Kinetics of the liquid-phase oxidation of 2-hydroxycyclohexanone

Abstract

The kinetics of oxygen uptake in the azobisisobutyronitrile-initiated oxidation of 2-hydroxycy-clohexanone (RCH(OH)C(O)R) at 323 K has been investigated (chlorobenzene solvent, [RCH(OH)C(O)R] = 0.15-1.30 mol/L, initiation rate of wi = 0.016–0.473 mol L−1 s−1). The effective oxidizability parameter kp, eff(2kt,eff)−0.5 has been determined by solving the inverse kinetic problem using the entire data array obtained while varying [RCH(OH)C(O)R] and wi. The rate constants of chain propagation and termination and the equilibrium constant of the addition of the hydroxyperoxyl radical to the ketoalcohol have been derived from the dependence of the oxidizability parameter on the substrate concentration. The rate constant of bimolecular chain initiation has been calculated to be k0 = 9.7 × 10−7 L mol−1 s−1. The ratio of the rate constants of quadratic-law peroxyl radical recombination reactions without and with chain termination (keff′/kt,eff′) increases with increasing [RCH(OH)C(O)R], passes through a maximum at a substrate concentration of 0.8 mol/L, and then falls off. It is demonstrated that this effect is due to the variation of the proportions of the hydroperoxyl and organic (1-hydroxy-2-oxocyclohexylperoxyl or 1,2-dihydroxy-1-cyclo-hexylperoxyl) radicals in the reaction medium.