Nucleophilic substitution reaction of p-nitrophenyl acetate (PNPA), p-nitrophenyldiphenyl phosphinate, and pesticide parathion with different α-nucleophiles [I] have been studied at 27 °C in different pH in the presence of a novel cationic surfactant. The kinetic study was performed spectrophotometrically under pseudo-first order conditions with the α-nucleophile in excess. The pKa of nucleophiles have also been determined by kinetic method. In the presence of surfactant, the rate constant increased with increasing surfactant concentration up to a limiting value. This behavior has been analyzed in quantitative terms on the basis of pseudo-phase model of micellar catalysis. Finally the nucleophilic reactivity of hydroxamate ions has been compared with other α-nucleophiles, like oxime, hydroxybenzotriazole, and 2-iodosobenzoic acid (IBA). The order of cleavage of electrophilic centers, that is, CO, PO, and PS have also been discussed. Copyright © 2008 John Wiley & Sons, Ltd.