The oxidation of vicinal diols by hexamethylenetetramine^bromine (HABR) proceeds by a glycol-bond fission via an intermediate complex whereas non-vicinal diols behave like monohydric alcohols towards HABR.Hexamethylenetetramine ^bromine (HABR) has been reported as an oxidizing reagent in synthetic organic chemistry 1Y2 and mechanistic aspects of the oxidation of alcohols by HABR have been reported. 3 However, there seems to be no report on the oxidation of diols by HABR. Here, we report the kinetics of the oxidation of several vicinal and non-vicinal diols, viz. ethanediol, propane-1,2-diol, butane-1,2-diol, butane-2,3-diol, pinacol, propane-1,3-diol, butane-1,3-diol, butane-1,4-diol, pentane-1,5-diol and the monoether 3-methoxybutan-1-ol by HABR in glacial acetic acid solution and mechanistic aspects are discussed.HABR was prepared by the reported method 1 and its purity was checked by an iodometric method.[1,1,2,2-2 r R ]Ethanediol (DED) was prepared by reducing diethyl oxalate with lithium aluminium deuteride. 9 The reactions were studied under pseudo-¢rst-order conditions by using a large excess Â15 or greater) of the diols over HABR. The solvent was glacial acetic acid. The reactions were followed by monitoring the decrease in [HABR] at 394 nm for up to 80% reaction. The pseudo-¢rst-order rate constants, k os , were evaluated from linear least-squares plots of log[HABR] vs. time.The oxidation of vicinal diols by HABR yields products arising from glycol bond ¢ssion, i.e. rupture of the bond between the carbon atoms bearing the hydroxy groups, while the other diols give products by simple oxidation of one of the hydroxy groups. Analyses of products indicate the overall reactions (1) and (2).
