Toluene derivatives, benzylic oxygenation

Oxidation of ortho-xylene. The spectra of the adsorbed species arising from interaction of ortho-xylene with the surface of the vanadia-titania catalyst in the presence of oxygen are shown in Figure 4. The spectra show some parallel features with respect to those discussed above concerning the oxidation of toluene and meta- and para-xylene. Also in this case the o-methyl-benzyl species begins to transform above 373 K, with production of adsorbed o-tolualdehyde (band at 1635 cm 0 and of a quinone derivative (band at 1670 cm. Successively bands likely due to o-toluate species (1530,1420 cm 0 grow first and decrease later with production of CO2 gas. 

Oxygen Nucleophiles. A reagent such as permanganate oxidizes toluene to benzoic acid, whereas benzylic oxidation by palladium acetate results in benzyl alcohol derivatives. The oxidation is favored by electron-releasing substituents in the phenyl ring. Catalytic amounts of palladium acetate and tin diacetate, in combination with air, effects an efficient palladium-catalyzed benzylic oxidation of toluene and xylenes. For the latter substrates, the Q, Q -diacetate is the main product.A mixed palladium diacetate-copper diacetate catalyst has also been found to selectively catalyze the benzylic acyloxylation of toluene (eq 64). ... 

It should also be emphasized that benzyl radicals can be formed from toluene by hydrogen atom abstraction reactions. This may involve, for example, reaction with reactive oxygen-centered radicals derived from the photolysis of peroxides (see Amino Acids and Peptides later in this chapter). 

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