Kinetics, stoichiometry and mechanism in the bromination of aromatic heterocycles. IV. Aqueous bromination of Imidazo[1,2-a]pyridine

Abstract

The reaction of imidazo[l,2-a]pyridine with bromine has been studied in dilute acidic aqueous solution at 25ºC. The bimolecular rate coefficient for attack by Br₂ on the molecular substrate at the 3-position is found to be Kº_bi = 1.30(± 0.05) x 10⁹ dm³ mol^-l s^-l We find pK.(imidazo[l,2-a]pyridine-H⁺, aq., 25ºC) = 6.65 and pK,(3-bromoimidazo[l,2-alpyridine-H⁺, aq.,25ºC) = 4.95. The latter compound reacts with bromine in aqueous acetate buffer at pH4.