C13 Nuclear magnetic resonance spectroscopy. IV. Aniline, N,N-dimethylaniline, and their methyl derivatives: Steric inhibition of conjugation

Abstract

The C13 nuclear magnetic resonance spectra of aniline, nine methylanilines, N,N-dimethylaniline and eight methyl-N,N-dimethylanilines have been obtained and analyzed. A detailed study of the influence of methyl substituents on ring carbon shieldings has been made, and estimates of the changes in charge distributions resulting from steric inhibition of conjugation derived from the results. Reasonably good agreement with other theoretical and experimental investigations of these effects has been found. The N-methyl carbon shieldings appear to be correlated with the base strengths of the amines.