Polar and Radical Oxidations

These are oxidised by both Fe(III) and Cu(II) octanoates (denoted Oct) in nonpolar solvents at moderate temperatures . 80-90 % yields of the corresponding disulphide are obtained with Fe(III) and this oxidant was selected for kinetic study, the pattern of products with Cu(II) being more complex. The radical nature of the reaction was confirmed by trapping of the thiyi radicals with added olefins. Simple second-order kinetics were observed, for example, with l-dodecane thiol oxidation by Fe(Oct)3 in xylene at 55 °C (fcj = 0.24 l.mole . sec ). Reaction proceeds much more rapidly in more polar solvents such as dimethylformamide. The course of the oxidation is almost certainly... 

The explanation for the dichotomy between aromatic nitration versus de-alkylative oxidation in equation (84) lies in the dynamics of ion-radical triad (which is predictably modulated by solvent polarity and added inert salt). For example, the nonpolar dichloromethane favors aromatic nitration via a radical-pair collapse of ArH+, NO, 239 i.e.,... 

Lipid hydroperoxides and phospholipid oxidation products Lipid hydroperoxides are the major primary products of LDL oxidation. Lipid hydroperoxides (LOOH) are relatively polar, non-radical intermediates of... 

At temperatures low enough to suppress thermal decomposition, a nltrosamlde XIV In polar or non-polar solvents Is photolytlcally decomposed to amldyl and nitric oxide radicals 4,16,17,18), This Is In sharp contrast to the photostahility of nitrosamines in neutral solvents (Including acetic acid) (ii), although the pattern of photodecomposition Is similar to that of nitrosamines In dilute acidic conditions. However, the overall photolysis pattern of nltrosamldes Is complicated by disproportionation of nitric oxide and existence of a radical pair XV (20,21,22). ... 

A review has focused on differentiation between polar and SET mechanisms through kinetic analysis.82 hi two separate reviews, the effects of solute-solvent interactions on electron-transfer reactions have been described.83,84 A review of the behaviour of radical cations in liquid hydrocarbons has given particular emphasis to those with high mobility.85 A paper presents selected studies in the formation of radicals by oxidation with manganese- or cerium-based reagents and then- application to C—C bond formation by SET processes.86... 

Eq. 4.54 shows the reaction of n-heptanol (151) with Pb(OAc)4 under high-pressured carbon monoxide with an autoclave to generate the corresponding 8-lactone (152). This reaction proceeds through the formation of an oxygen-centered radical by the reaction of alcohol (151) with Pb(OAc)4,1,5-H shift, reaction with carbon monoxide to form an acyl radical, oxidation of the acyl radical with Pb(OAc)4, and finally, polar cyclization to provide 8-lactone [142-146]. This reaction can be used for primary and secondary alcohols, while (3-cleavage reaction of the formed alkoxyl radicals derived from tertiary alcohols occurs. 

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