Studies on the reaction kinetics and the mechanism of hydrolysis of bis(4-nitrophenyl)phosphate (BNPP) by hydroxamic acid complexes containing benzo-15-crown-5

Abstract

A hydroxamic acid (HL) containing benzo-15-crown-5 and their copper(II), zinc(II), cobalt(II) and manganese(II) complexes have been synthesized and studied as catalysts for the cleavage of bis(4-nitrophenyl)phosphate (BNPP). The catalytic properties of these complexes and the kinetics and mechanism of BNPP hydrolysis have been investigated. The kinetic mathematical model of BNPP cleavage catalyzed by these complexes has been proposed. The effects of reaction temperature and metal ion in the complexes on the rate of BNPP catalytic hydrolysis have been discussed. The results show that the hydroxamic acid complexes containing benzo-15-crown-5 exhibit high activity in the BNPP catalyzed hydrolysis; the pseudo-first-order-rate constants of BNPP hydrolysis catalyzed by the complexes increase along with the increases of pH of the buffer solution from 7.50 to 9.50; the activity of different metal ions decreases in the order: Co2+ > Cu2+ > Zn2+ > Mn2+; the pseudo-first-order-rate constants of BNPP hydrolysis catalyzed by the complexes is 2.24 × 105 ~ 3.24 × 105 times as large as that of spontaneous hydrolysis of BNPP.