Methane thiol, reaction

Figure 3 SC BO emission spectra obtained in the reaction of methane thiol with 03 at 620 mtorr in He (a) 9 mtorr 03, 3 mtorr CH3SH (b) 15 mtorr 03, 7 mtorr CH3SH (c) 20 mtorr 03, 7 mtorr CH3SH (d) 30 mtorr 03, 15 mtorr CH3SH. (Reprinted with permission from Ref. 27. Copyright 1981 American Chemical Society.)...

The chemiluminescent reaction with chlorine dioxide provides a highly sensitive and highly selective method for only two sulfur compounds, hydrogen sulfide and methane thiol [81]. As in the flame photometric detector (FPD), discussed below, atomic sulfur emission, S2(B3S -> ) is monitored in the wave-... 

EH s that are often encountered in sediment pore waters. Cores from Mono ake (not shown) had extremely alkaline pH s of 9.8 to 10.1. This high a pH definitely has an effect on the bimane reaction. Pore water samples adjusted to pH 8 gave much higher results which were similar to those obtained from the methylene blue and DTNB method (data not shown). Thiosulfate and sulfite were present in micromolar quantities in cores from all habitats. Thiosulfate was highest in the salt pond cores where it occasionally was more abundant than sulfide. While methane thiol, glutathione, and other organic thiols can be detected by the bimane method, they were not abundant (< 10 mM) in the core samples we chose to analyze. 

Fig. 4.14. The Chugaev reaction for the dehydration of alcohols. (The decomposition of dithiocarbonic acid methylester—here given in brackets—to form carbon oxy-sulfide and methane thiol is outlined in Section 8.1 near Figure 8.4.)...

Methane thiol oxidizes at a convenient rate at 200—275 °C, the reaction being mildly autocatalytic and accompanied by a pressure decrease [107]. The rate is enhanced by increased oxygen concentration, but retarded by excess thiol. The main products include sulphur dioxide, carbon monoxide, formaldehyde, acetaldehyde and methane but no hydrogen sulphide, carbonyl sulphide or free sulphur. Unless excess oxygen is present, these products do not account for all the sulphur consumed, and Cullis and Roselaar [107] attributed this to formation of dimethyl disulphide although later work [108] has shown that this explanation was unlikely. 

The combustion of dimethyl disulphide was studied at 240 °C. The reaction is autocatalytic, the principal products being sulphur dioxide, methanol and carbon monoxide with smaller amounts of formaldehyde, methane thiol and an acid [111]. 

Take, for example, the reaction of methanol or methane thiol with proto-nated thiolacetic acid (Scheme II). The observed product of acyl transfer is II corresponding to loss of H2S. If II is formed by way of an addition intermediate, then formation of the intermediate by an independent route should give the same product II. However, reaction of the thionic ester III with water failed to give II or any product that could be ascribed to the intervention of a tetrahedral addition intermediate I (15). 

Scheme 8.69. The Chugaev reaction. The salt of an alcohol is allowed to react with carbon disulfide, producing the sodium salt of a dithiocarbonate derivative, which, on Sn2 reaction with methyl iodide (CH3I), produces the corresponding xanthate ester. Heating the xanthate (pyrolysis) results in loss of carbon oxysulfide (COS), methane thiol (thiomethane), and the corresponding alkene.

Alkylation and Arylation. The 5-methylation of thioamides by diazomethane is catalysed by silica gel. 5-Phenyl derivatives of thiobenzanilides are obtained in high yield by radical arylation with nitrosoacetanilide or phenylazotriphenyl-methane. Thiols are made from alkyl (or cycloalkyl, or aralkyl) halides by their reaction with dimethylthioformamide and treatment of the imidium ester with methanol other methods of hydrolysis lead to side-reactions, giving impure products. Mono- and bi-protic thiocarboxamides condense with ethyl bromo-cyanoacetate and one equivalent of NaOEt with spontaneous separation of sulphur and the formation of ff-amino-cr-cyano-acrylates, as shown in reaction (5). The... 

Catalytic hydrogenation with platinum liberates the hydrocarbon from methylcobalamin (57) and from alkyl-Co-DMG complexes (161), but not from pentacyanides with primary alkyl, vinyl, or benzyl ligands, though the cr-allyl complex yields propylene (109). Sodium sand gives mixtures of hydrocarbons with the alkyl-Co-salen complexes (64). Dithioerythritol will liberate methane from a variety of methyl complexes [cobalamin, DMG, DMG-BF2, G, DPG, CHD, salen, and (DO)(DOH)pn] (156), as will 1,4-butanedithiol from the DMG complex (157), and certain unspecified thiols will reduce DMG complexes with substituted alkyl ligands (e.g., C0-CH2COOH ->CH3C00H) (163, 164). Reaction with thiols can also lead to the formation of thioethers (see Section C,3). 

Tucci and Holm [163] have demonstrated an alternative reaction scheme, starting from the complex [NIi(bpy)(CH3)2(SR")2], where bpy is 2,2 -bipyridyl and R" is aromatic. In this case, the thiol displaced one methyl group from the nickel as methane, in a reaction reminiscent of methyl-CoM reductase, and coordinated to the nickel. Further addition of CO liberated CH3COSR" in high yield. This reaction demonstrates the feasibility of a reaction in which both the thiol and acetyl groups coordinate the nickel. 

Although only a few hydrocarbons have been studied it appears that most of them react with OH with a rate constant of ca. 109 M-1 s 1. Methane is about 4 times less reactive than this value, and cyclopentane and cyclohexane about 5 times more reactive. Alcohols, amines, ethers, and many esters also fall in the same range. Carboxylic acids and carbonyl compounds seems to be to a certain degree less reactive. Lower reactivity is also found for the protonated forms of amines and amino acids. Direct reaction of OH with the substituent is usually unimportant except for a few cases such as thiols, where H is easily abstracted from the SH, or nitroso com-... 

A mild procedure for the appendage of MOM groups to acid-sensitive substrates is illustrated by the protection of the allylic alcohol in Avermectin derivative 259.1 using [(methoxymethyl)thio]-2-pyridine (259 2) sitver(I) Inflate and sodium acetate in THF at room temperature [Scheme 4.259],479 Primary secondary and tertiary alcohols and phenols are methoxymethylated in good yield though phenols are slower to react. Reagent 259.2 (bp 66 °C/0.088 kPa) is easily prepared in 75% yield by the reaction of pyridine-2-thiol with dimethoxy-methane activated by trifluoroborane etherate. 

CoM, because the purified methyl reductase in methanogens is specific for methyl CoM and not methylcobalamin. It appears that methylcobalamin reacts with coenzyme M, 2-mercaptoethanesul-fonic acid, to give methylcoenzyme M in a reaction catalyzed by a methyltransferase enzyme. Finally, the methyl CoM is reduced to give methane (equations 41 and 42). It is noteworthy that methylcobalamin once more reacts with a thiol. The methyl coenzyme M reductase which catalyzes reaction (42) has a nickel-containing prosthetic group, factor F430, which is discussed in Section 62.1.7.2. 

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