Conformational studies of propenoyl fluoride in liquid xenon from temperature dependent FTIR spectra

Abstract

-Variable temperature (-60°C to -100°C) infrared spectra (3500–400 cm -1) of propenoyl fluoride, CH2CHCFO, dissolved in liquid xenon have been recorded. From these data the 2 enthalpy difference has been determined to be 113±15 cm-1 (322±42 cal mol-1) with the anti conformer (carbonyl bond trans to the carbon-carbon double bond) more stable than the syn form. From this Δ H value along with assigned torsional fundamentals for both conformers and accompanying ‘hot bands’ the potential function governing the conformational interchange has been calculated. Utilizing the infrared data from the xenon solution, some new Raman data, and ab initio frequency 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 MP2/6-311++G** from which structural parameters and conformational stabilities have been determined. With all the basis sets, the anti conformer is predicted to be the more stable conformer, which is in agreement with the experimental results. These spectroscopic and theoretical results are compared with the corresponding quantities for some similar molecules.