The oxidation of tetralin and cyclohexene by was investigated in the presence of cationic phase-transfer O 2 catalysts (PTCs). It was found that the oxidation takes place analogously to the recently investigated catalysed decompositions of hydroperoxide initiator molecules. The natures of both the onium cation and the counteranion are determining factors. The catalytic activity of the onium salt is determined by the e †ective charge on the onium ion and by the size and polarizability of the anion. For both hydrocarbons, the primary product of oxidation is the corresponding hydroperoxide, which may undergo further oxidation. For tetralin, tetralyl hydroperoxide underwent disproportionation into and tetralol, and reuse of the thus produced O 2 O 2 resulted in a considerable "" overoxidation ÏÏ in the closed reactor. Tetralone was formed in a smaller amount. The main products in the oxidation of cyclohexene were its hydroperoxide, cyclohexene oxide and 2-cyclohexen-1-ol. In contrast to the oxidation of tetralin, "" overoxidation ÏÏ did not occur here, and the formation of 2-cyclohexen-1-one was never observed. The oxidations of these hydrocarbons in the presence of cationic PTCs proved to be strongly inÑuenced by the concentration of homogeneously dissolved water. The oxidation products of these hydrocarbons also exerted considerable inÑuence on the progress of the oxidation.
Experimental and theoretical evidence is presented that cationic phase-transfer catalysts promote the homolytic decomposition of hydroperoxide initiators into radicals, this being a fundamental step in the catalysis of the oxidation of hydrocarbons bySuch decomposition of the model substance tert-butylwas found to have a value of 2, independently of the nature of the /*O 2 counteranion present. It is assumed that the interaction between hydroperoxide and onium cation is mainly electrostatic in nature and that its e †ectivity depends on the positive charge density on the onium cation, which is controlled by the nature and dimensions of the counteranion. The role of water in the decomposition of t-BHP is also elucidated.
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