Wydział Chemii

Aleksander Filarowski

Poul Erik Hansen

2013

Zeitschrift für Physikalische Chemie - International Journal of Research in Physical Chemistry and Chemical Physics

227

917-927

10.1524/zpch.2013.0378

Naukowa

Angielski

Artykuł

An analysis is presented of secondary deuterium isotope effects on ¹⁵N and ¹³C chemical shifts of the methylamine Schiff base of 4,6-dimethoxysalicylaldehyde. It is shown that for this compound existing as an equilibrium between an OH and a NH-form, the secondary isotope effects depend on the OH/NH ratio giving a function with a maximum and a minimum.

Secondary deuterium isotope effects on ¹³C and ¹⁵N chemical shifts are compared in a broader range of compounds and the above trend is confirmed. Changes in the dielectric constants of the medium with temperature are found to be rather unimportant for the change in equilibrium. Equilibrium isotope effects on chemical shifts are shown to be important. The magnitudes of the isotope effects are correlated both to intrinsic and equilibrium isotope effects. The latter correlate to the shape of the two-potential well, the energy difference and the difference in chemical shifts of the two tautomers.

Secondary Deuterium Isotope Effects, Chemical Shifts, Schiff bases, DFT calculation, intramolecular hydrogen-bonding

http://dx.doi.org/10.1524/zpch.2013.0378