Vibrational spectra and assignments of tetrafluorooxirane- 16O and - 18O

Abstract

Infrared and Raman spectra are reported for tetrafluorooxirane and its 18O modification. From these spectra and previously reported microwave spectra, a complete assignment of vibrational fundamentals is obtained. For the 16O species the frequencies in cm −1 are ( a 1) 1610, 1161, 792, 502, 323; ( a 2) 1242, 515, 234; ( b 1) 1286, 776, 696, 528; ( b 2) 1130, 558, 186. For the 18O species they are: ( a 1) 1611, 1136, 789, 494, 321; ( a 2) 1242, 515, 234; ( b 1) 1284, 777, 679, 516; ( b 2) 1129, 539, 185. Frequency shifts with 18O substitution show that ν 2 is symmetric CO stretching, that ν 11 and ν 12 contain antisymmetric CO stretching, and that ν 14 is flapping of the COC part with respect to the F 2CCF 2 part. Since ν 1 is independent of 18O substitution, this mode must be largely CC stretching mixed with symmetric CF 2 stretching. This finding corroborates a similar result for trans-2,3-difluorooxirane and negates the previous ascription of “ring breathing” to this mode.