Formation and reactivity of carboxyphenyl radicals in aqueous solution
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Carboxyphenyl radicals were generated in aqueous solutions by reacting the solvated electron with ortho-, meta-and para-chlorobenzoate. These radicals were found to add to chlorobenzoates and abstract hydrogen atoms from a H-atom donor. It was concluded that the rate constants for the addition of carboxyphenyl radicals to chlorobenzoate depend on steric hindrance, since ortho;carboxyphenyl radical adds to 2-chlorobenzoate [k(add) = (1.0+/-0.2) x 10(6) dm(3) mol(-1) s(-1)] an order of magnitude slower than para-carboxyphenyl radical to 4-chlorobenzoate [k(add) = (1.0+/-0.2) x 10(7) dm(3) mol(-1) s(-1)]. The products of these addition reactions were detected by GC-MS. All three carboxyphenyl radical isomers abstract a H-atom from 4-methoxybenzen thiol at the same rate [k(H-aps)similar to 1 x 10(9) dm(3) mol(-1) s(-1)], i.e. the position of the carboxylate group seems not to influence the rate of the II-abstraction reaction. (C) 1998 Elsevier Science Ltd. All rights reserved.