The Effects of Surfactants on Hydrolysis of r-Phenyl-r-butyrolactone

Abstract

The hydrolysis of r-phenyl-r-butyrolactone in 20% aqueous acetone solution has been examined in the presence of sodium dodecyl sulfate (SDS), dodecyltrimethylammonium chloride (DTAC) and polyethyleneglycol-(p-nonylpheny1)-ether (PONPE) at O.0, 2.5 and 5.0°C.
The results obtained were as follows.1) The kinetic and thermodynamic parame ters of the reaction were evaluated for each surfactant. The reaction was found to be accelerated in micellar systems. Linear relationships are present between E_A and S_A and between k_ObB and concentration of surfactants.2) In gel filtration on a Sephadex LH-20 column, samples of SDS, DTAC and PONPE at concentrations above the CMC behaved similarly to polymerizing systems. From the gel filtration data, partition coefficients of solutes in micellar and bulk phases were calculated.3) γ-Phenyl-r-butyrolactone was strongly partitioned in micellar phases of the surfactants, especially in those of PONPE and DTAC. NaOH was weakly partitioned especially in micellar phases of SDS. This is because there is a repulsion between the negatively charged micelle of the anionic surfactant and the hydroxide anion.4) From the kinetic data for bulk and micelle phases (k_b and k_m), it was found that the reaction was accelerated principally due to lowering of the entropy of activat ion.