Intramolecular hydrogen bonds formed by primary aromatic amines. The N-H and N-D stretching frequencies of mono- and di-deuterated amines

Abstract

The N-H and N-D stretching frequencies of a number of deuterated, intramolecularly hydrogen-bonded amines have been examined. For the mono-deuterated amines, these bands are interpreted on the basis of cis-trans isomerism of the NHD group. The relative shifts of the N–H and N–D stretching bands are discussed in terms of the strength of the intramolecular hydrogen and deuterium bonds. A new method for the investigation of the tautomeric behaviour of primary amino groups is presented. By this method it is shown that 4',5-dimethyl-2-aminoazobenzene exhibits rotational isomerism in solution.