The mechanism of the electrophilic substitution of heteroaromatic compounds. Part VI. The nitration of pyridines in the 3-position as free bases and as conjugate acids

Abstract

Kinetic studies of the nitration of 2,4,6-trimethylpyridine and 1,2,4,6-tetramethylpyridinium cation in sulphuric acid have shown that the former reacts as the conjugate acid. 2,4- and 2,6-Dimethoxypyridine are also mononitrated in the 3-position via the protonated species. The second nitration of the latter compound proceeds on the free base, as does the mononitration of 2,6-dichloropyridine. Attempts have been made to compare the reactivities of benzene, pyridine, and the pyridinium cation towards the nitronium ion.