THE MECHANISM OF RUO4-MEDIATED OXIDATIONS OF SATURATED-HYDROCARBONS - REACTIVITY, KINETIC ISOTOPE EFFECT AND ACTIVATION PARAMETERS

The mechanism of the RuO4-mediated oxidations of saturated hydrocarbons have been studied by a kinetic investigation of the oxidation of cis-decalin (1), trans-decalin (2), cis-1,2-dimethylcyclohexane (3), trans-1,2-dimethylcyclohexane (4), endo-tricyclo[5.2.1.0(2.6)]decane (5), adamantane (6) and perdeuterio-cis-decalin (1-d18). The results could be divided into the reactivity of secondary and tertiary axial and equatorial hydrogen atoms. Second-order rate coefficients (k2/10(-4) M-1 s-1) at 30-degrees-C are: equatorial tertiary 4.0; axial tertiary 0.42; equatorial secondary 0.085; axial secondary 0.009. From the rates of cis-decalin and perdeuterio-cis-decalin k(H)/k(D) = 4.8 was obtained. It is proposed that the reaction proceeds either via a carbocation-perruthenate ion-pair or by a highly polar cyclic transition state with the ion-pair route as a minor, competing pathway.