CHAPTER 11 - AMINES, C=N, AND N=0 COMPOUNDS

Abstract

This chapter presents the general spectral features for amines and discusses other selected nitrogen compounds. The NH 2 group gives rise to absorption at 3550–3330 cm −1 (asymmetric stretch) and at 3450–3250 cm −1 (symmetric stretch). Most of the primary amines have an NH 2 deformation band at 1650–1590 cm −1 . In liquid aliphatic amines, the NH 2 wagging and twisting vibrations give rise to broad, strong, and multiple absorption bands at 850–750 cm −1 . The NH stretching vibration gives rise to a weak band at 3500–3300 cm −1 . In amines—as in alcohols—single bond frequencies are affected by branching at the α-carbon atom. Primary aromatic amines with the nitrogen directly on the ring absorb strongly at 1330–1260 cm −1 , 3 due to stretching of the phenyl carbon–nitrogen bond. Secondary aromatic amines absorb strongly at 1342–1320 and 1315–1250 cm −1 . Dimethyl anilines absorb strongly at 1380–1332 cm −1 . For all the tertiary anilines, the region is 1380–1265 cm −1 .