Polymer Effects under Pressure. III. Hydrolysis of Normal Alkyl Acetate Catalyzed by Dodecyl Hydrogensulfate Micelle

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Abstract
Measurements of the rates of hydrolysis of methyl, ethyl, propyl, and butyl acetates have been made to 2 kbar in water catalyzed by dodecyl hydrogensulfate (DSA) micelle at 40 °C. The rate of hydrolysis decreases with compression up to approximately 1 kbar and then increases above 1 kbar; methyl acetate differs in these respects. The inversion phenomenon under pressure has been explained by the incorporation of both the H3O+ ion and ester molecules into the micellar phase. The observed value of the over all activation volume at 1 atm ΔV* is −5.3±1 cm3/mol for methyl, 0.40±1 cm3/mol for ethyl, 9.7±1 cm3/mol for propyl, and 20±1 cm3/mol for butyl acetate, respectively. From the activation volumes of HCl and DSA micellar catalysts, the volume change accompanying the incorporation of the esters into the micellar phase ΔΔVmicelle, has been estimated to be 4.0±1 cm3/mol for methyl, 9.8±1 cm3/mol for ethyl, 18.7±1 cm3/mol for propyl, and 27.9±1 cm3/mol for butyl acetate, respectively. The values above have been explained in terms of the contribution to the hydrophobic interaction between the ester molecule and the micelle.