Kinetics and mechanism of the oxidation of some vicinal and non-vicinal diols by tetrabutylammonium tribromide |
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Authors: | Jaya Gosain and Pradeep K Sharma |
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Institution: | (1) Department of Chemistry, JNV University, 342 005 Jodhpur, India |
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Abstract: | Kinetics of oxidation of five vicinal and four non-vicinal diols, and two of their monoethers, by tetrabutylammonium tribromide
(TBATB) has been studied. The vicinal diols yield products arising out of glycol-bond fission, while the non-vicinal diols
produce the hydroxycarbonyl compounds. The reaction is first-order with respect to TBATB. Michaelis-Menten type kinetics is
observed with respect to diols. The reaction fails to induce the polymerization of acrylonitrile. There is no effect of tetrabutylammonium
chloride on the reaction rate. The proposed reactive oxidizing species is the tribromide ion. The effect of solvent composition
indicates that the rate increases with increase in the polarity of the solvent. The oxidation of 1,1,2,2-2H4] ethanediol shows the absence of any primary kinetic isotope effect. Values of solvent isotope effect, k(H2O)/k(D2O), at 288 K for the oxidation of ethanediol, propane-1,3-diol and 3-methoxybutan-1-ol are 3.41, 0.98 and 1.02 respectively.
A mechanism involving a glycol-bond fission has been proposed for the oxidation of vicinal diols. Non-vicinal diols are oxidised
by a hydride-transfer mechanism, as they are monohydric alcohols. |
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Keywords: | Correlation analysis vicinal and non-visinal diols tetrabutyl-ammonium tribromide |
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