Conformations of some αβ-unsaturated carbonyl compounds. Part I. Infrared spectra of acraldehyde, crotonaldehyde, methyl vinyl ketone, and ethylideneacetone

TLDR: In this article, the infrared spectra of acraldehyde, crotonaldehyde, methyl vinyl ketone, and ethylideneacetone in solution and vapour states are reported, and band intensity measurements at temperatures between -110° and 200° are interpreted in terms of conformational equilibrium between the s-trans and non-trans forms of the ketones.

Abstract: Infrared spectra of acraldehyde, crotonaldehyde, methyl vinyl ketone, and ethylideneacetone in solution and vapour states are reported. Band intensity measurements at temperatures between –110° and 200° are interpreted in terms of conformational equilibrium between the s-trans and non-trans forms of the ketones. The additional enthalpy (ΔH) of the non-trans forms are: [graphic omitted] No evidence is found for more than one form of the aldehydes and the rotational structure of vibrational bands of both acraldehyde and crotonaldehyde suggest these exist in the s-trans conformation. Vibrational assignments are provided for the various conformations detected in these compounds.