Raman and infrared spectra, vibrational assignment and ab initio calculations of trans‐2‐methyl‐2‐butenenitrile

Abstract

AbstractThe Raman (3100‐10 cm−1) and infrared (3100‐400 cm−1) spectra of trans‐2‐methyl‐2‐butenenitrile [trans‐CH3CH =C(CH3)CN] were recorded for the gas, liquid and solid phases. Additionally, the far‐infrared (370‐60 cm−1) spectrum of the gas was recorded. These data were interpreted on the basis that only the trans (two methyl groups trans to each other) isomer is present on purification. Only one of the methyl torsional fundamentals was observed and it corresponds to the methyl group on the same carbon atom as the cyano group. The experimental barrier to internal rotation is 610 ± 30 cm−1 (1.74 ± 0.09 kcal mol−1). The structure, infrared intensities, Raman activities, depolarization ratios and vibrational wavenumbers were determined from ab initio calculations using the RHF/3‐21G, RHF/6‐31G* and MP2/6‐31G* basis sets. These results are compared with those obtained for some related molecules.