Methanol degradation

What is the metabolic pathway of methanol degradation How does this result in acidosis ... 

Three primary photochemical reactions contribute to the overall mechanism of methanol degradation depending strongly on the special reaction conditions, i.e. on the initial concentration of methanol and on molecular oxygen saturation of the aqueous phase ... 

Reactions with Organic Compounds. Tetrafluoroethylene and OF2 react spontaneously to form C2F and COF2. Ethylene and OF2 may react explosively, but under controlled conditions monofluoroethane and 1,2-difluoroethane can be recovered (33). Benzene is oxidized to quinone and hydroquinone by OF2. Methanol and ethanol are oxidized at room temperature (4). Organic amines are extensively degraded by OF2 at room temperature, but primary aHphatic amines in a fluorocarbon solvent at —42°C are smoothly oxidized to the corresponding nitroso compounds (34). 

Arabinan. This highly soluble polymer is found in the extracts of many fmits and seeds, in the boiling water extracts of pine wood (127), in the extracts of marshmallow roots (A/t/jaea officina/is) (128), and aspen (63) and willow (Sa/ix a/ba F) (129) bark. Because arabinan can be isolated from mildly degraded pectin fractions, it is often difficult to determine whether it is a hemiceUulose or a labile fragment of a larger polysaccharide and/or lignin complex. Arabinans have a complex stmcture composed almost entirely of 5-linked a-L-arabinofuranosyl units with similar residues linked to them at C-2 and/or C-3 and is soluble in 70% aqueous methanol solution. 

Stannous Sulfate. Stannous sulfate (tin(Il) sulfate), mol wt 214.75, SnSO, is a white crystalline powder which decomposes above 360°C. Because of internal redox reactions and a residue of acid moisture, the commercial product tends to discolor and degrade at ca 60°C. It is soluble in concentrated sulfuric acid and in water (330 g/L at 25°C). The solubihty in sulfuric acid solutions decreases as the concentration of free sulfuric acid increases. Stannous sulfate can be prepared from the reaction of excess sulfuric acid (specific gravity 1.53) and granulated tin for several days at 100°C until the reaction has ceased. Stannous sulfate is extracted with water and the aqueous solution evaporates in vacuo. Methanol is used to remove excess acid. It is also prepared by reaction of stannous oxide and sulfuric acid and by the direct electrolysis of high grade tin metal in sulfuric acid solutions of moderate strength in cells with anion-exchange membranes (36). 

This has a very high resistance to impact damage, even at subzero temperatures. It has good creep strength in dry conditions up to 115°C but degrades by continuous exposures to water hotter than 65°C. It is resistant to aqueous solutions of acids, aliphatic hydrocarbons, paraffins, alcohols (except methanol), animal and vegetable fats and oils, but is attacked by alkalis, ammonia, aromatic and chlorinated hydrocarbons. 

Periodic Acid Degradation 17a,20 -Dihydroxy-4,4,6,16a-tetramethyl-pregn-5-en-3-one (0.3 g) is dissolved in 30 ml of methanol and treated with an aqueous solution of 0.25 g of periodic acid in 5 ml of water at room temperature for 17 hr. On dilution with water, the resultant crystals are collected by filtration, washed well with water, and dried to give 0.26 g mp 158-160°. Recrystallization from hexane-acetone gives 0.24 g (90%) of 4,4,6,16a-tetramethylandrost-5-ene-3,17-dione mp 160-161° [aj —6° (CHCI3). 

Similarly, photooxidation of dihydrocoralyne (108) in hot methanol at pH 8, subsequent addition of sodium methoxide and additional irradiation yielded 6,7-dimethoxyisoquinolone and 3-methyl-3,5,6-trimetho-xyphthalide via the betainic intermediate 109 (77H45) (Scheme 39). It was demonstrated earlier that dihydrocoralyne is oxidized to this betaine in quantitative yields under physiological conditions (76H153). The autoox-idative degradation of the mesomeric betaine was rationalized by the addition of singlet oxygen. 

Oxidation of ecgonine (2) by means of chromium trioxide was found to afford a keto acid (3). This was formulated as shown based on the fact that the compound undergoes ready themnal decarboxylation to tropinone (4)The latter had been obtained earlier from degradative studies in connection with the structural determination of atropine (5) and its structure established independently. Confirmation for the structure came from the finding that carbonation of the enolate of tropinone does in fact lead back to ecgonine. Reduction, esterification with methanol followed by benzoylation then affords cocaine. 

In this oxidative degradation, MTO decomposes into catalytically inert perrhenate and methanol. The decomposition reaction is accelerated at higher pH, presumably through the reaction between the more potent nucleophile H02- and MTO. The decomposition of MTO under basic conditions is rather problematic, since the selectivity for epoxide formation certainly profits from the use of nonacidic conditions. 

Methanol is a very minor product and the observation that its polarization is more intense in N20-saturated solution than in He-saturated solution suggests that it is formed by reaction of OH" radical, probably by a degradation of the radical formed by the addition of OH to DMSO other than the main one given in reaction 21. 

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