The mechanism of the electrophilic substitution of heteroaromatic compounds. Part XI. Acid-catalysed hydrogen exchange of α- and γ-pyridones and γ-quinolone

Abstract

2- and 4-Pyridone, and certain C- and N-methyl-derivatives are shown to undergo acid-catalysed hydrogen exchange at the 3- and 5-positions as the neutral species from pD 4 to H₀–10. 4-Quinoline at higher acidities undergoes exchange as the conjugate acid successively in the 3-, 6-, 8-, and 5-positions; at lower acidities it exchanges as the neutral species at the 3-position. Exchange rates for exchange in the o- and p-positions of phenol and the phenolate ion are reported. The preceding, and other, rates are compared under standard conditions, and partial rate factors for the substitution of CH in benzenoid compounds by NH⁺ are presented.