Cyclohexane, hydroxylation

Mnm(Por)X also catalyze oxygen transfer from iodosobenzene to hydrocarbons.12 The reactions are apparently stepwise, for example, cyclohexane hydroxylation accompanies halogenation by the counterion X, and cis-stilbene gives a mixture of cis- and trans-stilbene oxide (1.6 1). The active species is proposed to be O—Mnv(Por)X. 

Table IX.4 gives the distribution of isopentane hydroxylation products in various systems, including photochemical hydroxylation by hydrogen peroxide, where free hydroxyl radicals are known to be formed as intermediates. It is clear that the ratios of selectivities with respect to the site of attack (1° 2° 3°) in the systems involving and ions are very close to each other and to the selectivity observed for the attack by hydroxyl. This leads to the conclusion [47c] that the same active species (presumably hydroxyl radicals) participates in all these systems. This is also supported by a low isotope effect (kuJkn 1.2-1.3, when comparing reactions of C6H12 and C6D12). The yield of cyclohexane hydroxylation products depends on the nature of the solvent. The high yields in acetonitrile as compared with the other solvents are to be expected, provided the hydroxyl radicals are the intermediate active species. The rate constant of the hydroxyl radical reaction with cyclohexane is 5 lO dm mol s , with...

Fig. 2. Photochemical action spectrum of the reversibility of the carbon monoxide inhibited cyclohexane hydroxylation in rat liver microsomes. From )...

A computer analysis of the biphasic kinetics revealed a turnover number of about 66/min for the hemoprotein-cyclohexane complex, which agreed with the specific activity of cyclohexane hydroxylation based on the amount of high-spin complex formed after addition of cyclohexane ... 

Table 10. Cyclohexane hydroxylation by cumen hydrogenperoxide or PhIO catalyzed by various metalloporphyrins [284] ...

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