Aqueous emulsions of a variety of hydrocarbons under cobalt-60 irradiation have been allowed to react with molecular oxygen at pressures of 1-4 atm at 50°. Unlike the effect observed in polymerization, emulsification of styrene had no significant effect on the oxidation rate or products as compared to that observed in hydrocarbon solution. With emulsions of styrene and -methylstyrene, dependency on the rate of initiation and temperature is consistent with the bulk mechanism, and the product distribution qualitatively parallels bulk oxidations. Other hydrocarbons investigated include cyclohexene, cyclopentene, tetramethylethylene, tetralin, and cumene.
Radical-initiated oxidations of isobutylene in benzene solution at 80 and 147°and several atmospheres of total pressure are compared with gas-phase oxidations at 147 and 197°and 0.1-0.5-atm total pressure. The isobutylene reacts mostly by the addition mechanism and all oxidations give mostly acetone, isobutylene oxide, and a high-boiling residue as primary products. Radical-initiated oxidations of cyclopentene have been investigated at 100°, from 9 M in the neat hydrocarbon to 0.025 M in chlorobenzene and from 0.027 M to 0.056 M in the gas phase. The rates and products of oxidation appear to be similar in the two phases. Gas-phase oxidations have also been carried out at 155°and good material balances obtained. The main primary product from oxidation of cyclopentene appears to be cyclopentenyl hydroperoxide, but this peroxide is less stable than the products from isobutylene or alkanes, and it causes autocatalysis and gives secondary products. The gas-phase decomposition of cyclopentenyl hydroperoxide was studied at 100°and the effects of some additives were determined. The principal product is cyclopentenol, but, in the presence of cyclopentene and oxygen and in many oxidations of cyclopentene, a high-boiling residue is obtained, apparently a secondary product.
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