The hydrolysis of propyl benzoate in aqueous solutions of surface-active agents

Abstract

Abstract The effect of cetrimide and sodium lauryl sulphate on the alkaline hydrolysis of emulsions and solutions of n-propyl benzoate has been investigated and compared with results obtained previously in cetomacrogol solutions. Evidence is presented to show that the rate of reaction depends on the degree of saturation of the dispersion expressed as a “Saturation Ratio”, which is the ratio of ester concentration to its solubility in a given concentration of surface-active agent. The hydrolysis rate of solubilised ester decreases with increase in surface-active agent concentration while the effect of such an increase in concentration on the hydrolysis rate of emulsified ester depends on the nature of the surface-active agent. The initial rate in sodium lauryl sulphate and cetomacrogol is independent of concentration, but in cetrimide the rate increases with cetrimide concentration until sufficient is present to solubilise the ester.