The kinetics of oxidation of a series of monoatomic alcohols (methanol, 2-pro0anol, 2-butanol, 2-methyl-l-propanol, 2-chloroethanol, 1,3-dichloro-2-propanol, benzyl alcohol), hydroxyacetic acid. and t,3-butandiol (ROH) by dimethyldioxirane (1) was studied. The reaction kinetics obeys the second order equation w = k[ROH] [I]. The rate constants were measured in the range of 7--50 ~C. and the activation parameters were found. To describe the reaction rate constants as a function of the ROH structure, the two-parametric Taft equation was used, which takes into account both the polar and resonance substituent effects. Alcohol oxidation produces the corresponding carbonyl compounds, via., ketones from secondary alcohols and aldehydes from primary alcohols, in yields of at least 80%. The results were explained by the competition of the molecular (oxenoid) and radical mechanisms. The introduction of electron-withdrawing substituents into the alcohol molecule increases the contribution of the radical channel of the reaction.Key words: dimethyldioxirane, alcohols, rate constants, free radicals.In recent years, dioxiranes have been widely used for the oxidative functionalization of organic compounds. They possess some advantages as compared to conventional oxidants: mild conditions and high rates of reactions; chemo-, stereo-, and regioseleetivity; simple procedures of oxidation and separation of the reaction products. The reactions between alcohols and dioxiranes have been studied previously, t-6 The reaction between secondary alcohols (viz., propane-2-ol, octane-3-ol, cyclobutanol, cyclohexanol, norborneol, and ct-methylbenzyl alcohol) and methyl(trifluoromethyl)dioxirane affords the corresponding ketones. The oxidation of butan-l-ol by methyl(trifluoromethyl)dioxiranes produces butyric acid, whereas a tertiary alcohol, 2-methylpropan-2-ol, does not react with dioxiranes. 1 The acetophenone derivatives are the main products of the reaction of dimethyldioxirane with p-substituted ct-methylbenzyl alcohols. 2 Linear and cyclic 1,2-and 1,3-diols are oxidized by dimethyldioxirane and methyl(trifluoromethyl)dioxirane to c~-and 13-hydroxyketones. 3-6The kinetics of the oxidation of cyclohexanol by methyl(trifluoromethyl)dioxirane 1 and that of p-substituted ct-methylbenzyl alcohols by dimethyldioxiranes 2 have been studied. However, the activation parameters have been measured in only a narrow (20 ~ temperature range.This work is aimed at the study of the products, kinetics, and mechanism of the interaction between dimethyldioxirane and aliphatie monoatomic alcohols: methanol (2), propan-2-ol (3), butan-2-ol (4), 2-methylpropan-l-ol (5), 2-chloroethanol (6), and 1,3-dichloropropan-2-ol (7), as well as the related compounds: hydroxyacetic acid (8), benzyl alcohol (9), and butane-l.,3-diol (10) (ROH) in an acetone solution at 7.0--50.0 ~
ExperimentalAcetone of high purity grade was purified by distillation. Dimethyldioxirane (1} was synthesized by a known procedureT; water was removed from an acetone solution of dioxirane by free...
