The vibrational spectra of compounds containing the dimethylamino-group. Part II. p-NN-dimethylaminobenzonitrile and the N-methyltoluidines

Abstract

The i.r. and Raman spectra of p-chlorobenzonitrile and p-NN-dimethylaminobenzonitrile have been recorded in the range 4000–10 cm^–1. The fundamental vibrational frequencies of these systems have been computed. On the basis of these calculations and by analogy with related molecules the observed spectral bands have been assigned. It is shown that several modes exist which might be characteristic of the dimethylamino-group and that considerable mixing occurs in some instances between the modes of the ring and the amino-group. Some tentative conclusions concerning the structure of the C₆–NC₂ skeleton are made. A survey of the spectra of the N-methyl-toluidines and -anilines has been made which supports the identification of the characteristic bands of the aromatic –NMe₂ and aromatic –NHMe entities.