Kinetics and mechanism of the oxidation of some diols by benzyltrimethylammonium tribromide

The kinetics of oxidation of five vicinal and four non-vicinal diols, and t wo of their monoethers by benzyltrimethylammonium tribromide (BTMAB) have b een studied in 3:7 (nu/nu) acetic acid-water mixture. The vicinal diols yie ld the carbonyl compounds arising out of the glycol bond fission while the other diols give the hydroxycarbonyl compounds. The reaction is first-order with respect to BTMAB. Michaelis-Menten type kinetics is observed with res pect to diol. Addition of benzyltrimethylammonium chloride does not affect the rate. Tribromide ion is postulated to be the reactive oxidizing species . Oxidation of [1,1,2,2-H-2(4)] ethanediol shows the absence of a kinetic i sotope effect. The reaction exhibits substantial solvent isotope effect, A mechanism involving a glycol-bond fission has been proposed for the oxidati on of the vicinal diols. The other diols are oxidized by a hydride ion tran sfer to the oxidant, as are the monohydric alcohols.