Kinetics of oxidation of alkanes and their derivatives byn-decanepersulfonic acid

Abstract

The kinetics of interaction of n-decanepersulfonic acid with linear, branched, and substituted hydrocarbons was studied. The oxidation of cvclo-C6HI~'C6Di2 occurs with a moderate kinetic isotope effect, kH/k D = 2.2+0.3. A satisfactory, correlation between the partial rate constants and the structure of hydrocarbons in terms of the Okamoto--Brown equation was found, Key words: persutfonic acid, alkanes, oxidation, kinetics.It has previously I been found for decane and cyclohexane that n-decanepersulfonic acid (RSO2OOH) efficiently oxidizes hydrocarbons to alcohols. The main channel of RSO2OOH consumption is its reaction with the oxidized substrate (R'H). It has been shown 2 for some alcohols and hydrocarbons that the kinetics of RSO2OOH consumption is described by the following equation:where C is the concentration of RSO2OOH; R'H is the oxidized substrate; k'/s -t is the experimental rate constant calculated from the semilogarithmic anamorphoses of the kinetic curves of RSO2OOH consumption ~q(Co/C) = k'f); and k]/s -I and k2/L tool -~ s -I are the rate constants of the following overall reactions, respectively:The reaction product P is an alcohol in hydrocarbon oxidation or ketone in alcohol oxidation. We have measured the k 2 rate constants for some hydrocarbons and alcohols and observed a correlation between their values and the substrate structure in terms of the Okamoto--Brown equation. 2 In this report, which continues our previous workfl we studied the influence of the nature of substituents at the CH group on its reactivity in the oxidation by decanepersulfonic acid for a wide range of substrates.Experimental n-Decanepersulfonic acid was synthesized by a known procedure, t Carbon tetrachtoride and the hydrocarbons were purifled by standard procedures. 3 Kinetic experiments were carried out as described previously. 2 The reaction kinetics was monitored by the consumption of persulfonic acid whose concentration was determined iodometrically. 4 Alcohols and ketones were analyzed by GLC and. in particular cases, by GC-MSfl Results and DiscussionThe reaction kinetics was studied in the 303--343 K temperature range in air using CC14 as the solvent. All experiments were carried out with the substrate concentration [R'H]0 >> Co. Under these conditions, the k' values are almost independent of the C O value and increase proportionally to increase in the amount of substrate added to the solution, i.e., in full correspondence with Eq. (1). The rate constant k~ has been previously 5 determined (at 323--343 K): log k 1 = (8.48_+0.56) -(85.3• (0 = 2.303RT kJ mol-~). The k I value estimated from the dependence of k' on [R'H]0 satisfactorily agrees with this equation. The k 2 values and its Arrhenius parameters (A 2 and E 2) for various substrates and temperatures are presented in Table I. h follows from these data that the linear dependence between the log A 2 and E 2 values is fulfilled (the compensation effect) within particular classes of the substrates under study: tog A 2 = --6.4 + 0.19E 2 (r = 0.954. hydrocarbons),...