Structure–reactivity correlation for reactions of peroxide anion nucleophiles with substituted acyloxybenzenesulfonate bleach activators

Abstract

Second-order rate constants are reported for the reaction between a series of esteric bleach activators with different acyl substituents, namely, acetyloxybenzenesulfonate, n-butanoyloxybenzenesulfonate, n-nonanoyloxybenzenesulfonate and isononanoyloxybenzenesulfonate, and a set of peroxide nucleophiles whose basicity ranges from below that of the oxybenzenesulfonate leaving group to above it. The results conform to a Brønsted-type relationship with β_nuc, 0.42 ± 0.01 for acetyloxybenzenesulfonate, very similar to the value of 0.40 ± 0.01 for para-nitrophenyl acetate and a range of peroxide nucleophiles. A significantly larger value of β_nuc, 0.56 ± 0.05 is obtained with n-nonanoyloxybenzenesulfonate. This increase in β_nuc is interpreted in terms of steric and polar interactions between the acyl substituent and the attacking nucleophile. The reactivity of n-butanoyloxybenzenesulfonate is similar to that of n-nonanoyloxybenzenesulfonate whilst that of isononanoyloxybenzenesulfonate is less. These results are discussed in terms of the practical consequences for bleach activation and with regard to the mechanism of acyl transfer from esters to peroxides.