Amine C-N Stretching Vibrations

The C-N stretching absorption of primary aliphatic amines is weak and occurs in the region 1090-1020cm (9.17-9.77pm). Secondary aliphatic amines have two bands of medium intensity at 1190-1170cm (8.40-8.55 pm) and 1145-1130cm (8.73-8.85pm). 

For aromatic and unsaturated amines =C-N, two bands are observed at 1360-1250 cm (7.36-8.00 pm) and 1280-1180 cm (7.81-8.48 pm) due to conjugation of the electron pair of the nitrogen with the ring imparting double-bond character to the C-N bond, primary and secondary aromatic amines absorbing strongly in the first region. The C-N band for tertiary aromatic amines is found at 1380-1265 cm (7.25-7.91 pm). 

Itnines with aliphatic groups attached to the nitrogen atom have a band near 1670 cm (5.99 pm), with aromatic groups attached, this band is near 1640cm (6.10pm) and, with extended conjugated groups, it is near 1620 cm (6.17 pm). 

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