Methoxy radicals, decomposition

Hoare and Wellington (22) produced CH3O radicals from the photochemical (50° and 100°C.) and thermal (135°C.) decompositions of di-terf-butyl peroxide in the presence of 02. The initially formed tert-butoxy radicals decomposed to acetone plus methyl radicals, and the methyl radicals oxidized to methoxy radicals. Formaldehyde and CH3OH were products of the reaction the formation of the former was inhibited, and the latter was enhanced as the reaction proceeded. If the sole fate of CH3O were either... 

In an elegant four laser experiment Temps [46] has also investigated the variation in k E) for the decomposition of the methoxy radical ... 

The question of rearrangement in acyloxy radicals is still unsettled. In the case of the decomposition of -methoxy- -nitrobenzoyl peroxide rearrangement is observed, but the other circumstances indicate a polar mechanism for the reaction.118... 

Although benzoyl peroxide will initiate the polymerization (by a radical chain reaction) of either styrene or acrylonitrile, -methoxy- -nitrobenzoyl peroxide will not initiate polymerization efficiently in the latter monomer because it is too rapidly destroyed by the polar decomposition. Acrylonitrile, but not styrene, causes the polar decomposition to predominate, and the intermediates of the polar decomposition are not catalysts for the polymerization of acrylonitrile. 

There is considerable overlap in the effective range of the initiators, but this is less troublesome than it might seem since the various mechanisms can be expected to differ in their response to inhibitors. And if the alternatives are free radical and ion-pair with one of the possible ions not very reactive, decision is easy. For example, the polar decomposition of >-methoxy-/> -nitro benzoyl peroxide in acrylonitrile initiates... 

More convenient for the formation of aryl fluorides 4 is the decomposition of triazenes with hydrogen fluoride/pyridine (70 30 w/w) mixture, easier to handle than pure hydrogen fluoride. In this case, decomposition is performed at a lower temperature (18-50°C) and acetic acid, for example, is a suitable solvent.299 However, radical side reactions can be more pronounced, especially with bromo-, iodo-, nitro- or 2-methoxy-subslituted substrates. 

A paper by Gierer et al. [63] probably resolves the mechanism. These workers found that a number of hydroxy- or methoxy-substituted stilbenes would react with hydroxyl radicals, or with a combination of superoxide and hydroxyl radicals. The formation of superoxide and hydroxyl radicals by hydrogen peroxide decomposition is hard to prevent and incomplete chelation of metal ions might explain the inconsistent results reported by the earlier workers. 

If the /7-position of the amine is blocked by methoxy, methyl, chlorine or bromine groups, the species is stable with respect to dimerisation and higher anodic potentials are required for its further oxidation. However, further decomposition of the tri /7-anisylamine radical cation occurs in the presence of any traces of cyanide ion present in the acetonitrile solution. Primary aromatic amines, like phenols, tend to polymerise upon oxidation unless the o and p positions are blocked. 2,4,6-tri-t-butylaniline in acetonitrile solution yields a fairly stable radical cation which in the presence of water forms 3,5-di-f-butyl-4-amino-2,5-cyclohexadienone. ° ... 

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