Kinetics and selectivity of the oxidation of alkanes in Cl2?H2O and Cl2?Hg2+?H2O solutions

Relative oxidation rate constants of several normal, iso-, cyclo-and methylcycloalkanes have been measured in Cl₂–H₂O and Cl₂–Hg²⁺–H₂O solutions at 343K. The selectivity of C–H bond dissociation in both systems is the same. HOCl is assumed to be the active species for the two systems.

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Cl₂–H₂O Cl₂–Hg²⁺–H₂O 343 , -,- ; C–H . , HOCl.

     

Kinetics of catalytic oxidation of aliphatic alcohols in aqueous alkaline solutions of copper phenanthroline complexes

The effect of Cu(II), phenanthroline, alcohol, NaOH and O₂ concentrations on the oxidation rates of alcohols in aqueous alkaline solutions has been studied and a reaction mechanism is proposed.

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Cu(II), , , NaOH, O₂ - . .

     

Temperature Dependences of the Kinetic Isotope Effect and the Ratio of the Reaction Rates for Reaction of Cyclopentane and Cyclohexane with HOCl in Water

We have determined the activation parameters logA and E for the Arrhenius equations for the kinetic isotope effect (c-C₆H₁₂/c-C₆D₁₂) and the 5/6 effect (c-C₅H₁₀/c-C₆H₁₂) in reactions of the C—H bonds of cycloalkanes with HOCl in aqueous solutions in the interval 30-90 °C. The data obtained are consistent with a chlorination mechanism including a pre-activation step with formation of an HO^· ... Cl^· pair, linear abstraction of the H atom by the OH group and angular attack by the Cl atom "at a distance" on the carbon atom.     

Temperature dependence of the ratios of the rate constants of hydroxylation of the cycloalkanes C6H12/C6D12 and C5H10/C6H12 in sulfuric acid

The temperature dependence of the ratios of the rate constants k(C₅H₁₀)/k(C₆H₁₂) and k(C₆H₁₂)/k(C₆D₁₂) for the reaction of the cycloalkanes C₅H₁₀, C₆H₁₂, and C₆D₁₂ with OH⁺ cations in the system (NH₄)₂S₂O₈ (0.1 mol/kg)-H₂SO₄ (94.4 mass %) in the 6–50 °C range has been studied. The activation energies found E(C₆H₁₂) − E(C₅H₁₀) = − 5.3 ± 0.3 and E(C₆D₁₂) − E(C₆H₁₂) = 7.9 ± 0.7 (kJ/mol) permits the comparison of OH⁺ to a group of reagents (NO₊², Pd²⁺, HSO₊³) which interact with the C-H bond via an electrophilic substitution mechanism. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 44, No. 6, pp. 354–358, November–December, 2008.     

Kinetics and mechanism of the reactions of C6H12, C5H10 and C6D12 cycloalkanes with peroxynitrous acid in aqueous solution and the gas phase

The c-C₆H₁₂/c-C₆D₁₂ kinetic isotope effect (KIE), the k₆/k₅ rate constant ratio (c-C₆H₁₂/c-C₅H₁₀), and the temperature dependence of these ratios in the gas-phase reactions of cycloalkanes with peroxynitrous acid and OH radicals are identical. The same result was obtained for the reactions in aqueous solution. These data are in accord with the conclusion that OH^· radicals formed in the homolysis of the HO-ONO bond are the active species in the reactions of HOONO with hydrocarbons in aqueous solution and in the gas phase. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 44, No. 2, pp. 105–110, March–April, 2008.