Importance of repulsion of lone electron pairs in the enhanced reactivity of 1,8-naphthyridine and the large α-effect of hydrazine in the aminolyses of p-toluenesulfonyl chloride

The rates of aminolyses of p-toluenesulfonyl chloride with primary and tertiary amines have been determined both in acetonitrile and in ethanol. The Brönsted plots of log k rel again pK a′ values of amines (except hydrazine and 1,8-naphthyridine in acetonitrile) gave a good correlation when the aminolyses were carried out in acetonitrile. In ethanol, however, although Brönsted plots with all tertiary amines show a good correlation, less basic hydrazine shows a higher reactivity than n-butylamine. The abnormal rate enhancement found with hydrazine is undoubtedly due to the α-effect, while that with 1,8-naphthyridine in acetonitrile is considered to be due to the repulsion of two lone electron pairs on the two nitrogen atoms in 1,8-naphthyridine