THE METAL-CATALYZED AUTOXIDATION OF TETRALIN: IV. THE EFFECT OF SOLVENT AND TEMPERATURE

The limiting rate of oxidation of tetralin catalyzed by cobalt, manganese, and copper decanoates has been measured in 12 solvents at 65 °C. This rate is generally determined by the kinetic condition that the hydroperoxide reaches a steady-state concentration but the experimental rates are smaller than expected in some solvents. Both cobalt and manganese are able to terminate reaction chains and they therefore act as inhibitors of the oxidation at high concentrations. The ratio of the propagation rate constant (k3) to the square root of the termination rate constant (k6) for the oxidation of tetralin in acetic acid solution is given by[Formula: see text]

THE METAL-CATALYZED AUTOXIDATION OF TETRALIN: III. CATALYSIS BY MANGANESE, COPPER, NICKEL, AND IRON

The catalysis of the autoxidation of tetralin by the decanoates of manganese, copper, nickel, and iron has been examined over a large concentration range at 50 °C. With all four metals the oxidation rate approaches a limit at high catalyst concentrations but in each case this limit is smaller than the theoretical maximum rate of oxidation of pure tetralin (Y. Kamiya etal. Can. J. Chem. 41, 2020 (1963)). However, upon dilution with an inert solvent, such as chlorobenzene, or with the metal acetates, acetic acid, the theoretical maximum rate is attained. The low limiting rates in pure tetralin are apparently due to the low solubilities of the catalysts and are not due to chain termination by the catalysts.

THE METAL-CATALYZED AUTOXIDATION OF TETRALIN: II. THE COBALT-CATALYZED AUTOXIDATION OF UNDILUTED TETRALIN AND OF TETRALIN IN CHLOROBENZENE

The catalysis of the autoxidation of tetralin by the cobalt salts of 10 organic acids has been examined at 50 °C over a concentration range from 2 × 10−6to 1.0 mole/l, of cobalt. The measured rate of oxidation reaches a limiting value at cobalt concentrations above 2 × 10−2mole/l., which is about half the expected limiting rate. The cobalt salt catalysts are deactivated during the oxidation, probably in the initiation reaction with hydroperoxide, each cobalt atom being capable of decomposing about 100 molecules of hydroperoxide. Upon correcting the measured limiting rate for cobalt deactivation and for the amount of tetralin consumed at the point where the rate reaches a maximum value an extrapolated limiting rate about equal to the expected value is obtained. Although no steady concentration of hydroperoxide occurs during the oxidation the results suggest that the limiting rate of oxidation is basically due to the same phenomena that produce a limiting rate for the cobalt-catalyzed autoxidation of tetralin in acetic acid (Y. Kamiya et al. Can. J. Chem. 41, 2020 (1963)).

THE METAL-CATALYZED AUTOXIDATION OF TETRALIN: I. INTRODUCTION. THE COBALT-CATALYZED AUTOXIDATION IN ACETIC ACID

The catalytic effect of transition metal salts on the rate of autoxidation of organic substances reaches a constant value at some critical catalyst concentration. Three possible explanations of this phenomena are critically examined. The cobalt acetate catalyzed autoxidation of tetralin in acetic acid has been reinvestigated and the limiting rate of oxidation at high cobalt concentrations has been shown to be due to the production of a steady-state concentration of hydroperoxide. The present results are in fair agreement with the experimental work of Woodward and Mesrobian (J. Am. Chem. Soc. 75, 6189 (1953)) and are in excellent agreement with theoretical predictions.