"Characterizing reactivity of benzyl esters in sodium dodecyl sulfate micelles"

Abstract

Purpose: To study the effect of changing structure of benzyl esters on its reactivity in sodium dodecyl sulfate micelles. Methods: Ester molecules with benzyl moiety were either purchased or synthesized. Alkyl groups of the esters were increased incrementally from one to six carbons, also, the location of the ester bond was shifted from the first carbon attached to the benzene ring as in benzyl acetate to three and six carbons awary from the benzene ring as in 3-Phenylpropylacetate and 6-Phenylhexylacetate. Hydrolysis reaction rate constants fro each compound were determined in borate buffer at pH 9 and in surfactant solutions at 40 degrees C. HPLC was used to separate reactants and products. Results: As the number of carbon atoms in the alkyl chain has increased, rate constant in buffer decreased according to an increase in the alkyl chain starting from methyl and ending with hexyl. In micelles, rate constants also decreased as the surfactant concentration increased, this effect can be attributed to an increase in partitioning of the ester molecules into micelles. Conclusion: Date suggests that benzyl acetate, propionate, butyrate, 3-phenylpropyl acetate and pentanoate are located inside the palisade layer of the micelles where water is present. In regard to the orientation of the ester molecules, comparing benzyl butyrate and 3-phenypropyl acetate rate constants in micelles, data suggests that hydrocarbon chains of both molecules were facing the surface of the micelle.