Conformations of some saturated carbonyl compounds. Part I. Infrared spectra of methyl formate, acetate, propionate, and n-butyrate; [2H3]methyl propionate and [2H3]methyl n-butyrate

Abstract

I.r. spectra of methyl formate, acetate, propionate, n-butyrate; and [²H₃]methyl propionate and n-butyrate are reported. The effects of cooling solutions in carbon disulphide from 35 to –110°, and of solidification, on these spectra are interpreted in terms of conformational equilibria. One pair of conformers is suggested for methyl propionate for which the additional enthalpy (ΔH°) for the high energy form is 87 ± 19 cal mol^–1. Two pairs of conformers are suggested for methyl n-butyrate for which the additional enthalpies of the high-energy forms are 92 ± 27 and 440 ± 20 cal mol^–1. It was not possible to determine ΔS° from the data.