Reaction kinetics on hydrolysis of substituted di-phenyl phosphate ester in different borate buffers

Abstract

The reaction of hydroxide ion with di-4-methyl phenyl phosphate has been studied in the presence of micelles of cationic detergent. It has been investigated at pH 8.0 to 10.0 at 40 ± 0.10 °C in aqueous dioxane di-phosphate esters. Pseudo-first order rate constants k ψ and k' w have been measured spectrophotometrically by rate of appearance of inorganic phosphate during hydrolysis. k ψ and k' w were rate constants with and without CTAB, which varied in between 0.02 x 10 -3 to 2 × 10 -3 mol dm -3 and the concentration of phosphate was restricted to 5.0 x 10- 3 s -1 . Rate constants increase with concentrations of CTAB, giving at rate maximum. k ψ = 67.03 × 10 -5 s -1 at 18 x 10- 3 mol dm -3 CTAB and k ψ = 52.43 × 10 -5 s -1 at 16 x 10- 3 mol dm -3 CTAB respectively at pH 8.0 and 9.0 for di-anions of 4-mpp. The values of ion exchange parameter calculated at pH 8.0 and 9.0 by using various ion exchange equations have been summarized. The activation energy is 25.08 kcal/mol and entropy is 52.07 [-ΔS(eu)], which has been found at pH 8.0 and used borate buffer 3.9 x 10 -3 mol dm -3 [OH - ].