Infra-Red and Raman Spectra of Polyatomic Molecules XIII. Nitromethane

The infra-red spectrum of gaseous nitromethane has been studied over the wave-length range from 3 to 25 μ. The Raman work of Pendl, Reitz and Sabathy has been checked. These data together with a partial normal coordinate treatment enable us to make an assignment of the observed lines and bands which accounts for all the fundamental frequencies except the torsion around the C–N bond. The fundamental frequencies for the gas are 476, 599, 647, 921, 1097, 1153, 1384, 1413, 1449, 1488, 1582, 2965, 3048 (2). No decision regarding the potential barrier restricting the internal rotation of the methyl group can be made until at least one thermo dynamic quantity has been measured. The present results are compatible with the usual structure CH3NO2.