Conformational studies of propenoyl chloride in liquid xenon from temperature dependent FT-IR spectra

Abstract

Variable temperature (−60 to −100°C) studies of the infrared spectra (3500 to 400 cm −1) of propenoyl chloride, CH 2CHCClO, dissolved in liquid xenon have been recorded. From these data the enthalpy difference has been determined to be 139 ± 8 cm −1 (397 ± 23 cal/mol) with the anti conformer (carbonyl bond trans to the carbon-carbon double bond) more stable than the syn form. From this ΔH value along with assigned torsional fundamentals and accompanying “hot bands” the potential function governing the conformational interchange has been calculated. Utilizing the new infrared data from the xenon solution, some new Raman data, and ab initio predictions from MP2/6–31G ∗ calculations a few reassignments of the fundamentals have been made. Ab initio calculations have been carried out with several different basis sets up to MP2/6–311G ∗∗ from which structural parameters and conformational stabilities have been determined. With all the basis sets the syn conformer is predicted to be the more stable conformer which is inconsistent with the experimental results. These results are compared to the corresponding quantities for some similar molecules.