Solvent effect on the α-effect for reaction of p-nitrophenyl diphenylphosphinate with N-methyl 4-methoxy benzohydroxamate ion

Abstract

Second order rate constants have been measured spectrophotometrically for the reaction of p-nitrophenyl diphenylphosphinate with N-methyl 4-methoxy benzohydroxamate ion in dimethylsulfoxide–water and acetonitrile–water mixtures (10–70% v/v) at 27 °C. The reactivity of hydroxamate ion towards p-nitrophenyl diphenylphosphinate increase upon addition of dimethylsulfoxide where decrease upon addition of acetonitrile into the reaction medium up to 10% (v/v) and is followed by a gradual increase upon further additions. The reactivity of α-nucleophile hydroxamate ion has been compared with normal nucleophile p-chlorophenoxide ion. The kinetic results have been explained on the basis of p K a, α-nucleophile and differential solvent effect.