Correlation of N.M.R. chemical shifts of N-methyl protons of substituted dimethylanilines with Hammett substituent constants

Abstract

The proton magnetic resonance chemical shifts of N-methyl protons in para-substituted NN-dimethylanilines have been correlated with the Hammett ø- value of the para substituent. The correlation yields ø- values of 1.57 ± 0.09 and 0.85 ± 0.09 for the para nitroso and para 4'-dimethylaminobenzoyl substituents, respectively. The solvent shift of the N-methyl protons between chloroform and benzene solutions also fits a linear correlation with Hammett ø-, and yields ø- = 1.52 ± 0.11 for the para-nitroso substituent.