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The characteristics of the initial step in the reaction of ozone with saturated hydrocarbons have been investigated. Ozonation of cyclohexane gives initially cyclohexanol and cyclohexanone in a 3:1 ratio. Cyclohexane is oxidized 4.5 times more rapidly than cyclohexane-d 12 . The relative reactivity of primary, secondary, and tertiary hydrogens is approximately 1:13:110. The ozonation of tertiary hydrogens to tertiary alcohols occurs with 60 to 70% retention of configuration. The presence of good hydrogen atom donors, antioxidants, and a number of other reagents has only a small effect on the percent retention of configuration. These results and others are compared with those obtained for other hydrocarbon reactions, and a mechanism for the ozonation is suggested. Asa result of our interest in the mechanism of biological oxidations of saturated hydrocarbons (II), we have investigated the mechanisms of several alkane oxidations (12, 13). This paper reports our studies on the oxidation of saturated hydrocarbons by ozone. Although there are frequent references in the literature to the oxidation of alkanes by ozone(2), the mechanism of the reaction has received relatively little study.Durland and Adkins (7) reported that cis-and Jrans-Decalin are oxidized in reasonable yield to tertiary alcohols with retention of configuration.Schubert and Pease (24) studied the gas-phase ozonation of alkanes at room temperature and suggested that the products arose from the forma tion and further reactions of RO' and HOO*. A complicating feature in these investigations was the necessity to carry out the oxidation to rela tively high conversions so that the products could be analyzed. Since 15 Downloaded by MICHIGAN STATE UNIV on February 19, 2015 |

The characteristics of the reaction of ozone with alkanes at ambient temperatures have been investigated further. When 02 is replaced by N2 as the 03 carrier gas the following characteristics are not altered significantly: the ratio (0.3) of ketone to alcohol products formed from cyclohexane; the stereochemistry (60-70% net retention of configuration) of tertiary alcohol formation; and the relative reactivities (1:13 :110) of primary, secondary, and tertiary carbon-hydrogen bonds. The stereochemical results are unchanged by performing the ozonation in polar solvents, but a somewhat higher (82 %) net retention of configuration is observed in an alkane solvent (octadecane) of higher viscosity, and lower per cent retentions are observed when additives or solvents with which Os reacts are present. When the ozonations are performed in the presence of FeCl3, alcohols are formed with virtually 100% retention of configuration. Alkyl halides with essentially 100% inversion of configuration are also formed under such conditions. The effects of FeCl3, diphenylamine, and combinations of the two on the ratios of products (ketone, alcohol, and alkyl halide) formed on ozonation of cyclohexane were also determined. The Hammett p for the oxidation of substituted toluenes was found to be -2.07. The mechanism which best fits the data is one in which the ozone and alkane react to give either singlet 02 and the alcohol with retention of configuration, or triplet 02 and a triplet solvent-caged radical pair. The latter is either trapped by FeCl3 to give alkyl halide, or the radicals diffuse apart and react further to give the other observed products.ecently, there has been considerable interest in the mechanism of oxidation of carbon-hydrogen bonds by ozone. 71; (b) taken from the Ph.D. Thesis of T. . H., The Pennsylvania State University, 1970.(2) H.M. White and P. S.

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