Catalysis of electrophilic bromine attack by α-cyclodextrin

Abstract

The aqueous bromination of various aromatic and heteroaromatic substrates is catalysed by α-cyclodextrin (α-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 α-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 α-CD varies little for substrates having a 10¹⁰ range of reactivity.