Deuterium isotope effect in the IR spectra of some pyridine trifluoroacetates in benzene

Abstract

The infrared spectra of 10 substituted pyridines with trifluoroacetic acid-d 1 were examined in dry benzene and benzene-d 6 with respect to the mass effect on the AH stretching vibration. The isotopic frequency ratio of the gravity centres, V̄ o H / V̄ o D , varies between 1.04 and 1.19. The isotopic frequency ratio, together with the previously described solvent effect on the chemical shift of hydrogen bonded protons, possibly indicates an expansion of the distance on deuterium replacement.