Kinetics and Mechanism of Bromination of 2-Pyridone and Related Derivatives in Aqueous Solution

Article abstract of DOI:10.1021/ja00379a016

The tautomeric system 2-pyridone <*> 2-hydroxypyridine (1a <*> 2a) reacts with aqueous bromine via the principal tautomer 1a at pH < 6 and via the conjugate anion at pH > 6.Attack upon 1a occurs preferentially at the 3 position, whereas reaction upon the anion probably involves major attack at the 5 position.The facile dibromination of 2-pyridone results from the comparable reactivity of the monobromopyridones at pH <1 or pH >4.These conclusions are based upon kinetic and product studies of the bromination of 1a and various derivatives in aqueous solutions at pH 0-8.With respect to their reactivity toward bromine the pyridones behave as substituted phenoxide ions.