By oxidation of methyl groups

Althongh the degradation of naphthalene-2-carboxylate by Burkholderia sp. strain JT 1500 involves the formation of 1-hydroxy naphthalene-2-carboxylate, this is not formed from the expected (l/ ,25)-di-l,2-dihydrodiol-2-naphthoate. Possibly, therefore, the reaction is carried out by a monooxygenase, or a dehydration step is involved. Subsequent reactions produced pyruvate and o-phthalate that was degraded via 4,5-dihydroxyphthalate (Morawski et al. 1997). Degradation of naphthalene carboxylates formed by oxidation of methyl groups has already been noted. 

In the determination of benzene, interfering effects of dinitrotoluene and dinitroxylenes originating from toluene and xylenes are removed by oxidation of methyl groups with a chromic acid solution. Dinitrobenzene is stable during this oxidation process. After adding pyridine and alkalization of the diluted nitration mixture, the two layers are separated from each other. Sodium salts of nitrocarbonic acids formed by the oxidation remain in the aqueous layer, whereas m-dinitrobenzene passes into the pyridine layer. The pyridine layer is separated, methyl ethyl ketone is added and the red-violet colour is evaluated by photometry [18]. 

Thus, to build structures with reasonable concentrations of fused rings, at least one tetrafunctlonal monomer Is required. Such materials are generally more costly than mono- or dlfunctlonal compounds. Notable exceptions are those tetrafunctlonal materials obtainable by oxidation of methyl groups. 

A second example of a membrane-bound arsenate reductase was isolated from Sulfurospirillum barnesii and was determined to be a aiPiyi-heterotrimic enzyme complex (Newman et al. 1998). The enzyme has a composite molecular mass of 100kDa, and a-, P-, and y-subunits have masses of 65, 31, and 22, respectively. This enzyme couples the reduction of As(V) to As(III) by oxidation of methyl viologen, with an apparent Kra of 0.2 mM. Preliminary compositional analysis suggests that iron-sulfur and molybdenum prosthetic groups are present. Associated with the membrane of S. barnesii is a h-type cytochrome, and the arsenate reductase is proposed to be linked to the electron-transport system of the plasma membrane. 

Several oxidations of amines involved oxidation of methyl groups adjacent to tertiary amines to carbonyl groups. Oxidation by RuO /aq. Na(IO )/CCl of 2, 3, 5 -tri-0-acetyl- or -benzoyl derivatives of A A -dimethyladenosine, A, A -... 

Useful whole cell asymmetric oxidations of methyl groups to carboxyl groups have been found by classical microbiological screening as for the microbial oxidation of prochiral 2-methyl-l,3-propandiol to (R)-3-hydroxy-2-methyl propionic acid with A. pasteurianus with 97% e.e. and 100% molar conversion [113],... 

A transformation of some synthetic versatility is the oxidation of methyl groups in a methylcobaltocenium salt by Mn04 to give the respective carboxylic acid. In this way, mono- and dicarboxylatocobaltocenium salts have been prepared. These acids can be further functionalized and used as receptors for the selective recognition of anion guest species. A pyrrole-fimctionalized cobaltocenium salt has also been electropolymerized on an electrode surface this system displays anion sensing in solution and when immobilized. ... 

The oxidation of methyl groups of aromatic compounds by CuO-NaOH has been found to be ineffective. Therefore, relatively large amounts of methyl-substituted phenolic and benzene carboxylic acids were isolated from the coal oxidation. 

Selective oxidation of methyl groups can be achieved by platinum salts in aqueous solution. Thus, p-toluenesulfonic acid is oxidized to the alcohol and then to the aldehyde by the Pt(II)/Pt(IV) system. Likewise the methyl group of ethanol can be oxidized without affecting the hydroxyl group [208]. Potassium or sodium bromate in the presence of cerium ammonium nitrate in a water/di-oxane (2 3) mixture can oxidize toluene into a 1 1 mixture of benzaldehyde and benzoic acid. Ethylbenzenes yielded acetophenones [209]. 

The decreasing molecular weight cannot be explained by the oxidation of methyl groups alone since this does not result in chain scission. Some other mechanism must account for the chain scission. 

Note Reagents for TM 2.15a and 2.15b are available aromatic compounds, products of the petrochemical industry. Para-nitrobenzoic acid is produced by nitration of toluene to para-isomer as the prevailing product, followed by oxidation of methyl to the carboxylic group. Orf/m-dimethoxybenzene is produced from ort/to-diphenol, which in turn is available by oxidation of phenol. One technological process uses hydrogen peroxide as oxidant [25], and annual production of ort/io-diphenol reaches 20,000 tons/year, mainly intended for the production of pesticides and perfumes. 

While formic acid accumulation in folic deficiency makes it clear that the main route for formate removal is folic-mediated, little is known in this respect about formaldehyde, which arises from the oxidation of methyl groups or the folic-mediated reduction of formate (Section II, 5). Perhaps an important connection between Ci and the principal pathways for substrates is indicated by the finding that HCHO is an excellent acceptor for the ketol group ( active glycolaldehyde ) formed from a variety of ketose phosphates and from hydroxypyruvate (Dickens and Williamson, 1958). This reaction may be formulated as follows ... 

This is still a very small group. The original member, methyl ivorensate (57), is found in small amount in Khaya ivorensis 14) and was synthesised by oxidation of methyl angolensate with perbenzoic acid (75). It has... 

The ESC A spectra of poly(2,6-dimethyl-l,4-phenylene oxide) photo-oxidized in oxygen are shown in Fig. 4.3. The increase in the intensity of the Oj, band with duration of photo-oxidation is accompanied by the appearance of an envelope of peaks to the high binding energy side of the main Cjj peak [585, 1701], Greater photo-oxidation of the surface can be explained by intensive oxidation of methyl group in poly(2,6-dimethyl-l,4-phenylene oxide). 

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