Mercaptans, alkylation oxidation

There are several oxidation reactions effected by NO that can be incorporated into the BNO scheme. Mercaptans are oxidized to symmetrical disulfides 22), triphenylphosphine to triphenylphosphine oxide, and phosphites to phosphates (18,22), A kinetic study (18) of the reaction of alkyl phosphites with nitric oxide indicates that the reaction is first-order in phosphite and first-order in nitric oxide. This indicates initial formation of a species, BNO ... 

S Alkylation s. Thioethers from mercaptans Alkylene oxides s. Oxido compds. 

Mercaptides are unchallenged as the ligand of choice for the other entities bonded to the tin, but carboxylates can also be used. Whereas a variety of mercaptans are used, the thioglycolic acid derivatives remain the largest single mercaptan. Dibutyltin bis(isooctyl thioglycolate) [25168-24-5] and butyltin tris(isooctyl thioglycolate) [25852-70A] are two common examples. These materials are produced by the reaction of the appropriate alkyl tin chloride or oxide, and the mercaptan. 

Nonionic Surface-Active Agents. Approximately 14% of the ethyleae oxide consumed ia the United States is used in the manufacture of nonionic surfactants. These are derived by addition of ethylene oxide to fatty alcohols, alkylphenols (qv), tall oil, alkyl mercaptans, and various polyols such as poly(propylene glycol), sorbitol, mannitol, and cellulose. They are used in household detergent formulations, industrial surfactant appHcations, in emulsion polymeri2ation, textiles, paper manufacturing and recycling, and for many other appHcations (281). 

Sulfuric acid treatment. In this treatment, oxidation ofmercaptans occurs. If alkyl radical in mercaptans is denoted by R, the reaction can be described as shown below ... 

Suitable collectors can render hydrophilic minerals such as silicas or hydroxides hydrophobic. An ideal collector is a substance that attaches with the help of a functional group to the solid (mineral) surface often by ligand exchange or electrostatic interaction, and exposes hydrophobic groups toward the water. Thus, amphi-patic substances (see Chapter 4.5), such as alkyl compounds with C to C18 chains are widely used with carboxylates, or amine polar heads. Surfactants that form hemicelles on the surface are also suitable. For sulfide minerals mercaptanes, monothiocarbonates and dithiophosphates are used as collectors. Xanthates or their oxidation products, dixanthogen (R - O - C - S -)2 are used as collectors for... 

In addition to the alkylated phenol mentioned, the hydrophobic part of the molecule may be derived from the fatty acids resulting from wax oxidation, and mercaptans from... 

The reaction of OPA with amino acids (see Fig. 10) requires a mercaptan cofactor that is incorporated as part of the final derivative product. The choice of mercaptan can affect derivative stability and chromatographic selectivity (178). Mercaptoethanol is the most commonly used coreagent. Cysteine is not well detected, because this amino acid can react at the a-amine group or it can react via the side chain thiol. Thus, cysteine is determined only after conversion of the thiol group by oxidation or alkylation. Reaction time with OPA is very fast, 1 minute at room temperature. Detection limits are typically in the low picomole range. Representative references include... 

Alkyl sulfides and thiols. Some alkyl thiols and sulfides, notably those from commonly ingested Allium sativum (garlic) and Allium cepa (onion) (Alliaceae), are variously bioactive as odorants and antimicrobials. Propanethial S-oxide (CH3-CH2-CH=S=0) is a lachrymatory irritant principle of onion. Allicin (S-oxodiallydisulfide CH2=CH—CH2-SO-S-CH2— CH=CH2), diallyldisulfide (CH2=CH-CH2-S-S-CH2-CH=CH2) and diallylsulfide (CH2=CH—CH2—S—CH2-CH=CH2) are major odorants of garlic that are reactive and irritant because of the allyl groups. Dimethyl disulfide (CH3—S—S-CH3), dipropyl disulfide (CH3-CH2-CH2-S-S-CH2-CH2-CH3), methyl allyl disulfide (CH3-S-S-CH2-CH=CH2) and propane-1-thiol (CH3-CH2—CH2—SH) are further Allium odorants. Methane thiol (methyl mercaptan CH3—SH) is a widespread plant volatile and notably derives from anaerobic bacterial degradation of cysteine as in human flatus and bad mouth odour. The aliphatic disulfides allicin and ajoene inhibit proinflammatory expression of iNOS. 

Ethylene oxide reacts with hydrogen sulfide at 45-60° to produce -hydroxyethyl sulfide in 90% yield. The reaction can be stopped at the mercaptan stage with excess hydrogen sulfide. Analogous reactions of ethylenimine and ethylene sulfide produce both the sulfides and substituted mercaptans. Cleavage of the ethylene oxide ring by mercaptans gives /S-hydroxyethyl alkyl sulfides in 70-90% yields. ... 

ALKYLATION Benzyltiiethylammonium chloride. n-Butyl mercaptan. Dialkylcar-bonium fluoroborates. Diethoxycarboni-um fluoroborate. Dimethylcopperlithium. Ethyl vinyl ether. Dimethylformamidc dimethyl acetal. Dimethyl sulflde. Dimeth-ylsulfonium methylide. Ethyl chlorofor-mate. Hexamethylphosphoric tiiamide. Lithium diisopropylamide. Lithium N-iso-propylcyclohexylamide. O-Methyldiben-zofuranium fluoroborate. Methyl fluoro-sulfonatc. Naththalene-Sodium. Palladi-um(II) chloride. 1,2,2,6,6-PentamelhyI-pipetidine. Potassium hydroxide. Silver oxide. Sodium bis-2-mcthoxyethoxyaIu-minum hydride. Sodium hydride. Thai-lous ethoxide. 

Oxidations by chlorine are limited to only few types of compounds. In organic solvents and pyridine [681] or hexamethylphosphoramide (HMPA) [682] as cosolvents, primary alcohols are oxidized to aldehydes and secondary alcohols to ketones [681, 682]. Secondary alcohols are oxidized in preference to primary alcohols [681]. Many oxidations with chlorine are carried out in aqueous media and involve sulfur-containing compounds. Mercaptans [683], alkyl thiolcarboxylates [683], thiocyanates [684], isothioureas [684], disulfides [655], and sulfinic acids [656] are transformed into sulfonyl chlorides. The chlorination of dimethyl disulfide in acetic anhydride yields methanesulfinyl chloride [657]. 

Removing 02 is necessary for the safe operations of many reactions, especially hydrogenations. Funtional groups which are readily oxidized with 02 include mercaptans, tervalent phosphorus compounds, and some amines. Anions may also react with dissolved 02, leading to the generation of impurities during alkylation of these anions [16]. 

Polyoxyethylene mereaptans, obtained from the reaction between an alkyl mercaptan and ethylene oxide, have been demonstrated to be good nonionic... 

Scheme 1.70. Pro-oxidant activity of alkyl mercaptans (a) and both pro-oxidant and delayed antioxidant activity of diphenyl disulfides (b) during melt processing of polymer PH containing hydroperoxide groups POOH. After Scott (1993b).

Another set of tribenzotriquinacenes functionalized at the peripheral bridgehead positions is shown in Scheme 32. The triamines 162 and 163 were obtained in excellent yield by aminolysis of the methyltribenzotriquinacene 142 with ammonia and dimethylamine, respectively, in benzene solution [100]. Solvolysis of 142 in the neat alkyl (R = Me, Et, Pr, nBu) and benzyl mercaptane gave the three-fold thioethers 164 and 165 [106]. Oxidation of these compounds with raeta-chloroperbenzoic acid (MCPBA) led to complete decomposition [98], whereas use of dimethyldioxirane gave high yields of the tris(sulfones) 166 and 167 as thermally stable compounds [106]. 1H- and 13C-NMR spectrometry as well as X-ray structural analysis revealed the dynamic behaviour of the sulfones,... 

Alkyl Bound to Miscellaneous Elements. Several compounds in which alkyl is bound to a sulfur atom have become quite important in recent years for example, the mercaptans, such as amyl and ethyl mercaptan, are used as warning agents in natural gas because of their intense and disagreeable odor. Mercaptans are also employed in organic syntheses as, for instance, the manufacture of sulfonal by the condensation of ethyl mercaptan (ethanethiol) with acetone, followed by oxidation. In recent years a very considerable amount of mercaptan has been used for controlling the polymerization reaction between butadiene and styrene to form synthetic rubber (GR-S). 

Sulphur Compounds.—Mercaptans form salts by the replacement of one hydrogen atom by metals. Sulphides do not form salts they yield sulphoxides and sulphones on oxidation. Sulphates of amines give a precipitate of barium sulphate with barium chloride. The alkyl sulphates yield inorganic sulphates on hydrolysis. The sulphonic acids are not hydrolyzed by bases. 

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