CATALYSIS OF ELECTROPHILIC BROMINE ATTACK BY ALPHA-CYCLODEXTRIN

The aqueous bromination of various aromatic and heteroaromatic substrates is catalysed by alpha-cyclodextrin (alpha-CD), and the oxidation of formic acid (by bromine attack on formate ion) is similarly catalysed. The kinetic results are interpreted in terms of reaction between free substrate and the alpha-CD.Br2 complex, which is slightly more reactive than free bromine. This interpretation is consistent with the finding that substituent effects for the catalysed and uncatalysed reactions are essentially identical and that the transition state stabilization afforded by alpha-CD varies little for substrates having a 10(10) range of reactivity.