Wydział Chemii

Sergey I. Vdovenko

Igor I. Gerus

Magdalena Pagacz-Kostrzewa

Maria Wierzejewska

2022

Journal of Molecular Structure

1255

132417/1-132417/10

10.1016/j.molstruc.2022.132417

Naukowa

Angielski

Artykuł

Spatial and electronic structure of possible isomers/conformers of three α-substituted β-ethoxyvinyl trifluoromethyl ketones with general formula F₃CCO–CR=CH–OC₂H₅, where R = H (I), R=F (II), and R = CH₃, (III), their ability to form H-bonds with two secondary amines, namely, diethyl amine (1) and bis(methoxyethyl)amine (2) have been studied. It was shown that all studied α-substituted enones are E-isomers forming predominantly three conformers, viz E-s-E-s-E-trans, E-s-Z-s-E-trans, and E-s-Z-s-E-gosh, percentage of separate conformer depending not only on environment but also on steric and/or special (repulsion) interaction between α-substituent and trifluorocarbonyl group. Hydrogen bonding ability evaluated in thermodynamic scale of hydrogen bond basicity revealed that pK_HB values of each conformer strongly depends on steric and/or effective charge change on carbonyl oxygen due to influence of α-substituent. Formation of H-bonded ternary complex between enone conformer and secondary amine changes electron density distribution in conformer conjugated chain, reducing positive charge on C_β and thus changing conformer electrophilicity. On the other hand cooperativity effect in amine dimer increases net charge on amine nitrogen thus enhancing amine nucleophilicity.

Conformers, α-substituted β-ethoxyvinyl trifluoromethyl ketones, Secondary amines, Hydrogen bond, Cooperativity effect, Electrophilicity, Nucleophilicity

http://dx.doi.org/10.1016/j.molstruc.2022.132417

http://www.elsevier.com