Oxidation of 2-hydroxynaphthaldehyde by alkaline N-bromosuccinimide - A kinetic and mechanistic study

The kinetics of the oxidation of 2-hydroxynaphthaldehyde (2-HNA) by N-bromosuccinimide (NBS) in aqueous alkaline medium at a constant ionic strength of 0.60 mol dm(-3) was studied titrimetrically. The reaction is of first order in [NBS] and of fractional order in both [2-HNA] and [alkali]. Addition of products has no significant effect on the reaction rate. However, increasing ionic strength and decreasing dielectric constant of the medium increases the rate. The oxidation process in alkaline medium has been shown to proceed via the formation of a complex between the active species of the oxidant and the substrate followed by the decomposition of the complex in a slow rate determining step to yield the product. Some reaction constants involved in the mechanism were determined. The calculated and observed rate constants agree excellently. The activation parameters were computed with respect to the slow step of the mechanism.