I. K. Winterborn, B. Meakin, D. Davies
1974
Citations
0
Influential Citations
6
Citations
Journal
Journal of pharmaceutical sciences
Abstract
The effect of cetrimonium bromide at a concentration above its CMC on the base-catalyzed hydrolysis of eight p-substituted ethyl benzoates was investigated. The p-substituents were chosen on the basis of their Hammett substituent constants and included nitro, cyano, acetyl, fluoro, hydrogen, methoxy, amino, and dimethylamino. Of these, the nitro and cyano esters showed an increase in rate in the presence of cetrimonium bromide whereas all the others showed a decrease in rate. Micellar rate constants were calculated from both kinetic and gel filtration data. Treatment of the results according to the Hammett relationship for the effect of p-substituents on the rate of aromatic side-chain reactions led to the hypothesis that the observed rate modifications are dependent not only on the p-substituent and the surface pH of the micelle but also on the dielectric constant at the surface of the micelle.