Autocatalytic alkaline hydrolysis of tri-n-butyl phosphate

Although the alkaline hydrolysis of tri-n-butyl phosphate, TBP, in homogene ous aqueous solution shows normal second order kinetics, the hydrolysis of a solution with a hydrocarbon diluent by concentrated sodium hydroxide at 3 88 K shows an induction period followed by an autocatalytic reaction. The r eaction starts with two liquid phases, and ends with three, the third phase consisting mainly of sodium di-n-butyl phosphate, NaDBP, together with hyd rocarbon, TBP, (BuOH)-O-n, H2O and NaOH. The autocatalysis arises from the fact that the third phase dissolves appreciable concentrations of both TBP and NaOH, and serves to bring the reactants together, although the second o rder rate constant for reaction in the third phase is not much greater than it is in water. As hydrolysis proceeds the volume of the third phase incre ases while the other phases shrink, thus increasing the rate and resulting in autocatalysis.