High-Resolution FTIR Spectrum of Jet-Cooled CH₃CHF₂

Abstract

The mid-IR spectrum of HFC-152a, CH 3 CHF 2 , has been recorded using a supersonic jet-FTIR spectrometer system, at high and low resolution. Molecular constants have been obtained from a vibration-rotation analysis of the A-type band ν 5 (1413 cm -1 ) and the B-type band ν 16 (941 cm -1 ). The resultant constants have been used to simulate band profiles, from which the rotational temperature in the jet has been estimated to be 50 K. The vibrational assignment of CH 3 CHF 2 has been revised using the low-resolution jet spectrum and Raman and far-infrared spectra recorded at room temperature.

Predicting the vibrational spectra of some simple fluorocarbons by direct scaling of primitive valence force constants

“…tal gas-phase vibrational frequencies : fluoromethane, 18 trifluoromethane, 19 carbon tetrafluoride, 20 fluoroethylene, 21 1,1-difluoroethane, 14 1,1,1-trifluoroethane, 40 1,1,1,2-tetrafluoroethane, 15 perfluoroethane, 4 1 3,3,3-trifluoro-2-m ethyl-propene, 23 2-fluoropropane, 24 2,2-difluoropropane, 25 and 1,1,1,2,3,3,3-heptafluoropropane. 26 The training set was chosen with some care.…”

“…12,13 In this work we look at the vibrational frequencies of all of the fluoromethanes, fluoroethylenes, fluoroethanes, and monofluoropropenes examined in the previous two studies 10,11 using the new primitive SQM scheme. 9 There have been experimental determinations-mainly by jet-cooled FTIR spectroscopy-of the vibrational spectra of several of the fluorocarbons examined here during the last few years, including 1,1-difluoroethane 14 and 1,1,1,2-tetrafluoroethane, 15 and we use these, together with other experimental data, to derive a set of scaling factors for use with simple fluorocarbons. We then use these scaling factors to predict the fundamental frequencies and IR intensities of the remaining fluorocarbons in our set, 10,11 comparing our predicted frequencies with experimental values where available.…”

Mechanical and thermal properties of perfluoroalkyl ethyl methacrylate–methyl methacrylate statistical copolymers synthesized in supercritical carbon dioxide

“…2. The peak at 1726 cm À1 in the spectrum signifies the C5 5O stretching vibration relating to the methacrylate segments [45] and the peak at 1142 cm À1 corresponded to the CF 2 stretching belonging to the fluoro methacrylate segments [46]. X-ray diffraction (XRD) measurements give the percentage of the amorphous or the crystalline regions.…”

Ro-vibrational analysis of the ν9 and ν16 bands of R152a

“…Spectroscopic studies of R152a to date include the measurement of infrared absorption cross-sections [4] microwave spectroscopy supported by ab initio calculations to determine molecular structure and the barrier to internal rotation [5] and photochemical reaction studies [6]. Vibrational assignments for this molecule, supported by ab initio calculations, are summarized in the works of McNaughton and Evans [7] and Appadoo et al [8].…”

“…High-resolution infrared spectroscopic studies have been restricted to the analysis of a limited number of strong bands where the spectra have been simplified by free jet supersonic expansion [7] or enclosive flow cooling techniques [8]. In the latter study by Appadoo et al the a/c-type band, m 4 (1456.9 cm À1 ) was assigned and fitted in a treatment which accounted for Coriolis resonance with the dark state, t 13 = 1 at 1451 cm À1 .…”