properties:

(i) They are more stable than the non-cyclic analogues;

(ii) Their bond lengths are intermediate between the typical double and single bonds;

(iii) They exhibit special magnetic properties: in the external field the p-electron ring current is induced.

Sometimes an additional criterion is postulated: the aromatic systems react in the way to retain their p-electron structure. Most often it means that the substitution is preffered over the addition reaction. While the first three criteria may be transformed into quantitative parameters called aromaticity indices, reactivity can be used only in a qualitative way.


Wiadomości Chemiczne, 2000, 54, 357.
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MATHEMATICAL METHODS IN CHEMISTRY: SOME APPLICATIONS OF GRAPH THEORY

Janusz Nowakowski

Zakład Chemii Teoretycznej, Instytut Chemii Uniwersytetu Śląskiego, ul. Szkolna 9, 40-006 Katowice


The mathematization of chemistry has a long history. In 1874 Brown, one of the great pioneers of chemical structure theory, prophesied that " ... chemistry will become a branch of applied mathematics ... and enable to justify results obtained by experiment and predict entirely novel discoveries". This prophesy was soon to be fulfilled. In 1875 the British mathematician Cayley enumerated both the isomers of alkanes and alkyl radicals based on the graph theory. He realized that chemical graphs could be used to present molecules because of the isomorphism that exists between such graphs and molecular structures [2]. This relation plays an important role in application of the graph theory in modern chemistry [3].

In the article a brief description of the results in the field of enumeration and generation of isomers is given. The connections between chemical terms and quantities of mathematical graph theory are shown [Tab. 2]. Illustrative examples [ Tab. 1, Fig. 2-6], are chosen and mathematical principles of the methods are presented [18-20]. Recent papers on enumeration of isomers are compiled [29-49, 51, 54, 55, 59].

The topological matrix in Hückel molecular orbital method is isomorphic with the adjacency matrix of molecular graph. Isospectral graphs within the Hückel molecular orbital method correspond to conjugated molecules having the same set of orbital energies and related physical and chemical properties [3, 60]. Therefore the generation of isospectral graphs may be used to find similar chemical compounds. The methods of such generation based on some quantumchemical and informative characteristics are described [Fig. 8-9, Tab. 3-4, 61, 62, 64].

Computers enable today the practical use of the mathematical methods mentioned in the article. Even the personal computers are useful in the topic. Some calculations can be done on-line by Internet or with the use of commercial computer programs [27, 29, 52, 63, 64].


Wiadomości Chemiczne, 2000, 54, 371.
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FROM SUPRAMOLECULAR TO MOLECULAR INTERACTIONS

Krystyna Brandt, Mariola Siwy, Dariusz Lach

Centrum Chemii Polimerów PAN, ul. M. Curie-Skłodowskiej 34, 41-800 Zabrze


The review is focused on the problems of supramolecular assistance to molecular synthesis which means the employment of supramolecular interactions to control the chemical synthesis, i.e. to guide the regio- and/or stereoselective formation of covalent and/or mechanic bonds. Such an approach results from the tendency to mimic processes occurring in natural biological systems.

The special attention is focused on the recent achievements in this field, i.e. on the design of so-called intelligent substrates, which contain in their structure the requisite stereoelectronic information needed to self-assemble spontaneously into a supramolecular intermediate, which converts further into a desired final product after the formation of one or more covalent bonds. Among the unusual structures obtained using this synthetic paradigm, mechanically interlocked molecular compounds, i.e. rotaxanes, catenanes and their supramolecular precursors: psedorotaxanes, are described in more detail, as they display features of bistable chemical switches, and therefore evolve currently a great scientific interest due to their prospective applications in nanotechnologies.

Several examples have been given of supramolecular assistance to other complex chemical syntheses, in particular of organic compounds, organo(cyclophosphazenes) and oligonucleotides, enabling to perform them quickly and selectively from polyfunctional reagents, without the necessity to use any protecting groups.

It has been emphasized that supramolecular interactions play a special role in guiding so-called self-replication processes of the molecules containing in their structure both reactive groups, able to undergo co-condensation, and complementary to those contained in the substrates supramolecular synthons (motifs), capable to form appropriately oriented ternary complexes with these substrates, in which the functional groups are in favourable position to interact towards the desired product.

An influence of spontaneous self-assembly of the substrates, preceding their linking via covalent bond(s), on regio- and stereochemistry of the occurring processes has been discussed, with the special attention being paid to the role of so-called templates (previously named matrices), determining the orientation of the substrates due to the stabilization of particular transition states. Several types of templates have been discussed: complementary hydrogen bonding, metal cations (alkali metal, transition metal), p-donor-p-acceptor interactions and various combinations of the above mentioned; the examples of the respective template-driven syntheses have been quoted.

The reactions of functional macrocyclic ligands, assisted by supramolecular interactions with the nucleophilic ion-paired co-reagents, have been only briefly mentioned and limited to the examples of the exchange reactions of benzo-crowns with substituents in aromatic rings, and of chlorocyclophosphazene-crowns, because these problems have been recently presented by us in detail in the review article [43] and book [59].


Wiadomości Chemiczne, 2000, 54, 389.
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INVESTIGATION OF SILANE GELS BY LUMINESCENCE METHODS

EWA MILLER

Zespół Chemii Fizycznej i Koloidów, Instytut Podstaw Chemii Żywności, Wydział Chemii Spożywczej i Biotechnologii, Politechnika Łódzka, Ul. B. Stefanowskiego 4/10, 90-924 Łódź


Recently, optical sensors (optodes) are very often applied in biomedical sciences and biotechnology in analytical methods which require high sensitivity, selectivity and accuracy. The methods consist in the transmission of analyzed radiation by means of an optical fibre from the source to the sensor, and then of the response from the sensor to the detector also in the form of a light signal at a changed wavelength. A chromophore indicator sensitive to changes in physicochemical properties of an analyzed substance that take place in the reaction system is immobilized on the surface of an optical waveguide.

Advantages of the optodes include, among other things, no need to use a reference signal, a very small size and weight, elasticity, a possibility of using distant measurements (up to 1 km) a simple sensor construction and low price.

These sensors can be used in the analysis of samples in both liquid and gas phase [1-4]. This is why they found application in the environmental protection to analyze groundwater and flue gases [5], in toxicology [6] and to test product quality in the food industry [7]. If an enzyme which catalyzes an appropriate chemical reaction or a co-immobilized enzyme with a sensor transforming changes in the concentration of a substance being formed or decayed as a result of the enzymatic reaction, is immobilized on the fibre surface, then also biologically important compounds such as glucose [8], fructose [9], urea [10], lactate [11], amino acids [12], as well as pH [57, 58] can be determined.

In the latest studies on the formation of optical materials, especially an organic chromophore immobilizer, researchers often use silane gel which is obtained by the sol-gel technique. In comparison to a high-temperature synthesis of silica glass, the advantage of preparing silane matrices by gelation is that the process requires very mild conditions. This is why an organic compound, e.g. a luminescence probe, introduced to the input sol is not degraded during the gelation process.

This paper describes the process of silane gelation in the classical approach according to Flory-Stockmayer's theory [16] and then using the percolation theory [Table, 17]. Further on, methods of silane gel formation based on the latest studies are presented [22-26]. Recent studies on the gelation process based on the excimer spectrum of a classical pyrene probe are discussed [31-34]. Results of the studies, on the basis of which changes were observed in viscosity and polarity of the fluorophore microenvironment during gelation, are quoted. The changes were measured by the ratio of intensities of respective peaks in the pyrene emission spectrum [36-38] or fluorescence anisotropy [39,41,42]. This paper presents also results of the recent luminescence research of sol-gel transition dynamics using other chromophores, e.g. rhodamine G6 [44,45], ruthenium complex [47], oxazine [48], 1,4-dihydroxyanthraquinone [49], 3,3-diethyloxadicarbocyanines [50] and quinine [51].

The silane gel has properties which are important and interesting from the point of view of its application, i.e. transparency, porosity, thermal stability, and ability to form different carrier forms, e.g. powder, film or fibre [1]. So, in the final part of this paper the examples of applications of these carriers in the newest probes, i.e. chemical optical sensors [57-63], biochemical optodes [64-72], and immunocolumns [75-77] are presented.


Wiadomości Chemiczne, 2000, 54, 435.
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PHARMACOPHORE GROUPS OF THE ARYLPIPERAZINE LIGANDS OF SEROTONIN 5-HT1A RECEPTORS

Anna Wesołowska

Zakład Badań Nowych Leków, Instytut Farmakologii PAN, ul. Smętna 12, 31-343 Kraków


Of different subpopulations of G-coupled serotonin (5-HT) receptors, in the past decade the utmost attention has been focused on the 5-HT1A subtype. This review is concerned with the structure-activity relationships of some 5-HT1A receptor ligands belonging to the 1-arylpiperazine class.

Literature data show that NAN-190, MM-77 and BMY 7378 which contain a 1-(o-methoxyphenyl)piperazine (1-MeOPhP) fragment have a very high 5-HT1A affinity and act as postsynaptic 5-HT1A receptor antagonists [21, 25, 26]. It has been shown that the basic nitrogen atom and methoxy group in the arylpiperazine fragment are desired features of the structure for both the affinity and postsynaptic antagonism at 5-HT1A receptors, since (I) replacement of the 1-MeOPhP fragment by 1,2,3,4-tetrahydroisoquinoline (THIQ) causes a dramatic loss of the 5-HT1A affinity (cf. 1 vs BMY 7378, 2 vs MM-77, 3 vs NAN-190) (Fig. 6) [23, 32, 36, 37], (II) modifications of the amide fragment (cf. MM-77 and MM-55 vs NAN-190) (Table 1) have no significant effect on their functional activity; like NAN-190, MM-77 and MM-55 are postsynaptic 5-HT1A antagonists [36, 38], and (III) replacement of the 1-MeOPhP fragment by the 1,2,3,4-tetrahydropyrazino[1,2-a]indolo system results in a significant loss of the 5-HT1A affinity and a lack of in vivo activity (cf. 4 vs NAN-190) (Fig. 7) [36, 38]. Therefore it may be assumed that the 1-MeOPhP fragment present in the postsynaptic 5-HT1A antagonists plays a major role in the formation of a bioactive complex with 5-HT1A receptors.

Another 5-HT1A ligand, buspirone - a second-generation anxiolytic - which contains a 1-(2-pyrimidynyl)piperazine (1-PP) fragment, is a postsynaptic 5-HT1A partial agonist. It is generally accepted that the buspirone molecule is recognized by the 5-HT1A receptor due to the presence of 1-PP [30, 31, 32]. In other words, the 1-PP fragment of buspirone fulfills the minimal structure requirements defined by Hibert et al. (Fig. 4) [30, 31] for the interaction with the 5-HT1A binding site, one being the presence of an aromatic ring, and the other the presence of a basic nitrogen atom at a distance of 5.2-5.7 D. On the other hand, the terminal imide moiety offers an additional site of interaction with the 5-HT1A receptor, which results in a greatly enhanced affinity of buspirone in relation to 1-PP [3, 15, 30, 31, 32, 34, 35, 37]. The buspirone molecule is modified by replacing the 1-PP fragment with THIQ (compound MM199) (Fig. 6). Buspirone and MM199 are equipotent 5-HT1A ligands; moreover, MM199 has essentially the same functional profile at postsynaptic 5-HT1A receptors as does buspirone. Both these compounds are classified as partial agonists of postsynaptic 5-HT1A receptors [37]. Furthermore, like buspirone, MM199 shows an antidepressant- and an anxiolytic-like activity in animal models. Its effects are antagonized by (S)WAY 100135, a 5-HT1A receptor antagonist, which suggests that potent antidepressant- and anxiolytic-like effects of MM199 are mediated by activation of 5-HT1A receptors [50].

The obtained results permit a general conclusion that the basic nitrogen atom and the terminal bulky cycloimide moiety, but not the 2-pyrimidinyl group, are pivotal features of the buspirone structure, being directly involved in the formation of a bioactive complex with 5-HT1A receptors [37].


Wiadomości Chemiczne, 2000, 54, 457.
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DINITROAMINE (DNA), COMPOUNDS WITH -N(NO2)2 GROUP AS POTENTIAL COMPONENTS OF ENERGETIC MATERIALS.

Michał Syczewski, Iwona Cieślowska-Glińska

Zakład Materiałów Wysokoenergetycznych, Wydział Chemiczny, Politechnika Warszawska, ul. Noakowskiego 3, 00-664 Warszawa.


The methods of preparation and properties of dinitroamine HN(NO2)2 and its salts have been described. The use of many simple or complex salts of DNA can be considered as oxidizing components in the compositions of energetic materials. On the basis of DNA structure it was deduced that it would be possible to prepare ionic as well covalent organic compounds with -N(NO2)2 group. These compounds can be energetic materials alone as well as salts of DNA with organic cations and as complexes with organic ligands. High degree of interest in the synthesis and properties of DNA, its salts and new compounds with -N(NO2)2 group has been recently observed in literature.

Main factors which accelerate studies on the synthesis and properties of DNA derivatives are the potential of their applicability and also the progress in our knowledge. DNA is a strong acid, its anion possesses ambident structure:

Wzór

 
therefore, two types of salts can be formed. Similarly, alkylation of DNA leads to N- or O-alkyl derivatives.

Mercury dinitramide Hg(N3O4)2 was extremely interesting . It is covalent compound (O-salt) in a solid state as well as in the solution in nonpolar solvents. In polar solvents it dissociates forming mercury (II) cation and N3O4 anion. Hg(N3O4)2 can be useful reagent in organic synthesis similarly to other inorganic derivatives of mercury .


Wiadomości Chemiczne, 2000, 54, 473.
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DEGRADATION OF POLYCHLORINATED BIPHENYLS

Stanisław Gryglewicz

Instytut Chemii i Technologii Nafty i Węgla Politechniki Wrocławskiej, Ul. Gdańska 7/9, 50-344 Wrocław


Polychlorinated biphenyls ( PCBs ) do not bring about a sharp toxical effect in mammalian organisms. However, owing to the tendency of PCBs accumulation in the environment, low biodegradability and potential dangerous consequences for human health generating in long-term period, the efforts leading to PCBs elimination from environment are reasonable. In spite of the discontinuation of PCBs production, there are still their emission sources, i.e. mainly electrical facilities filled in insulating fluid, which contains polychlorinated biphenyls of high concentration.

In this paper the bases of PCBs synthesis were discussed. The principle of nomenclature of working fluids produced on the base of PCBs and their main physicochemical properties were also given [8]. In the second part of the paper the structure and chemical reactivity of polychlorinated biphenyls compounds were discussed, in particular, their inert behaviour in nucleophilic substitution reactions [12,13]. Moreover, the theoretical bases of PCBs degradation methods including chemical, physicochemical and biological processes were described. It was emphasised that PCBs degradation methods and remediation of PCB contaminated materials are required to be environmentally safe.

An efficient degradation method of liquid and solid materials showing high PCBs concentration is their incineration in a special furnace [41,43] with precisely controlled technological regime as well as with the use of a plasma torch [48] to avoid dioxine formation via recombination of uncompleted combustion products. It was indicated that PCB contaminated petroleum derived products are of the secondary potential source of PCBs propagation in the environment. For this kind of products, catalytic hydrogenation appears [36] to be a particularly interesting means of dechlorination without destroing the initial material. Also the treatment of hydrocarbon mixture with colloidal suspension of metallic sodium offers an attractive dechlorination potential. The mechanism of this reaction is not well known. Probably, the reaction proceeds through aryne mechanism.

Attempts to remediate PCB contaminated waters by means of electromagnetic radiation in the presence of suitable catalysts [52,53] were mentioned as well. Finally, biological degradation methods of PCBs removal particularly from contaminated water and sewage were described [60].


Wiadomości Chemiczne, 2000, 54, 499.
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NOTATKI CHAOTYCZNE XXVIII. O "NIEDOODKRYCIACH"

Ignacy Z. Siemion

Wydział Chemii Uniwersytetu Wrocławskiego, ul. F.Joliot-Curie 14, 50-383 Wrocław


Wiadomości Chemiczne, 2000, 54, 517.
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QUANTITATIVE CRITERIA OF AROMATICITY. Part II

Michał K. Cyrański, Tadeusz M. Krygowski

Uniwersytet Warszawski, Wydział Chemii, ul. L. Pasteura 1, 02-093 Warszawa


Aromataic character is manifested in p-electron systems by particular physicochemical properties: an increase of stability, averaging of bond lengths, particular magnetic properties and chemical reactivity preffering retention of the p-electron structure. These properties are used for definitions of quantative measures of aromaticity (indices of aromaticity) (Tab. 1). In principle they do not always predict the aromatic character in a uniform way. Additionally each of the used criteria is biased by some inadequacies or lack of generality. The energetic criterion defined as resonance energy or aromatic stabilisation energy measures the total aromaticity and strongly depends on the choice of reference states and/or reactions (tab. 3). The same is true for the magnetic criterion - exaltation of the diamagnetic susceptibility. Geometric parameters seem to be the most general and may be used for estimation of both local and global aromatic character. Each of the criteria may be used providing a proper reference state can be defined. Application of variously defined indices of aromaticity is critcally discussed.


Wiadomości Chemiczne, 2000, 54, 533.
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HOMOGENEOUS HYDROGENATION OF ARENES

Andrzej F. Borowski

Zakład Karbochemii Polskiej Akademii Nauk, ul. Sowińskiego 5, 44-121 Gliwice


Catalytic activity of soluble metal complexes in homogeneous hydrogenation of aromatic hydrocarbons has been reviewed based on 86 articles.

The catalysts of different structural types (e. g. metal carbonyls, complexes containing coordinated arenes, allyls, dihydrogen ligands) as well as some complexes of the early transition metals (Nb, Ta) are catalytically active in reduction of aromatic rings of mono and polynuclear aromatic hydrocarbons. Where available, mechanisms of hydrogenation reactions have been presented. Most of the proposed mechanisms involve coordination of arene in an h4-mode. E. g. benzene hydrogenation requires coordination of the substrate as h6, h4 or h2-arene. Transition h6 ®h4 leads to a noncoplanar C6 skeleton and a highly disturbed aromatic system lowers the aromatic resonance stabilization energy (bent arene) and provides a driving force for arene ring hydrogenation.

From among studied complexes the highest activity in benzene hydrogenation has been observed in the presence of [{Rh(h5-C5Me5)Cl2}2] in homogeneous systems [28] and in the presence of a water-soluble complex [(h6-C6H6) 2Rh2Cl4]  [53] used in two-phase system [53]. [(h6-C6Me6v)Ru(m-H) 2 (m-Cl)Ru(h6-C6Me6)]Cl  [39] turned out to be the most active naphthalene hydrogenation catalyst, while the best results in anthracene reduction has been obtained using the dihydrogen complex [Ru(H) 2 (H2) 2 (PCy3) 2] [48].

Some aspects of homogeneiety control of arene hydrogenation reactions catalysed by metal complexes are discussed.


Wiadomości Chemiczne, 2000, 54, 565.
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CARBONACEOUS DEPOSITS AND THEIR INVESTIGATIONS BY VARIOUS TECHNIQUES

Jacek Góralski, Jacek Grams, Iwona Ludomirska, Tadeusz Paryjczak, Izabela Rzeźnicka

Instytut Chemii Ogólnej i Ekologicznej Politechniki Łódzkiej, 90-924 Łódź, ul.Żwirki 36


The reaction of organic compounds on solid catalysts can be accompanied by the formation of heavy by-products which can form a carbonaceous deposit on the surface and cause deactivation. Coke is an intractable, poorly defined material, changing in nature and composition with almost all possible reaction variables [1-14].

Studying the location of coke and its nature requires sophisticated techniques. Transmission electron microscopy (TEM) can be used to present coke directly (Fig.1) [17-26], while electron loss spectroscopy (EELS) [27] and X-ray photoelectron spectroscopy (XPS) [22, 29, 30] can provide analytical and structural information (Fig.2).

It is a well-known fact that strongly bonded species, containing carbon or sulphur, may induce complex changes in the structure of a metallic substrate. These changes may have an impact on the catalytic properties. The influence of coke deposition on catalyst structure was studied by means of the X-ray diffraction method (XRD). The evidence of internal coke ( coke deposited inside the channel system) is given by XRD patterns [31, 32]. 129Xe NMR is also a technique which can provide information about the location of the coke [44-50].

Coke produces a decrease in catalytic activity by two mechanisms: active site suppression or pore blocking. Both deactivation modes may occur simultaneously, although one of the two mechanisms is usually predominant. The loss of sorption capacity of coked catalysts (Fig.3) can help us to find out which deactivation mode has occurred [31, 37-42]. The increase in sorption capacity with increasing regeneration time corresponds to a successive removal of coke [45].

The technique of temperature programmed oxidation (TPO) with either evolved gas (Fig.6) or gravimetric analysis (TGA) is often employed to investigate coke deposition on catalysts. Details of the proximity of coke to metal and nonmetal sites or the nature of coke are then inferred from the position of peaks in the resultant TPO profiles [21, 52-70]. The shape of these profiles can be affected by coke particle size and morphology [71, 72]. Currently TPO is performed with the following detection methods: determination of CO2 by a thermal conductivity detector [53], quantification of CO2 with a mass spectrometer [55, 60], methanation of CO2 [56], monitoring temperature increment above a reference sample in differential thermal analysis (DTA) equipment [29, 32, 37, 61] or measurement of weight loss in thermal gravimetric analysis (TGA) equipment [49, 62].Thermograms of fouled catalysts can be divided into distinct regions. This indicates an inhomogeneous distribution of coke formation. Relatively less bulky carbonaceous compounds, which desorb at lower temperature range are termed 'soft coke'. More bulky carbonaceous compounds, which desorb at higher temperature, are referred to as 'hard coke' [32, 49].

In recent years, 13C NMR in conjunction with proton cross-polarization (CP) and magic-angle spinning (MAS) has emerged as a powerful tool for studying the nature of coke formed during hydrocarbon conversion over catalysts [15, 29, 45, 48, 79, 81]. Thanks to this method, valuable information such as the state and mobility of adsorbates, details of the regulated guest/host interactions [48] and the nature and distribution of the coke can be obtained [83]. 13C NMR has the unique ability to directly determine the distribution of aromatic, aliphatic and other carbon types present (Fig.7) [45]. IR spectroscopy has also been used to obtain information about the nature of the species present in the coke deposited on different zeolites [31, 37, 79, 84, 85] as well as on other catalysts [86]. The selective removal and transformation of carbonaceous compounds during reactivation were examined by means of IR combined with GC, TGA and NMR spectroscopy [45].


Wiadomości Chemiczne, 2000, 54, 591.
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In vitro selection of nucleic acids

Barbara Nawrot

Zakład Chemii Bioorganicznej, Centrum Badań Molekularnych i Makromolekularnych PAN, ul. Sienkiewicza 112, 90-363 Łódź


In vitro selection of nucleic acids (Systematic Evolution of Ligands by Exponential Enrichment - SELEX) is the selection technique which, from the library of randomised or degenerated RNA or DNA molecules, allows the isolation of nucleic acids with expected biochemical properties [1-4]. Repeated cycles of selection and amplification have been used to isolate sequences of nucleic acids (aptamers) that bind with high affinity specific molecular targets - proteins [2] or low molecular weight ligands [3]. This method allows also to isolate a number of nucleic acids with catalytic activity and thus to generate new ribozymes [5-9] and deoxyribozymes [10]. SELEX is an useful tool of molecular biology and bioorganic chemistry for developing new therapeutic agents [11], as well for the insight in function of RNA in molecular evolution [12, 13] and RNA World hypothesis [14, 15].


Wiadomości Chemiczne, 2000, 54, 615.
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MICROCYSTINS IN WATER RESERVOIRS

Piotr Gajdek

Zakład Fizjologii i Biologii Rozwoju Roślin, Instytut Biologii Molekularnej, Uniwersytet Jagielloński, Al. Mickiewicza 3, 31-120 Kraków


Many species of cyanobacteria forming blooms in eutrophic waters produce toxins. They are cytotoxins, neurotoxins, hepatotoxins and dermatotoxins [1-10]. The hepatotoxins can be divided into microcystins and nodularins, cyclic hepta- and pentapeptides respectively. About 60 microcystins have been characterized and the most common is microcystin-LR (Fig. 1), but their chemical structure may be also different [3, 4, 9, 12]. Since a long time cyanobacterial toxins have been the reason of lethal poisonings of wild and domestic animals and health problems of humans in different regions of the world [1, 2, 5, 6, 9, 13]. In 1996 in Brazil about 60 haemodialysis patients died after getting a lethal microcystin dose intravenously [14, 15]. The most frequent signs of poisoning are anorexia, general weakness, diarrhoea and vomiting [5]. Microcystins repeatedly uptaken by organisms in trace amounts contribute to the development of cancer as a result of their inhibition of protein phosphatase 1 and 2A [17]. There are epidemiological data indicating high rates of cancer in China due to long term exposure to cyanobacterial toxins in water [20]. World Health Organization proposed 1 microgram per litre as a guideline value for maximum acceptable level of microcystin-LR or its equivalents in drinking water [13]. Microcystins are chemically very stable and can not be decomposed by acid, alkaline or boiling. In field conditions their degradation is minimal [21]. They are also difficult to decompose in water treatment processes. Conventional water treatment methods are not sufficient, while activated carbon filtration or ozonation makes them more effective [23], but still trace amounts of microcystins pass the full-scale treatment [22]. Many methods of degradation or chemical modification of microcystins have been devised. Unfortunately, despite large body of research work cyanobacterial toxins are still dangerous, especially in drinking water reservoirs [21]. In Poland, the cyanobacterial blooms in drinking water reservoirs constitute a serious problem, especially for large agglomerations. For instance in summer 1993 in Sulejowski reservoir being a drinking water source for the city of Łódź the microcystin content in a cyanobacterial bloom was in the range of 40 - 117 mg/g dry mass of phytoplankton [6], reaching in the following years the value of 427 mg/g dry mass of phytoplankton, which was in the years 1995 and 1996 on the average 5.7 mg/L [9]. In the samples gathered in 1996 in Jeziorsko and Zalew Włocławski the average microcystin content was around 300 mg/g dry mass of phytoplankton [9, 10]. The presence of cyanobacterial toxins in Polish lakes and water reservoirs establishes new problems for Polish waterworks and laboratories dealing with water quality analysis [9]. This article contains many hints on construction of experimental set-ups for the determination of cyanobacterial toxins in water reservoirs, in particular sampling methods [24], choice of filters for separation of cyanobacterial cells [31], parameters in sample enrichment by means of solid-phase extraction [33, 35, 37] and analysis with high performance liquid chromatography [31, 35, 42], detection methods [44 - 46, 50], etc.


Wiadomości Chemiczne, 2000, 54, 637.
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THE MULTIMEDIAL TEXTBOOK IN CHEMISTRY TEACHING

Hanna Gulińska, Andrzej Burewicz

Zakład Dydaktyki Chemii, Wydział Chemii Uniwersytetu im. Adama Mickiewicza, ul. Gunwaldzka 6, 60-780 Poznań


A review of current textbooks on the teaching of chemistry allows us to state that an ever-growing number of them are not only very thoroughly illustrated, but are supplemented by many didactic media. The elements supporting the textbook should be treated as unique elements added at the time that the text itself was already in existence. Quite a different teaching approach is found in the case of textbooks created from the outset with the idea of using many medial codes of presenting information and having a unitary structure with specially prepared supporting media (slides, overhead transparencies, videocassetes). In the situation where the supporting media comprise the fundamental element of the audio-visual textbook, taking over a considerable amount of its content, the preparation of the appropriate materials takes on the central role in creating the book itself.

Preparation of a textbook fulfilling the above mentioned criteria encounters difficulties primary of a technical nature. The hope for overcoming them lies over more often in multimedial textbooks. Working with multimedial textbook of this type should place the student in a research situation, creating conditions for conducting independent reseach - seeking answers to posed questions and providing solutions to theoretical and practical problems. Substitution of the traditional textbook with multimedial one opens several hitherto unused avenues of action made available through the new educational technology.

In Poland, multimedial textbooks have yet to be developed, which would be devoted to the teaching of chemistry at the high school and junior high school level (from 13 to 18 years) and meeting the standards of the of the curriculum. These considerations have resulted in our developing research aimed at an evaluation of the effectivness of chemistry teaching supported by multimedial programs. The latter are aimed at intellectual and manual motivation of the students through emotional engagement and the way they reinforce information retention and provide acceptable methods of systematizing information elicited by the structure of the multimedial programs themselves.

In considering the resuts of our research, confirming the possibility of a considerable improvement in the effectiveness of teaching natural science subjects by means of multimedia, we undertook activities aimed at developing multimedial textbooks for the teaching of chemistry at various educational levels. This undertaking of considerable scope is initiated by the textbook Chemistry with Elements of Ecology by H. Gulińska and A. Burewicz, aimed at the high school level of teching.

The textbook Chemistry with Elements of Ecology is composed of three parts (each on two CD-ROMs) and contains the following subject area groups:
Part 1 - "Chemistry Fundamentals",
Part 2 - "Types of Inorganic Compounds",
Part 3 - "Carbon and Its Compounds"


Wiadomości Chemiczne, 2000, 54, 651.
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"CHEMISTRY AND ART". PROJECT IN PRIMARY SCHOOL

Romuald Piosik

Uniwersytet Gdański, Wydział Chemii , Zakład Dydaktyki Chemii, ul. Sobieskiego 18, 80-952 Gdańsk


The students from the eight grade of the Primary School No 1 in Gdynia chose the project "Chemistry and Art". It was covered in 12 lessons during 6 weeks, combining two 45-minute lessons each week. 18 students took part in the project.

During the first session the students got acquainted with the work methods, split into three groups and answered the preliminary questionnaire. During the second session the students received the following pigments by themselves:

blue - Prussian blue (Fe4[Fe(CN) 6]3).

green - malachite (CuCO3Cu(OH) 2),

white - barium sulphate(VI) (BaSO4) or titanium(IV)oxide (TiO2),

red - iron(III) oxide (Fe2O3) or red lead (Pb3O4),

yellow - lead(II) chromate(VI) (PbCrO4).

In the third and fourth sessions they made the following paints from the previously received pigments:

water-colours (group 1),

oil-paints (group 2), and

tempera (group 3),

and prepared appropriate undercoats for the paints. In the fifth session each group used the paints to paint whatever they desired. At the same time the students widened their knowledge of naturally available pigments, chemical and physical properties of the undercoats, nature of light and colours, history of painting and well known painters who used water-colours, oil-paimts and tempera. The students also conducted interviews with painters and visited an art gallery.

During the sixth session they summarized the results in each group, shared information about the methods of preparation of the various kind of paint and filled in the questionnaire. The students' paintings were also exhibited.


Wiadomości Chemiczne, 2000, 54, 677.
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NOTATKI CHAOTYCZNE XXIX. O DEFINICJI CHEMII I PEWNEJ NIEDAWNEJ DECYZJI KOMITETU BADAŃ NAUKOWYCH

Ignacy Z. Siemion

Wydział Chemii Uniwersytetu Wrocławskiego, ul. F.Joliot-Curie 14, 50-383 Wrocław


Wiadomości Chemiczne, 2000, 54, 691.
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NEW DIRECTIONS IN THE GUEST OF ANTI-CANCER AGENTS.

Elżbieta Mikiciuk-Olasik, Katarzyna Błaszczak-Świątkiewicz

Zaklad Chemii Farmaceutycznej i Analizy Leków Akademii Medycznej w Łodzi, ul. Muszyńskiego 1, 90-151 Łódź


Cancer chemotherapy over twenty years has been under extremely intensive investigation. Failure in the treatment of neoplasms is due to characteristic fe-atures of cancer cells. Their structure delays and decreases the efficacy of drugs administered orally or intravenously. Therefore, greater emphasis is placed on the development of new molecular studies. The development of particular molecular diagnostic methods is based on new advances in immunology, genetics and nuclear medicine.

Nuclear medicine concentrates on the diagnostics and treatment of various diseases, including neoplasms treated by means of radiopharmaceuticals [5]. The isotope most commonly used as a source of g radiation for radiopharma-ceuticals is technetium (99mTc). The complexes of this radiotracer (e.g. 99mTc-HM-PAO - Fig. 1, 99mTc-CB-PAO - Fig. 2, 99mTc-ECD - Fig. 3) are widely used for brain imaging. These compounds indicate areas of normal blood supply in the brain, but do not enter hypoxic tumour cells.

The differences in oxygenation level between normal and cancer cells is key strategy used not only in the diagnostics, but also in the treatment of neoplasms. Some compounds [quinone antibiotics (mitomycin C - Fig. 4), nitroimidazoles (metronidazole - Fig. 5, misonidazole - Fig. 6), tirapazamine - Fig. 8 are known as hypoxia selective agents activated in low oxygen concentrations [8-10]. Another strategy used in anticancer therapy aims at the inhibition of angiogenesis in the tumour [2-3]; other methods limit the growth of tumour - these include use of inhibitory enzymes such as telomerase inhibitors (phosphorothioate oligonucleotides - Fig. 13, cisplatin - Fig. 14) [15-22] and polyamine metabolism inhibitors (DFMO - Fig. 16, MGBG - Fig. 17) [23].

Valuable antineoplastic drugs originate from natural sources. Currently, the derivatives of acronycine - Fig. 26 and spongiostatin - Fig .27 are being investigated. Natural compounds with a documented anticancer activity include, for example, taxol - Fig. 23, etopozide - Fig. 24A and tenipozide Fig. 24B [24-25, 27].

New directions in the research of new compounds for use in the diagnostics and treatment of neoplastic diseases are closely related to the development of molecular studies, which offer explanation of complex patophysiology of tumours on molecular level. Also. medical chemistry plays an important role in modern investigation methods, such as molecular modelling.


Wiadomości Chemiczne, 2000, 54, 705.
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ADVANCES IN STEREOSELECTIVE SULFOXIDATION

Jacek Skarżewski, Elżbieta Ostrycharz

Instytut Chemii Organicznej, Biochemii i Biotechnologii, Politechnika Wrocławska Wyb. Wyspiańskiego 27, 50-370 Wrocław


The preparation of optically active sulfoxides, useful chiral auxiliaries and synthetic building blocks is reviewed. Beginning with the progresses in the non-oxidative synthesis of chiral sulfoxides [6-11], the main part of the survey is devoted to the advances in stereoselective oxidation of the easily available prochiral sulfides.

Firstly, the diastereoselective oxidation of sulfides containing other chiral center is discussed. Remarkable selectivities were obtained in the oxidation with MCPBA [13, 14], t-BuOCl [17], and (NaOCl, cat. TEMPO) [19-21]. In the next part the enantioselective oxidation processes are considered. The material is organized according to the character of the oxidant: chiral-stoichiometric methods and chiral catalytic methods. Among stoichiometric chiral oxidants, some of the most important are the Davis oxaziridines. An essential improvement in enantioselectivity was gained by the application of N-(phenylsulfonyl)-3,3-dichlorocamphoryloxaziridine [27], [(8,8-dimethoxycamphor)sulfonyl]oxaziridine and ethylene ketal of the respective 8-oxocamphor derivative [29, 30]. Much progress was also observed in oxidations with the Ti(IV)-supported chiral reagents. The Kagan and Modena methods were further elaborated. The highest e.es were observed using Ti(Oi-Pr)4/DET/H2O in 1:2:1 ratio [33] or Ti(Oi-Pr)4/DET/i-PrOH (1:4:4) + molecular sieves [34], both with cumyl hydroperoxide. The non-linear enantioselectivity effects (NLE) were found for these systems [36] as a proof for involvement of the chiral dimeric Ti-species. Uemura made an important modification to this oxidant by replacement of diethyl tartrate with Binol [44]. Also chiral 1,2-diols and C3-symmetric triols were used as chiral inducers with the Ti- supported system [46-48]. The other approach exploited chiral hydroperoxide obtained via biooxidation of hydrocarbon. Thus prepared oxidant gave enantioselective sulfoxidation with ca. 80 % e.e. [51].

In the field of catalytic sulfoxidations an important advancement was made by Bolm and Binewald who discovered the system active even at the 0.01 % mol level of chiral inducer. The catalyst was in situ formed from vanadyl acetylacetonate and (S)-(-)-N-(3,5-di-tert-butylsalicylidene)tert-leucinol and 30% aqueous hydrogen peroxide was applied as a stoichiometric oxidant. The results attained were within 70-80 % e.e. level for simple alkyl aryl sulfoxides, [57] and over 91 % e.e. for the oxidation of di(tert-butyl) disulfide [59]. The catalytic system was further optimized and 75-95 % e.es were observed for the oxidation of thioanisole, 2-aryl-1,3-dithianes and 1,2-bis(arylthio)ethanes [61]. The other successful catalytic oxidant was the Uemura system (Ti(Oi-Pr)4/Binol/H2O, 5 % mol of Binol). In this version the system gave truly enantioselective oxygen transfer (98 % e.e.) [64].

Many papers have been published on the application of the biological oxidants and the use of such methods is a feasible alternative to the chemical ones [12, 66, 67]. In particular, the microbiological systems containing fungi Helmithosporium were successfully applied for the preparative oxidation of prochiral thioketals and thioacetals, which could not be oxidized by purely chemical means [71]. Also various bacterial strains of Pseudomonas sp. were used and, e.g. hexyl methyl and cyclohexyl methyl sulfides were oxidized to the respective sulfoxides with high enantioselectivity [77]. Bacterial cyclohexanone monooxygenase was studied most widely among all the purified enzymes used in sulfoxidations [67, 78-85]. Asymmetric sulfoxidation was also investigated with hydrogen peroxide and vanadium bromoperoxidase and high enantioselectivities were obtained particularly for cyclic sulfides and those having a carboxylic group [88].


Wiadomości Chemiczne, 2000, 54, 725.
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SELECTED APPLICATIONS OF BORNANE-10,2-SULTAM (OPPOLZER'S SULTAM) IN ASYMMETRIC ORGANIC SYNTHESIS.

Aneta Szymańska, Ewa Wieczerzak i Leszek Łankiewicz

Katedra Chemii Organicznej, Wydział Chemii, Uniwersytet Gdański ul. Sobieskiego 18, 80-952 Gdańsk


Among many methods of asymmetric synthesis, the second-generation reactions i.e. the ones applying chiral auxiliary to generate new chiral centers are the most popular and widely used. In the last two decades many new and highly effective chiral auxiliaries were described. Bornane-10,2-sultam, introduced by Oppolzer and co-workers [1], is one of the most popular and most effective in generating new chiral centers.

Utility of bornane-10,2-sultam is due to:

- simplicity of a method of its synthesis from the natural, cheap source - camphore (Scheme 1) [2-9],
- high yield of connecting to prochiral substrates (Scheme 2),
- almost quantitative asymmetric induction,
- straight-forward removal of the formed product from bornane-sultam, which does not cause the loss of chirality at a new chiral center ,
- its high recovery after removal of product and possibility of multiple applications.

One of the most popular reactions studied in asymmetric synthesis is aldol condensation. This reaction was also studied with application of bornane-10,2-sultam (Schemes 4 and 5, Tables 1 and 2) [18-21]. Depending on the type of used base and Lewis acid either pure "cis" or "trans" isomer can be obtained. The chemical yields of the reactions were also high (50÷90%)

N-acylated derivatives of bornane-10,2-sultam have been revealed also as facile precursors of chiral alkylated carboxylic acids, ketones, aldehydes and alcohols (Schemes 7 and 7, Tables 3 and 4) [10, 15, 22, 23]. Diastereoisomeric excesses were in many cases above 99% and chemical yields were also very good (in most cases above 80%). Alkylation step can be also applied for asymmetric synthesis of a-amino acids (building blocks of peptides) but it is necessary to use N-[bis(methylthio)methylene]glycine methyl ester for acylation of the sultam. Quite nice selection of amino acids in optically pure form can be obtained by this method (Schemes 8, Table 5) [24-31].

Other possibilities of the sultam usage arise from nucleophilic and electrophilic amination reactions (Schemes 9-11, Tables 6-8) [32-43]. These methods were applied to obtain amino, azido, hydrazino and N-hydroxyamino acids with high chemical yield and optical purity.

Applications of bornane-10,2-sultam derivatives with a,b-unsaturated side chain are also very wide in asymmetric organic synthesis. One of the most popular reaction involving unsaturated compounds is Diels-Alder's cycloaddition. (Scheme 11-13) [6, 44-48]. Cyclic compounds formed during this addition are mostly endo-structures. Stereoselectivity is very high (higher than 90 %) and depends on a type of Lewis acid used (Table 9). Another interesting precursor in this kind of addition reaction seems to be the sultam derivative obtained by the modification with glyoxalic acid [49-53]. Its application can lead to piran derivatives and substrates of sugar moieties (Scheme 14).

N-acylated with a,b-unsaturated carboxylic acids sultam derivatives are also good substrates for carbonyl compounds stereoselectively substituted on a- or/and b-carbons (aldehydes, ketones, carboxylic acids) as well as alcohols. For preparation of optically active a,b-disubstituted compounds either Grignard's reagents (Scheme 15, 16 and Table 10) [60-62] or Gilman's reagents (Scheme 17, 18 and Table 11) [62-65] can be applied with diastereoselectivity in range 70÷95 %.

Other possibilities of the "unsaturated" sultam derivatives usage arise from reactions with "hydrogen sources" or oxidation agents. Asymmetric hydride addition (Scheme 19 and Table 12) [66, 67] or catalytic hydrogenation (Scheme 20 and Table 13) [68] leads to a,b-disubstituted chiral compounds with good yield and stereoselectivity. Oxidation of double bond, on the other hand, is facile method for obtaining 1,2-diols - superior substrates for ketones, acetals and sugars (Scheme 21 and 22) [69-73].


Wiadomości Chemiczne, 2000, 54, 759.
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INTERFACIAL FREE ENERGY AND FREE ENERGY OF ADSORPTION AND MICELLIZATION OF SURFACE ACTIVE AGENTS

Bronisław Jańczuk, Wiesław Wójcik, Anna Zdziennicka

Zakład Zjawisk Międzyfazowych Wydziału Chemii UMCS w Lublinie, pl. Marii Curie-Skłodowskiej 3, 20-031 Lublin

Maria Luisa González-Martín, José Morales Bruque

Departamento de Física, Universidad de Extremadura, Avda. De Elvas s/n, 06071 Badajoz, Espana


This paper reviews the results of investigations of the surface free energy of surfactants and the correlation between hydrophobic group of surfactant-water and hydrophilic group of surfactant-water interfacial free energy and standard free energy of adsorption at water-air (oil) interface and standard free energy of micellization.

The surface free energy of the hydrophobic and hydrophilic group of the surfactants is considered separately. The van Oss and co-workers' approach to the interfacial liquid-liquid and solid-liquid free energy used for the energy determination has been described. This approach treats the surface free energy of a solid and a liquid as the sum of the Lfshitz-van der Waals and Lewis acid-base components. The acid-base component of the surface free energy depends on the electron-acceptor and electron-donor parameters of this energy. Different determination ways of the surface free energy components and parameters of the hydrophobic and hydrophilic group of the surfactants are shown. The usefulness of the Young equation and adsorption data of n-alkanes on solid surface for determination of the Lifshitz-van der Waals component and electron-acceptor parameters of the acid-base component of the hydrophilic group of the surfactants is presented.

On the basis of the surface free energy components and parameters of the hydrophobic and hydrophilic group of the surfactants and recently modified DLVO theory, the free energy of interaction between molecules or ions of the surfactants through the water phase and the free energy of removing surfactant molecules or ions from the water phase to air or oil phase can be predicted. The modified DLVO theory treats the interaction between molecules or particles through the liquid phase as the sum of Lifshitz-van der Waals, acid-base and electrostatic interaction components, which details are described for the systems including ionic or nonionic surfactants. The free energy of interaction can be used for prediction of the standard free energy of adsorption and micellization of the surfactants if the contactable area of the molecules or ions of the surfactants is known. Different ways of the contactable area between the hydrophobic and hydrophilic group of the surfactants and between groups and water molecules are presented. The calculated values of the free energy of interactions of the surfactants through water phase are compared to the standard free energy of micellization and the standard free energy of the adsorption of surfactants at water-air (oil) interface. For this purpose the determination of the standard free energy of adsorption from isotherms of adsorption of the surfactants and their standard free energy of micellization is also described.


Wiadomości Chemiczne, 2000, 54, 793.
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MESOPOROUS MOLECULAR SIEVES, SYNTHESIS AND PROPERTIES

Stanisław Kowalak, Krystian Stawiński

Wydział Chemii, Uniwersytet im. A. Mickiewicza ul. Grunwaldzka 6, 60-780 Poznań


The crystalline molecular sieves comprised almost exclusively microporous materials (zeolites and zeolite-like materials). The pore diameter of this materials was mostly in the range 0,3-0,8 nm. Despite a very narrow range of this diameter, which limits the number of molecules to be applied, the crystalline molecular sieves have attained a great commercial importance for many industrial processes (selective adsorption, ion-exchange, catalysis). The attention of many research groups was focused on syntheses of larger pore structures accessible for bulkier molecules. It was not sure, however, whether such structures could be achieved and if so, whether they would be satisfactory stable to be applied for practical purposes. The successful syntheses of crystalline structures of VPI-5, JDF-20, Cloverite, and UTD-1 indicated that extra-large diameters above 1 nm could be obtained. The structures, on the other hand, appeared not very stable and not easy to be synthesized and modified. Therefore, they have not been commercially applied. The important milestone in modem history of the molecular sieves was discovery of novel family of mesoporous, well organized materials in early ninetieths. This new family of the molecular sieves have been presented independently by Mobil and Toyota at the 9th International Zeolite Conference in Montreal. The first examples of the materials consisted exclusively of silica. Soon later the aluminosilicate mesoporous molecular sieves have been presented and then many other chemical compositions have been employed for synthesis of mesoporous molecular sieves. The materials of this kind are generally called M41S. The principle of synthesis of these materials shows some similarity with the preparation of zeolites and zeolite-like materials in respect to employing of the organic compounds as structure directing agents. The role of a template agent plays usually surfactants such as long alkyl chain amines, which form micelles in a solution. The micelle aggregates are then surrounded by inorganic precursors and the well organized array of voids (e.g. tubes) filled with surfactant molecules are formed due to condensation of an inorganic phase. The organic compounds are removed from the pores mostly by means of thermal treatment. A variety of surfactants applied allows to prepare various structures of different pore sizes (2-10 nm). The growing family of mesoporous molecular sieves contains many unique structures. The most common are: the hexagonal unit cell MCM-41, cubic MCM-48, lamellar structure MCM-50, although the number of defined structures is to date many times higher. Contrary to zeolites and other microporous molecular sieves the M41S are not crystalline materials. The XRD indicates usually only one or few reflections at very low range of 2-theta angle. The mesoporous molecular sieves show very high surface areas (usually above 1000 m2/g) and their adsorption/desorption isotherms of type IV often indicate a hysteresis loop. The transmission electron micrographs indicate a pore array in the lattice image. It has been hoped that the novel materials would show a similar catalytic activity as zeolites. These expectations have not been proven satisfactory so far. The catalytic activity of aluminosilicate mesoporous materials resembles rather activity of the amorphous aluminosilicates. The always growing variety of mesoporous structures and of their chemical compositions provides a chance of finding the materials of high and stable catalytic activity. The pore system of this materials is widely studied as a support accommodating the introduced catalytically active compounds. The mesoporous molecular sieves can be used for many other applications such as adsorption (storage of gases), matrices for microelectronic and optical devices, active fillers for polymers etc.


Wiadomości Chemiczne, 2000, 54, 817.
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MODEL QUANTUM-MECHANICAL CALCULATIONS IN CHEMISTRY

Jens Abildgaard, Poul Erik Hansen

Department of Life Sciences and Chemistry,, Roscilde University P.O. Box 260, DK-4000 Roskilde, Denmark; E-mail: POULERIK@ruc.dk


The paper reviews quantum chemical methods, ab initio as well as semiempirical methods based on the investigated molecules, salicylaldehede. The discussion is focused on determination of structure, calculation of vibrational frequencies, NMR chemical shifts and isotope effect on the latter.

The various schemes, restricted Hartree-Fock (RHF), RHF including second order electron correlation and a series of old and new density functional theory (DFT) methods are compared with well known semiempirical methods like AM1, PM3, CNDO, etc. Add to this the multitude of basis sets. The comparisons are made with respect to time and space requirements, convergence and quality of results.

A goal of the present paper is to find a molecular orbital method that in general will calculate both geometries and spectroslopic data as well.


Wiadomości Chemiczne, 2000, 54, 845.
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THERMODYNAMICS OF SATURATED SOLUTIONS AND SOLUBILITY

Henryk Buchowski

Zakład Chemii Fizycznej, Wydział Chemiczny, Politechnika Warszawska, ul. Noakowskiego 3, 00-664 Warszawa


The thermodynamic information given by solubility is very poor as the activity coefficient of the solute A can be calculated only (see Eqs (1) and (3)). To obtain more complete information a method of precise measurements of vapour pressure over saturated solutios has been elaborated [2]. The activity of the solvent B can be derived from vapour pressure data and the excess Gibbs' energy along the liquids can be determined with no adjustable parameters [10] as shown in Fig. 4. Theoretical equation for the activity of solvent in saturated solutions as well as for the solubility have been deduced [7]. The activity and the solubility depend on two constants l and b. The methods of determination of the constants from vapour pressure and solubility data are given [10]. The knowledge of l and b permits the calcuation of excess functions of mixing in saturated solutions [8] by Eqs (20)-(23). The analysis of excess functions gives evidence of the existence of a short-range order, i.e. a correlation of molecular orientations in the liquid A. The destruction of the correlation by mixing with the an inert solvent involves positive contributions to the excess enthalpy as well as to the excess entropy. The effect decreases the solubility. Sometimes both contributions cancel out and so called ideal solubility is observed. But the saturated solutions are pseudoideal only: excess Gibbs' energy is very small but excess enthalpy and excess entropy can be large. The thermodynamic properties of systems conforming to Schröder or Malesiński ideal solubility equations are discussed in detail. The test of thermodynamic cosistency of solubility data is formulated.


Wiadomości Chemiczne, 2000, 54, 889.
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NOTATKI CHAOTYCZNE XXX. O PAMIĘCI I JEJ PERFIDNYM WROGU: CHOROBIE ALZHEIMERA

Ignacy Z. Siemion

Wydział Chemii Uniwersytetu Wrocławskiego, ul. F.Joliot-Curie 14, 50-383 Wrocław


Wiadomości Chemiczne, 2000, 54, 915.
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PROFESOR MACIEJ WIEWIÓROWSKI THE CO-FOUNDER OF MODERN CHEMICAL RESEARCH IN POLAND

Wiesław Zygmunt Antkowiak

Uniwersytet im. Adama Mickiewicza, ul. Grunwaldzka 6, 60-780 Poznań


Professor Maciej Wiewiórowski is one of the most distinguished organic chemists in the world. He got his PhD in 1950 working on the chemical transformations of codeine with Professor J. Suszko at Poznań University. Next, he started developing his own research programme concerning the alkaloid composition of certain Lupinus species. Several of his students then are still continuing the structural and synthetic research in this topic.

At the end of the fifties, he spent quite some time on his first long-term post-doctoral fellowship working with Professor Leo Marion in the laboratory of the National Research Council of Canada in Ottawa, and it appeared to be the beginning of his fruitful collaborations with many outstanding scientists in the world in the subsequent years. When working in this foreign laboratory, he took the opportunity to become acquainted with many modern research techniques, especially column chromatography and IR as well as other spectroscopic methods, which enabled him to propagate and popularize these techniques in our country when he returned.

In the late sixties, being the Head of the Stereochemistry and Organic Spectrochemistry Division at the Adam Mickiewicz University in Poznań, he began to organize, under the auspices of the Polish Academy of Science, a new field of research in Poland, then undeveloped worldwide, concerning the synthesis of nucleic acids. He both gathered young scientists, giving them special training, and organized new laboratories outside the University. In the early seventies, he moved with his group to the tentative laboratories at Noskowskiego Street in Poznań, there systematically and intensively expanding this research center, which finally resulted in the creation of the Institute of Bioorganic Chemistry of the PASc, a leader in the scientific world in carrying out modern biochemical research in nucleic acid as well as in protein chemistry.

During recent years, already being retired, he is still very active in the life of the Institute , including carrying out research mainly on the reaction of nucleosides in a solid state.


Wiadomości Chemiczne, 2000, 54, 939.
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INFLUENCE OF THE PARTIAL ORDER OF MOLECULAR ORIENTATION ON THE HIGH RESOLUTION NMR SPECTRA.

Andrzej Ejchart* i Adam Gryff-Keller**

*Instytut Biochemii i Biofizyki PAN, ul. Pawińskiego 5A, 02-106 Warszawa.
** Wydział Chemiczny, Politechnika Warszawska, ul. Noakowskiego 3, 00-664 Warszawa.


Molecules of solute in the liquid phase can display partial orientation owing to the interaction of an anisotropic magnetic susceptibility tensor with an external magnetic field or/and to the interaction with anisotropic liquid crystal solvent. In the latter case orientation of the solvent molecules is caused by the magnetic field as well. Formal, statistic description of the solute molecular orientation is identical in both cases and it has been demonstrated without recalling to the Wigner rotation matrices. Since the orientation of solute molecules is not averaged out due to the rotational diffusion completely, several interactions, additional to the isotropic liquid phase, manifest in the NMR spectra, namely, dipolar nad quadrupolar interactions as well as anisotropic parts of chemical shifts (screening) and spin-spin couplings. Therefore, a number of structural molecular parameters, which depend on those interactions, become accessible. Determination of very accurate geometries of small organic molecules and the accuracy improvement of the NMR-derived structures of biomolecules are the most frequent applications of the NMR studies in anisotropic phases. Analysis of the NMR spectra of 3,5-dichlorphenylacethylene in the nematic solvent ZLI1169 has been presented as an example of the liquid crystal solvent application.


Wiadomości Chemiczne, 2000, 54, 949.
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HYDROGEN BONDED COMPLEXES OF UREA

Jerzy Polaczek, Wojciech Domanowski

Instytut Chemii Przemysłowej im. Prof. Ignacego Mościckiego, ul. Rydygiera 8, 01-793 Warszawa


Urea is a commercially available and relatively cheap chemical underestimated in practical use for chemical purposes. One peculiar property of urea is its ability to form hydrogen bonds with many organic and inorganic compounds, where it can play the role of both a proton donor and a proton acceptor. The hydrogen bonds present in urea complexes are revealed by some characteristic points in equilibria curves, especially in the liquidus curves and also in the courses of some physical property curves like viscosity, refractive index or dielectric constant versus composition of a binary mixture. Hydrogen-bonded complexes can be practically applied to purify and to separate organic substances that are able to form hydrogen bonds or to remove contaminants that have such properties. The main advantage of processes based on hydrogen bond formation is that the complexes formed can be easily cleaved e.g. by addition of water or by increasing the temperature whereupon complexant is recycled. The structure and the physical properties of urea complexes with water, hydrogen peroxide, phenol, cresols, dihydroxybenzenes, naphthols and tetrabutylammonium acetate are reviewed. Physical properties of urea single crystals are also mentioned which can be applied in non-linear optics. The literature data on urea behaviour in complexed systems both calculated theoretically and determined experimentally are collected and discussed.


Wiadomości Chemiczne, 2000, 54, 971.
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THE ROLE OF VAN DER WAALS COMPLEXES IN THE THERMAL ELECTRON CAPTURE PROCESSES IN THE GAS PHASE

Iwona Szamrej

Instytut Chemii , Akademia Podlaska, ul. 3 Maja 54, 08-110 Siedlce


In this review electron attachment processes in the gas phase are described. Electron attachment occurs when electron in collision with atom or molecule forms negative ion. Usually it is a simple two-body collision but in some particular cases very interested, especially for chemists, multi-body processes occur. The results and the discussion on these multi-body thermal electron capture reactions for three groups of compounds, inorganic hydrides, halocarbons and oxygen containing molecules, are presented. It is demonstrated that in all these compounds the electron attachment by van der Waals complexes is much more efficient than by individual molecules and goes through different mechanisms.


Wiadomości Chemiczne, 2000, 54, 991.
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SYNTHESIS OF ORGANIC PEROXY COMPOUNDS

Stefan Baj, Małgorzata Dawid

Instytut Chemii i Technologii Organicznej, Politechnika Śląska, ul. Krzywoustego 4, 44-100 Gliwice


Organic peroxides are an interesting group of organic compounds. The O-O bonds in their structure warrant their properties determining the range of their application. The chemistry of peroxy substances is a branch of knowledge which is continuously developing. In the course of recent years much progress has been achieved both in the field of synthesizing new peroxides systems and in applaying them, particularly concerning their biological transformations.

A peroxide bond displays a low dissociation energy (20-50 kcal/mol) and that is why they are rather unstable. The reactions of peroxy substances may be divided into homolytic (radical) and heterolytic (ionic) ones. The most popular reaction of the monomolecular homolytic decomposition of the peroxide bond into radicals, occuring under the influence of temperature or radiation, is typical for all classes of peroxy substances and has found practical application. Theretically possible is also a molecular heterolytic decomposition of the peroxide bond into ions. Such a decomposition cannot compete, however, with the homolitic one and is required only in few specific cases. The O-O bond can also undergo transfomations in result of reactions with other substances. Also these reactions may be divided into two fundamental types. Some peroxy substances, e.g. hydroperoxides and peroxy acids, are electron donors and may occur in the reactions as nucleophiles. On the other hand, peroxy substances display the properties of "soft electrophiles" reacting with nucleophilic reagents. The result of such a reaction is a heterolytic decomposition of the peroxide bond. This ambivalent feature of peroxy substances becomes most visible in the natural process of peroxy acids in a basic medium, in which the RCO3- ion plays the role of a nucleophile attacking the non ionized particle (the electrophile).

In recent years it has been more and more often stipulated that the reactions of peroxides with nucleophiles run in compliance with the mechanism of the electron transfer (SET) from the nucleophile particle to the oxygen atom of the peroxy bond, in the result of which radicals and radical ions are formed in the course of this reaction. It ought to be stressed that it is extremely difficult to determine the mechanisms of many reactions of peroxy substances explicitly, becouse these types of reactions (SN2, SET) may take place simultaneously and in most cases lesd to the formation of some products.


Wiadomości Chemiczne, 2000, 54, 1023.
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THE ALKALI METALS OF NEGATIVE OXIDATION NUMBER

Andrzej Misiołek* , Violetta Łysiak**, Krystyna Jarzembek**

*Zakład Ochrony Środowiska , Wyższa Szkoła Ekonomii i Administracji,
ul. A. Frycza-Modrzewskiego 12 , 41-907 Bytom
**Instytut Chemii Uniwersytetu Śląskiego , ul. Szkolna 9 , 41-006 Katowice


It is usually believed that alkali metals can only take positive oxidation number. In 50s and 60s the solutions of alkali metals in amines and liquid ammonia have been investigated, and the presence of solvated electrons (paramagnetic individuals) and of some diamagnetic individuals in these solutions was found [2, 5].

In 70s macrocycles have been used for the solubilization of alkali metals. The concentration of metals in solutions considerably increases in the presence of these compounds, which makes the solutions of alkali metals an interesting object for chemical and in particular physico-chemical investigations. These indicated that it is the alkali metal anion that is responsible for diamagnetism of the samples [8-14].

Until now a variety of methods have been developed which aimed at synthesis of the compounds containing the alkali metal anion found in solutions or as crystals (ionic crystals) [10, 19, 23, 38]. The physical and chemical properties of such compounds and their use in synthesis have been investigated [10, 49, 52, 54, 56].


Wiadomości Chemiczne, 2000, 54, 1063.
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BIOLOGICALLY ACTIVE BISPHOSPHONATES. STRUCTURE, SYNTHESIS, PROPERTIES AND ACTION

Ewa Bałczewska*, Piotr Bałczewski**

*Zakład Chorób Błony Śluzowej, Jamy Ustnej i Przyzębia, Instytut Stomatologii AM, ul. Pomorska 251,
92-213 Łódź; fax: (42) 678 93 68
**Centrum Badań Molekularnych i Makromolekularnych PAN, ul. Sienkiewicza 112,
90-363 Łódź, E-MAIL: pbalczew@bilbo.cbmm.lodz.pl; fax: (42) 684 71 26


The increasing interest in design and application of biologically active bisphosphonates and the lack of the relevant treatment of this subject in Polish language with emphasis of its chemical aspects, induced us, to review the literature up to April 2000 using Medline and Beilstein Cross Fire databases.

Bisphosphonates are chemically and enzymatically stable analogs of physiological pyrophosphates which constitute natural inhibitors of mineralisation. Although first bisphosphonates were synthesized in the middle of XIX century, the concept of their use as inhibitors of bone resorption appeared in 1968. One group of biologically active bisphosphonates, which included the earliest bisphosphonates, constituted methylenebisphosphonates bearing simple 1-alkyl; 1,1-dihalo, 1-thiophenyl and/or 1-hydroxy substituents at the P-C-P grouping with a specific affinity to the bone tissue (etidronate, clodronate, tiludronate). The ability of bisphosphonates to bind to crystals of hydroxyapatites and to prevent both crystal growth and dissolution was enhanced when 1-chlorine atom (as in clodronate) was replaced by 1-hydroxyl group (as in etidronate). Newer bisphosphonates having a basic primary nitrogen atom in an alkyl chain (as in pamidronate and alendronate) and the recent ones containing a tertiary nitrogen (as in ibandronate and olpadronate) or a nitrogen atom within the heterocyclic ring (as in risedronate and zoledronate) are much more potent anti-resorptive compounds. The potency to inhibit bone resorption in rats increases from 1 to 10 000 in the sequence etidronate< clodronate, tiludronate< pamidronate, neridronate< alendronate, olpadronate< ibandronate, risendronate< zoledronate. Very small effective antiresorptive doses of the newest bisphosphonates clearly show that these bisphosphonates inhibit bone resorption by direct cellular effects on osteoclasts or by indirect effect through stimulation of osteoblasts to produce an osteoclast - inhibitory protein factor.

In this review historically first syntheses of bisphosphonates described by Menschutkin (1865) and von Bayer-Hofmann (1898) as well as representative syntheses of clodronate, tiludronate, pamidronate, alendronate and risedronate are presented.


Wiadomości Chemiczne, 2000, 54, 1075.
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OXYGENATED DERIVATIVES OF CHOLESTEROL. OCCURRENCE, BIOLOGICAL ACTIVITES, METHODS OF ANALYSIS

Danuta Bodzek, Beata Janoszka, Tomasz Wielkoszyński

Katedra i Zakład Chemii, Wydział Lekarski w Zabrzu,
Śląska Akademia Medyczna w Katowicach, ul. Jordana 19, 41-808 Zabrze.


The trends of cholesterol oxidation in living organisms and the main products of this process have been presented [1-7]. Biological activity of oxycholesterols have been characterised as well as their occurence in biological material [8-32].

A three-step analytical procedure of oxycholesterols determination has been suggested. A range and conditions for the following methods (Solid Phase Extraction, Thin Layer Chromatography, Gas Chromatography, High Performance Liquid Chromatography, Mass Spectrometry) application in oxycholesterols separation, identification and quantitative determination have been discussed [33-63].

Reagents most often used for oxycholesterol derivatization as well as reagents used for oxycholesterol visualization after the separation by TLC method have been presented. Some difficulties in analysing these compounds have been mentioned.


Wiadomości Chemiczne, 2000, 54, 1089.
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NOTATKI CHAOTYCZNE. XXXI. CHEMIA I MINERALOGIA W TWÓRCZOŚCI JULIUSZA SŁOWACKIEGO

Ignacy Z. Siemion

Wydział Chemii Uniwersytetu Wrocławskiego, ul. F. Joliot-Curie 14, 50-383 Wrocław



Wiadomości Chemiczne, 200, 54, 1109.
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