Low frequency vibrational spectra and internal rotation of 2hyphen;chlorobutahyphen;1,3hyphen;diene, propenoyl fluoride, and propenoyl chloride

摘要

The infrared and Raman spectra of gaseous 2hyphen;chlorobutahyphen;1,3hyphen;diene, propenoyl fluoride, and propenoyl chloride have been recorded below 300 cmminus;1. It was observed that the low frequency spectra of these three molecules were quite similar. The infrared spectrum of 2hyphen;chlorobutahyphen;1,3hyphen;diene exhibited a series of sharp torsional transitions whereas in the Raman spectrum aBhyphen;type band was observed. These torsional frequencies have been assigned to theshyphen;transconformer and no evidence for a higher energy conformer was observed. In the infrared and Raman spectra of the propenoyl halides, bands assigned to the torsional series of both conformers have been observed. The analyses of these spectra were simplified by comparison with that of the 2hyphen;chlorobutahyphen;1,3hyphen;diene. Asymmetric potential functions and values for Dgr;Hfor propenoyl fluoride and propenoyl chloride were calculated. The enthalpy differences of 36 and 215 cmminus;1between the lowest energy levels of theshyphen;transandshyphen;ciswells for the propenoyl fluoride and chloride, respectively, were obtained.