Vibrational spectrum and molecular structure of methyl pyruvate

Abstract

The infrared spectrum of methyl pyruvate in the liquid phase in the vapour phase, in solution, and as a glassy and crystalline solid has been obtained from 4000 to 200 cm-1, together with the Raman spectrum of the liquid. The data are consistent with the assumption of a planar pseudo-trans isomer in the crystalline state, and a mixture of this isomer with a less stable planar pseudo-cis isomer in the other phases investigated. The energy difference between the two isomers in the liquid state was found to be c. 650 cal mol-1. A complete assignment, with the exception of the torsional modes, has been made for both rotational isomers.