Hydrogen bonding and vapor pressure isotope effect of ethanethiol

Abstract

The vapor pressure ratios of ethanethiol and ethanethiol-d1 between 223 and 323 K can be represented by the relation[Formula: see text]The PD/PH vs. T curve increases initially and reaches a flat maximum at 293 K; at higher temperatures there is an apparent decrease. This behavior can be explained by the superposition of predominantly the normal effect of the intermolecular vibrations and the SH and SD torsion vibrations, and the inverse effect of the SH and SD stretching vibrations. Contrary to the value of 0.91 reported previously, PD/PH values of 1.002 to 1.008 confirm that for weakly hydrogen-bonded substances and their deuterium-bonded analogues a negligibly normal or a slightly inverse vapor pressure isotope effect should be observed.