Kinetics and mechanism of iodination of 8-hydroxyquinoline

Abstract

Kinetic measurements on the reaction of iodine with 8-hydroxyquinoline (oxine) are consistent with a reaction between molecular iodine and oxinate anion, through a cyclohexadienone intermediate, i.e. a mechanism similar to that observed for iodination of phenol, but different from that proposed for bromination of oxine. The enthalpy of activation is also very similar to that observed for phenol. Catalysis by acetate ion is observed, and both the catalytic rate coefficient and that for the ‘uncatalysed’ reaction are about 300 times those for phenol at 25°.