Heteroaromatic reactivity. Part II. The kinetics of nitration of pyridine 1-oxide, 2,6-lutidine 1-oxide, and isoquinoline 2-oxide

Abstract

By studying the acidity dependence of the rate of nitration in sulphuric acid (76·4–83·1%), and by comparison with 2-methoxyisoquinolinium cation, it has been shown that nitration of isoquinoline 2-oxide goes through the cation. By similar methods, 2,6-lutidine 1-oxide has been shown to be nitrated through the free base (78·2–97·8% sulphuric acid), as is pyridine 1-oxide (87·9% sulphuric acid). Arrhenius parameters have been obtained for these three substrates, and partial rate factors evaluated. In the case of pyridine 1-oxide the latter were compared with the predictions of Hückel molecular orbital theory.