Titrations in non-aqueous media. Part III. Basicity order of aniline, N-Alkyl- and N-aryl-substituted anilines and pyridine in nitrobenzene solvent

Abstract

The relative basicity order of ammonia, pyridine, aniline and N-methyl-, N,N-dimethyl-, N-ethyl-, N,N-diethyl-, N-aryl- and N,N-diaryl-substituted anilines have been determined potentiometrically with perchloric acid in nitrobenzene solvent and found to be NH₃ > Py > PhNEt₂ > PhNMe₂ > PhNHEt > PhNHMe > PhNH₂ > Ph₂NH > Ph₃N. This order in general conflicts with the results observed by other workers in either the gas phase or in the condensed phase. N-Alkyl substitution increases the basicity of the aniline, and N-aryl substitution decreases its basicity. Moreover, the number and size of the substituent influence the basicity of aniline. N-Ethyl-substituted anilines are more basic than the corresponding N-methyl-substituted anilines. The position of pyridine in the order is surprising and difficult to interpret.