Vibrational spectra and structure of nitrogen containing molecules—I. Formaldehyde dimethylhydrazone

Abstract

The i.r. spectrum of formaldehyde dimethylhydrazone, (CH 3) 2NNCH 2, has been studied from 3400 to 200 cm −1 in the gaseous state and between 3400 and 140 cm −1 at liquid nitrogen temperatures. A comparison of the vibrational spectra in the solid and fluid states indicates the molecule exists in only one conformer in all three physical states. The Raman spectra of the gas, liquid and solid have also been recorded and depolarization values measured. In view of the number of polarized Raman lines, the vibrational spectra have been interpreted in terms of C 1 symmetry. A vibrational assignment is presented based upon the observed band positions, intensities and group frequency considerations. Whereas the methyl torsional modes were assigned to bands at 271 and 241 cm −1 in the absorption spectrum of solid (CH 3) 2NNCH 2, the counterparts to these transitions were centered at 258 and 239 cm −1 in the Raman effect. A similar difference in the i.r. and Raman frequencies of other fundamentals was ago observed and these splittings have been attributed to the correlation field. A low frequency i.r. spectrum of (CH 3) 2NNCH 2 isolated in an argon matrix was also studied and is compared to the spectra obtained for the crystalline state.