The far infrared spectra of a number of aliphatic amines have been recorded as dilute solutions in cyclohexane. A characteristic band with center at 225 ± 10 cm−1 is present in the spectra of aliphatic primary amines with a primary α-carbon atom. On the basis of the deuterium shift this band is assigned to the amino torsion. The effects of branching at the α-carbon, coupling of methyl and amino torsions, and intramolecular association on the frequencies of NH2 torsions are discussed.
Stephen M. Craven and Freeman F. Bentley, "Far Infrared Group Frequencies. II. Primary Amines," Appl. Spectrosc. 26, 449-453 (1972)