Thioethers mercaptans

Recent work ( ) with model organosulphur compounds has shown that at temperatures above 350 C and pressures in excess of 100 atm (1500 psig), the hydrolytic desulphurisation reaction occurs readily with thioethers, mercaptans and other non-thio-phenic types of organosulphur compounds. Thiophene itself is more resistant to this type of reaction but desulphurisation is significant in the 450 - 500 C range. More complex fused ring sulphur containing aromatic structures, can, however, be more reactive. 

According to the developer, the technology can treat the following organic solvents alcohols, ketones, aromatic hydrocarbons, ethers, esters, aldehydes, carboxylic acids, thioethers, mercaptans, and amines. 

However, more recent experiments of V. Macho [135,136] and L. Marko et al, [137-144, 829, 913, 953-955] showed that these assumptions have to be corrected. They proved that some sulfur compounds (e.g. saturated thioethers and thiophene) are practically of no harm to the hydroformylation, but that other compounds (e. g. COS, HgS, unsaturated thioethers, mercaptans, mercaptals, disulfides, CSg and elementary sulfur) inhibit the 0X0 reaction by forming sulfur-containing cobalt carbonyls which are inactive as oxo catalysts and less soluble than carbonyls. In the course... 

Mercaptans RSH (also thioethers or sulphides R SR and disulphides R SSR") are generally hquids and possess unpleasant odours. 

Alkyl (or Aryl) 2 4-dinitrophenyl-sulphides (or thioethers) and the corresponding sulphones. Mercaptans react with 2 4-dinitrochlorobenzene in alkaline solution to yield crystalhne thioethers (2 4-dinitrophenyl-sulphides) (I) ... 

Preparation of 2 4-dinitrophenyl-sulphides. Dissolve about 0-5 g. (or 0 005 mol) of the mercaptan in 10-15 ml, of rectified spirit (or in the minimum volume necessary for solution warming is permissible) and add 2 ml. of 10 per cent, sodium hydroxide solution. Mix the resulting sodium mercaptide solution with a solution of 1 g. of 2 4-dinitrochlorobenzene in 5 ml. of rectified spirit. Reaction may occur immediately with precipitation of the thioether. In any case reflux the mixture for 10 minutes on a water bath in order to ensure the completeness of the reaction. Filter the hot solution rapidly allow the solution to cool when the sulphide will crystaUise out. RecrystaUise from alcohol. 

The following classes of sulphur compounds occur in Solubility Groups II, III and VII sulphonic acids and derivatives, ArSO,OR sulphinic acids and derivatives, ArSOOR mercaptans, RSH thiophenols, ArSH sulphides or thioethers, RSR disulphides, RSSR sulphoxides, RR S->0 ... 

Mercaptans and thiophenols (thiols). The thiols are generally liquids with penetrating and disagreeable odours, which persist even at extremely low concentrations in the air. They are soluble in dilute sodium hydroxide solution. Thiols are best characterised as the crystalline 2 4-dinitrophenyl thioethers or as the corresponding sulphones (see Section 111,168). 

The reaction of aliphatic and aromatic mercaptans with aziridines yields thioethers (117—119). 

Mercaptans, thioethers, and disulfides are readily oxidized by ozone. 

Two of the more recendy developed polysulftde polymers are the mercaptan-terminated polyoxypropylene urethane polymer and the polythioether polymer. The urethane-backbone-based polymer is used in many sealant formulations for insulating glass appHcations. The thioether backbone contains sulfur, but no S—S bonds, which are the weakest part of the conventional polysulftde polymer. This polymer improves the thermal stabiHty and reduces the gas—Hquid permeabiHty. 

Substituents attached to a heterocyclic ring through a sulfur atom exist in wider variety than those through oxygen. Besides the simple thio analogues—the thiols (mercaptans), thioethers, thioesters and the like—they include compounds of various higher oxidation states of sulfur, including sulfoxides, sulfones, sulfinic and sulfonic acids and their derivatives. 

The preparation of thiols by S ,2 attack of nucleophilic HS on an alkyl halide gives poor yields because the mercaptan loses a proton to form an anion, RS, which reacts with a second molecule of alkyl halide to form a thioether. 

The aiyl sulfides 424 are prepared by the Pd-catalyzed reaction of aryl halides with the mercaptans 423 or thiophenol 425 in DMSO [209]. Pd(OAc)2 BINAP is active for the reaction of aryl triflates in the presence of t-BuONa [209a], The NiBr2 complex of bipyridine is an active catalyst for thioarylation of aryl iodides with the thiophenol 425, to give diaryl thioether 426 [210],... 

The Leuckart Thiophenol Reaction allows the preparation of thiophenols and corresponding thioethers from anilines or their corresponding diazonium salts. The first step is the reaction of an aryl diazonium salt with a potassium alkyl xanthate to give an aryl xanthate, which affords an aryl mercaptan upon basic hydrolysis or an aryl thioether upon warming. 

Kavcics results on the forms of organic sulfur were confirmed by Ignasiak et al. (7), who determined that about one third of the sulfur in Rasa coal is in thioether links. This result was determined using two independent techniques. Ignasiak et al. also concluded that mercaptanic sulfur was absent from Rasa coal because unspecified chemical tests failed to reveal its presence. 

Sulfur compounds I, II and IV, methyl sulfonic acid, ethylsulfonic acid and benzenesulfonic acid could have been derived from a number of precursors in the parent coal samples. Firstly, mercaptans and thiols will form sulfonic acids when oxidized with peroxides. However, the presence of methylmercaptan, ethylmercaptan and benzenethiol in an exhaustively extracted coal sample is highly unlikely and we believe that the sulfonic acids did not arise from these compounds. In addition, there is a possibility that these sulfonic acids may have come from pendant or terminal thioether groups. 

Substitution of alkyl or aryl hydrocarbon groups, such as phenyl and methyl for H on hydrogen sulfide, H2S, leads to a number of different organosulfur thiols (mercaptans, R-SH) and sulfides, also called thioethers (R-S-R). Structural formulas of examples of these compounds are shown in Figure 1.19. 

Aliphatic Mercaptans 3 Heterocyclic Mercaptans 7 Heterocyclic Thioethers 11 Heterocyclic Disulfides 7 Thiophenes 22 Thiazoles 6... 

Contrary to the mass spectra of mercaptans or disulfides, however, the mass spectra of various thioether compounds (e.g. 8, JL 2 and 1 5) show no loss of an acetyl... 

Reaction with mercaptans and dimercaptans (12, 16, 21) proceeds normally to produce the 2-hydroxybenzyl thioether compounds XXV and XXVI. 

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