Microwave and infra-red spectra and conformation of methyl trifluoroacetate

Abstract

The microwave spectrum, between 14 000 and 40 000 MHz, and the infra-red spectrum, between 4000 and 10 cm–1, have been obtained for methyl trifluoroacetate. The molecular conformation has been found to be planar or near-planar cis(i.e., methyl group cis to the carbonyl group). The dipole moment has been measured at 296 K in benzene solution and found to be 2.70 ± 0.15 D. Some of the infra-red absorption bands have been reassigned to group vibrations, and the potential barriers hindering internal rotation about the CF3—C and C(O)—O bonds are estimated from the torsional frequencies of the vapour to be 1.93 ± 0.77 kJ mol–1 and 47.7 ± 2.9 kJ mol–1 respectively.