Kinetic investigations of the electrochemical bromination of peracetylated D-glucal in organic solvents

Cyclic voltammetry and ultramicroelectrodes were used to investigate the kinetic aspects of the electrochemical bromination of 3,4,6-tri-O-acetyl-D-glucal (1) in acetonitrile (AN), dichloromethane (DCM), and dimethylsulfoxide (DMSO). Qualitative and quantitative results, determined notably from the kinetic parameter [glucal]/nu representing the competition between glucal concentration and time, clearly showed that glucal bromination depended on the nature of both the solvent and the in situ electrogenerated reactive brominated species (Br-2 or Br-3(-)) obtained from the oxidation of a bromide salt. It was especially shown that Br-2 reacted more rapidly than Br-3(-) towards (1). On the other hand, the reactivity of both brominated species appeared to follow the solvent polarity order since the highest reactivity was obtained in DMSO whereas the lowest one was found in DCM