Spectroscopic and thermodynamic study of the conformational properties and torsional potential functions of methacryloyl fluoride

Abstract

The infrared (3500–40 cm−1) and Raman (3500–10 cm−1) spectra have been recorded for the gaseous and solid phases of methacryloyl fluoride. Additionally, the Raman spectrum of the liquid has been recorded and qualitative depolarization values have been obtained. The asymmetric potential function for internal rotation of the O = C–F top has been determined from far infrared data, and the following potential constants have been evaluated: V1 = 257±4; V2 = 1582±6; and V3 = 173±3 cm−1. From these data, the s-trans conformer was determined to be the predominant rotamer at ambient temperature with the other conformer being the s-cis; the enthalpy difference between the s-trans and s-cis conformers is 430 cm−1 (1230 cal/mol). This value compares well with the value of 444 cm−1 (1270 cal/mol) obtained for the liquid from a variable temperature study of the Raman spectrum. The methyl torsional barrier was also calculated from the far infrared data to be 1.77 kcal/mol. A vibrational assignment and values for the thermodynamic functions of gaseous methacryloyl fluoride are presented.