The kinetics of methane oxidation by methane monooxygenase is simulated numerically. Literature data on the distribution of products of the oxidation of deuterated methane CH 4 − n D n (CH 3 D, CH 2 D 2 , and CHD 3 ), as well as on the kinetic isotope effect in the competitive oxidation of CH 4 and CD 4 by methane monooxygenase, are analyzed in the framework of a nonradical multistep mechanism. Kinetic schemes whose first step involves two hydrogen atoms of the oxidation substrate are considered. The kinetic models suggested for methane oxidation are in good agreement with experimental data.

Kinetic isotope effect data for the oxidation of deuterium-substituted methane molecules with methane monooxygenase (MMO) are analyzed in the framework of a multistep nonradical mechanism. New evidence is obtained in favor of the hypothesis of the intermediate formation of a complex containing pentacoordinated carbon. A kinetic scheme whose first step involves two hydrogen molecules of the substrate being oxidized is considered. For coincidence between the calculated and experimental distributions of the oxidation products of partially deuterated methane, the formation of the intermediate complex containing pentacoordinated carbon must be reversible and the rate of the back decomposition of this complex must be substantially higher than the rate of its formation (w −1 ≫ w 1). The experimental distribution of the products of deuterated methane (CH3D, CH2D2, and CHD3) hydroxylation with MMO, which could not earlier be explained within the widely accepted oxygen rebound mechanism, is quantitatively explained for the first time in terms of the dynamics of a nonradical mechanism using parameters having a simple physical meaning and plausible values.

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According to the mechanism of alkane hydroxylation, whose main postulate is the formation of an intermediate complex containing pentacoordinated carbon, the hydroxylation of methane and ethane by methane monooxygenase was kinetically simulated by the numerical method. The published data on the kinetic isotope effects of oxidation of deuterium-substituted methane molecules (CHD 3 , CH 2 D 2 , and CH 3 D) and the distribution of products of chiral ethane ( R - and S -MeCHDT) oxidation by methane monooxygenase were examined. The kinetic models proposed for the oxidation of isotopically substituted methane and ethane are in good agreement with experimental data.

Published data on the kinetic isotope effects of the hydroxylation of deuterium-substituted methane molecules (CHD 3 , CH 2 D 2 , and CH 3 D) by methane monooxygenase are examined in the framework of the two-step nonradical mechanism through the intermediate formation of a complex containing pentacoordinate carbon. The kinetic schemes with the first step involving one, two, and three hydrogen atoms of the oxidized substrate are considered. Contrary to the widely accepted oxygen rebound mechanism, the experimental results obtained for the oxidation of various substrates by methane monooxygenase and cytochrome P450 can be explained from the viewpoint of the dynamics of a general nonradical mechanism.

The kinetics of cyclohexane and cyclopentane oxidation by hydrogen peroxide catalyzed by iron porphyrins (FeTPP and FeTDCPP) in acetonitrile solutions is studied at room temperature by analyzing product accumulation with the GLC method. The effects of various additives (acetic acid, imidazole, and hydroquinone) on the substrate selectivity of the competitive oxidation of C 6 H 12 and C 5 H 10 are studied. In the FeTDCPP/H 2 O 2 /O 2 /AcOH/CH 3 CN system, cyclohexane is oxidized to the corresponding alcohol, ketone, and hydroperoxide. The fraction of the product (hydroperoxide) formed by the radical mechanism is 20–30%. The alcohol and ketone are formed by the molecular pathway in a ratio of (6–7) : 1. Kinetic parameters of cycloalkane oxidation are compared in a biomimetic system with hydrogen peroxide (the shunt system) and the system based on dioxygen with electron and proton donors. The latter system modeled cytochrome P-450. It is shown that active species are the same in both systems. The kinetic scheme of the alkane oxidation process is proposed for the shunt system.

The kinetics of the accumulation of cyclohexyl hydroperoxide, alcohol, and ketone during cyclohexane oxidation in an O2/FeP/AcOH/Zn/CH3CN biomimetic system is studied by gas-liquid chromatography. The factors determining the selectivity of the nonradical oxidation pathway, which results in the formation of more than 80% of the products, are considered. A scheme of the molecular pathway of alcohol and ketone formation is proposed, which agrees well with the experimental data. The kinetic parameters for cyclohexane oxidation catalyzed by iron porphyrins with various substituents in the phenyl rings in this system with and without an electron carrier (methylviologen) are calculated.

Conclusive arguments in favour of a new mechanism of saturated hydrocarbon oxidation were obtained. By the use of steady-state concentration method literature data on exogenous substrates (partially deuterated camphor, norbornane, ethylbenzene) isomerisation in the course of hydroxylation in enzymatic and biomimetic systems are analysed in terms of the new mechanism of oxidation via an intermediate complex containing pentacoordinated carbon. Kinetic parameters of hydrocarbon hydroxylation in various systems are calculated. A self-consistent pattern of the reaction dynamics in the terms of the mechanism proposed was presented.

The state-of-the-art of investigations in the field of catalysis of biological oxidation of saturated hydrocarbons by molecular oxygen and simulation of this process on the basis of metal complexes is reviewed.

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Literature data on substrate isomerization in the course of hydroxylation in enzymatic and model catalytic systems are analyzed in terms of a previously suggested mechanism of hydroxylation via an intermediate peripheral complex containing pentacoordinated carbon. Calculated kinetic parameters of hydroxylation reactions in various systems demonstrate that the mechanism suggested does not require dubious assumptions for obtaining a self-consistent pattern of the reaction dynamics in contrast to the commonly accepted oxygen-rebound mechanism.

Anisole was found to undergo selective oxidation with hydrogen peroxide catalyzed by methylrhenium trioxide to yield o- and p-methoxyphenols. The reaction kinetics was studied at 50 degrees C. The rate constants of o- and p-methoxyphenol formation in the absence and in the presence of a polar solvent (CH3CN) were determined for oxidation with aqueous and nonaqueous solutions of H2O2. The active intermediate attacking the C-H bonds in the benzene ring of anisole is assumed to be a strongly electrophilic nonradical species.

The kinetics of C6H12 oxidation is studied using GLC by the accumulation of products. The oxidation is accompanied by the reductive activation of molecular oxygen by iron porphyrins containing various substituents in phenyl rings. The experiments were performed at room temperature in the CH3CN-carboxylic acid-Zn system with and without methyl viologen. A scheme of oxygen activation during the oxidation of hydrocarbons is proposed.

The reactivity of cyclohexane and cyclopentane in the oxidation by molecular oxygen activated by iron and manganese porphyrins was studied. The experiments were performed in the presence of the reductant (zinc dust) and the proton donor (acetic acid) with and without methyl viologen in acetonitrile at room temperature. The kinetic isotope effect (KIE) of the reaction between C6H12 and the active species was measured by the method of competing reactions. The effects of different factors on the selectivity were studied. The mechanism of formation of oxidation products was proposed.

A new model for cytochrome P-450 activation of O2 on iron porphyrin as a catalytic centre in the presence of Zn(Hg) as a reducing agent, methylviologen as a mediator, and acetic anhydride as an acylating agent is proposed.

Flash photolysis was used to measure the rate constant for the reduction of Fe(III)-and Fe(II)O2-porphyrin complexes by methylviologen radical cations in acetonitrile.

Hexane oxidation by various liver microsomes fractions of noninduced and phenobarbitol- or methylcholantrene-induced rabbits (MR, MRPB, MRMC) has been studied. The relative reactivity of the C-H bond at the 1st, 2nd and 3rd carbon atoms has been shown to depend on the fraction nature and on the oxygen-activating system (NADPH/O2 or PhIO). The C3/C2 hexanol ratio is determined by steric factors of the hexane oxidation reaction. According to this parameter, the forms of cytochrome P-450 can be arranged in the following order: MRMC less than MRPB less than MR. The size of hydrophobic cavities connecting the substrate seems to decrease in the same order. The data obtained suggest that microsomes contain a cytochrome P-450 fraction which oxidizes alkanes only at the terminal methyl group. The regioselectivity of hexane oxidation in the P-450-NADPH-O2 and P-450-PhIO systems has been compared. These systems have been shown to generate different particles responsible for hydroxylation.