Reaction pathways dimethylphenol

In these equations, Cu202, DMP, and DPQ denote [Cu(HB(3,5-Me2pz)3)]2(02), 2,6-dimethylphenol, and the diphenoquinone, respectively. The rate expressions clearly indicate the occurrence of two competitive reaction pathways ascribed to (1) the spontaneous O—O bond homolysis of the p.-7j2 tj2 peroxo complex and (2) acid/base replacement of the peroxo group with phenoxide to give a phenoxo copper(II) interme-... 

Another proposed mechanism of the polymerization is a two-electron transfer mechanism, which involvs phenolate-bridged dinuclear copper(II) complex as starting species. The complex generated phenoxonium cations and phenolate anion through a double one-electron transfer from a phenolate to both copper centres (step v) and form the quinone-ketal intermediate via nucleophilic attack (step vi). This reaction pathway is supported by theoretical calculations of atomic charges of monomeric and dimeric species of 2,6-DMP where phenoxonium cations are proposed as key intermediates. Ab Initio calculations on 2,6-DMP and 4-(2,6-Dimethylphenoxy)-2,6-dimethylphenol provided evidence of the phenoxonium cation in the copper-catalyzed oxidative coupling reaction which proposed that the selective C-O coupling was achieved via the nucleophilic attack of a phenolate on the para-carbon of a phenoxonium cation (25). Based on the experimental evidence currently reported, both... 

The classical and the most useful laboratory method for the preparation of quinones is the oxidation of monohydric phenols with the radical reagent, potassium nitrosodisulphonate [(K03S)2NO] (Fremy s salt) (the Teuber reaction).5 Details for the conversion of 3,4-dimethylphenol into 3,4-dimethyl-1,2-benzoquinone may be regarded as typical55 the probable mechanistic pathway is formulated below. 

Figure 19.3 Optimized structure of the reactive species in the pathways corresponding to the reaction of 2,3-dimethylphenol with OH radical.

Thus, eight pathways are identified for the secondary reactions of OH with 2,3-dimethylphenol. Of all the pathways studied, pathways 5 and 6 leading to the formation of 3-hydroxy-2-methyl-2H-pyran-2-carbaldehyde (P5) and 7-methyl-2,8-dioxa-bicyclo[5,l,0]octa-3,5-diene-3-ol (P6) are found to be equally most favorable due to small barrier of 11.16kcalmol. ... 

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