N-oxides and related compounds—XXXIX

Abstract I-Aminopyridinium cation in aqueous solution at high pH is in equilibrium with pyridine 1-imide (of pK 13·5) which slowly decomposes. N-Aminopyridinium cations and their acylated and sulphonylated derivatives readily undergo deuterium exchange at the 2- and 6-positions on base catalysis but are not susceptible to acid-catalysed deuteration. Nitration occurs at the amino group with the concomitant hydrolysis of an acyl or sulphonyl group.