Methanol and Formate

2 Methanol and Formate. - Methanol intoxication can result from both accidental and deliberate ingestion. The alcohol undergoes ADH-catalysed oxidation to formaldehyde, which is then rapidly metabolised to formic add, resulting in metabolic acidosis. 

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Methylotrophs Microbes that use single-carbon compounds, such as methanol and formate, as electron donors. 

After discussing the dehydration of methanol and formation of DME, we are able to illustrate a number of key theoretical concepts. The first is that carbocation fragments are found in transition states, rather than as stable intermediates. Furthermore, the nature of these species is different from what is predicted from gas-phase studies, experimental or theoretical. The cluster, i.e., the zeolite, controls the stabilization of this carbocationic fragment. Second, we see that each different reaction requires a different transition state, rather than formation of a transition state that can be converted in a number of possible reactions. (This latter view received some support as a result of different processes possessing very similar activation barriers.)... 

Hydrate Reservoir fluid with methanol and formation water Reference Ng and Robinson (1994)... 

Hemodialysis rapidly eliminates both methanol and formate. However, ethanol will also be eliminated in the dialysate, requiring alterations in the dose of ethanol. Hemodialysis is discussed in Chapter 59 Management of the Poisoned Patient. 

An interesting variation on the methanol formation is that in some cases higher oxygenates can be formed (e.g., ethanol, acetic acid or isobutanol), over mixed oxides (such as Zr02/Zn0/Mn0/K20/Pd) or promoted copper catalysts. These are probably secondary products derived from methanol and formate by more standard organic reactions. 

Hemodialysis corrects any metabolic acidosis while removing methanol and formate [97] and should be considered with evidence of organ toxicity, presence of acidosis, and methanol levels greater than 50 mg/ dL. Fomepizole is dialyzable (see next section). Closure of the osmolal gap correlates with methanol removal and can be followed if methanol levels are unavailable or... 

Hovda KE, Andersson KS, Urdal P, et al. Methanol and formate kinetics during treatment with fomepizole. Clin Toxicol (Phila). 2005 43 221-227... 

The conversion of a dimeric rr-bound methyl propargyl ether complex [Mo2(CO)4Cp2(At-Tj, i7--CH=CCH20Me)] (35) to the cationic allenyl complex [Mo2(CO)4Cp2(m-i7% i -CH=C=CH2] (36) has been described by Curtis et al. (25). Protonation of 35 with HBF4 induced the loss of methanol and formation of the required complex. Alternatively the same complex was reported accessible via the acid-promoted elimination of methanol from [Mo2(CO)4Cp2 M-T7%Tj -MeO(H)C=C=CH2 ], a rare example of an intact T7%Tj -bound allene (Scheme 9). 

The Cannizzaro reaction of formaldehyde is far from a simple kinetic process that could be characterized by first- or second-order kinetics, and that would be a single reaction in which methanol and formate are produced. Rather, it proceeds in alkaline medium in conjunction with the formose reaction, the autocatalytic self-addition of formaldehyde to produce glycolaldehyde, which is then followed by aldol reaction to afford higher aldoses and ketoses. Mono-, di-, tri-, and tetra-valent bases, as well as nitrogenous bases, have been reported to catalyze both reactions homo-... 

Hemodialysis is effective in removing methanol and formate and in correcting severe metabolic acidosis. Indications for hemodialysis include severe acidosis or osmolar gap (see p 32) greater than 10 mOsm/L. 

One of the liberated alcohols attacks the protonated carbonyl of the methyl ester, producing the elimination of methanol and formation of a 6-lactone. 

Unstable in aqueous media, generation of BCM (see Section 9.4) at pH > 13 quantitative conversion to 3-butyl-2,4-dioxo-s-triazino[l,2-a] benzimidazole (STB) (Chiba Singh, 1986) decomposition when heated (release of methanol and formation of STB — see Section 9.5.1)... 

The removal and use of one-carbon units from folate Single-carbon units are removed from folate by a number of reactions. The enzyme 10-formylTHF dehydrogenase provides a mechanism for disposing of excess one-carbon units as carbon dioxide. (Folate administration to animals enhances the conversion of ingested methanol and formate to carbon dioxide, diminishing methanol toxicity.) Additionally, singlecarbon units from 10-formylTHF are used for the biosynthesis of purines (Figure 2). 

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