Hydrogen bonds of thioacetic and chlorothioacetic acids with various electron donors

Abstract

Hydrogen bonds in which thiocarboxylic acids participate have received little quantitative study [i]. In [2, 3], in an investigation of the association of certain thiocarboxylic acids with electron donors by the methods of NMR and IR spectroscopy, the frequencies of the stretching vibrations and the chemical shifts of the protons of the SH groups were measured, but the energies of the hydrogen bonds were not calculated. Only in [4] was it shown that thioacetic acid forms stronger bonds with triethylamine than does propanethiol. This result is in qualitative agreement with the fact that thiocarboxylic acids are characterized by greater proton-donor capacity than mercaptoalcohols; however, from the quantitative standpoint this cannot be considered reliable, since in a calculation of the strength of the hydrogen bonds according to the data of the UV spectra, processes of protonation of the amide that follow the formation of hydrogen bonds were not considered.