Cetyl pyridinium chloride catalysed reaction of acridine yellow with acidic chloramine-T

Abstract

The kinetics and mechanism of the uncatalyzed and cetyl pyridinium chloride (CPC) catalyzed oxidation of acridine yellow (3,6-diamino-2,7-dimethyl acridine hydrochloride) dye by chloramine-T in acidic media has been studied spectrophotometrically. With excess concentrations of other reactants, the reaction rate follows pseudo-first order kinetics with respect to acridine yellow. The uncatalyzed reaction has fractional order dependence on chloramine-T as well as on H + concentration. The catalyzed reaction follows fractional order kinetics in [CPC]. The cetyl pyridinium chloride, a cationic surfactant, catalysed the reaction even before its critical micelle concentration. This premicellar kinetics has been rationalized in the light of Piszkiewicz positive co-operativity model. The positive co-operativity index n = 1.95 has also been computed. The spectral shifts are the evidences of dye-surfactant and dye-surfactant-oxidant interactions. Variations of ionic strength has no influence on the reaction rate suggesting that neutral charged species are involved in the rate-determining step. Increase in the addition of p-toluenesulfonamide resulted in decrease in rate constant values. The basic stoichiometric equation is as follows ; AY + + ArSO 2 NHCl + H 2 O = P + + ArSO 2 NH 2 + CH 3 CH 2 OH + CH 3 CN + 2HCl, whene P + = 7-aminoquinoline-2,3-dicarboxylic acid. On the basis of the product analysis pertinent mechanisms are proposed.