Molecularity, Bond-Fission and Reaction Mechanism in the Acid Hydrolysis of p-Propoxy Aniline Phosphate Diester Via Conjugate Acid Species

Kinetic study of the hydrolysis of p-propoxy aniline phosphate diester has been carried out from 0.1 to 6.0 mol dm-3 HCl at 97 ? 0.5 ?C in 20 % aqueous dioxin mixture. The diester has been found to be reactive via conjugate acid, neutral and mononegative species, but in this discussion only conjugate acid species are given. The rate of hydrolysis of inorganic phosphate obtained has been estimated by Allen's modified method [1]. The concentration of the diester in all kinetic runs was maintained at 5.0 ? 10-4 mol. dm-3. The pseudo first order rate coefficients have been calculated by using Debye - Huckle equation [2]. Ke = KH+. CH+. exp. ? Factors such as hydrogen ion concentration, ionic-strength, temperature, substrate concentration etc. have been studied to find out the participation of water molecule, bond-fission and molecularity of the reaction. Ionic strength data and pK values were used to estimate theoretical rates in various zones of pH - log rate profile of the reactive species Molecularity of the reaction has been discussed in terms of concepts such as Hammett acidity function [3, 4], Zucker - Hammett hypothesis [5] and Bunnett parameters [6]. Kinetic rate data and isokinetic relationship [7, 8] has been employed to suggest bond - fission of the reaction.