Kinetics and Mechanism of Hydrolysis of 2,5-Dichloro Aniline Monophosphate in Hydrochloric Acid Medium

Abstract

Kinetics of the hydrolysis of 2,5-dichloro aniline monophosphate has been investigated in acid medium (0.1 to 7.0 mol dm^–3 HCl) at 80ºC and the spectrophotometric method is employed for the estimation of inorganic phosphate, the ultimate product of hydrolysis. pH log rate profile has a rate maxima at 4.0 mol dm^–3 HCl. Hydrolysis of the monoester in the acid region has been shown to be mainly via their conjugated acid species and the contribution of the neutral species is negligibly small. Rate data at constant ionic strength was used to identify reactive species and to determine theoretical rates. Theoretical rates, estimated from second empirical terms of Debye-Huckel equation, have been found to be in close agreement with experimental rates. Arrhenius parameters concept of molecularity and other kinetic rate data support a bimolecular nucleophilic attack of water on the phosphorus atom of the conjugate acid species of 2,5-dichloro aniline monophosphate. The suitable mechanistic steps involving the formation of transition state in which the charges are dispersed is proposed. Kinetic rate data and isokinetic relationship have been used to propose the probable P-N bond fission.