15 N– 13 C spin–spin coupling constants in some aniline derivatives

Abstract

Nitrogen–carbon spin–spin coupling constants in aniline- 15 N and some of its derivatives have been measured using 13 C Fourier transform nmr spectroscopy. Observed values of 1 J( 15 N, 13 C) in these aniline derivatives are dependent on the nature of the substituent as well as the solvent. Observed values of 1 J( 15 N, 13 C) in the amino fragment of a number of amine derivatives are linearly related to the corresponding 1 J( 15 N,H) values in these compounds. The 1 J( 15 N, 13 C) values in these compounds also appear to be related to the N(s)—C(s) bond order. Comparison of observed 1 J( 15 N, 13 C) values in a number of compounds with those calculated using INDO–MO theory indicate that 1 J( 15 N, 13 C) in aniline and its derivatives is negative, that is, 1 K(N,C) is positive. Observed and calculated 15 N– 13 C spin–spin coupling constants over two and three bonds are also presented.