Disulfide using

Gaseous Effluents. Twenty percent of the carbon disulfide used in xanthation is converted into hydrogen sulfide (or equivalents) by the regeneration reactions. Ninety to 95% of this hydrogen sulfide is recoverable by scmbbers that yield sodium hydrogen sulfide for the tanning or pulp industries, or for conversion back to sulfur. Up to 60% of the carbon disulfide is recyclable by condensation from rich streams, but costly carbon-bed... 

Metal Ion-Promoted Reactions of Thiols. Metal ion-promoted reactions of thiols have been reviewed (53). The bulk of the coverage concerns metal ion promoted aspects of sulfur chemistry. The main topics of interest are the formation of sulfenamides, sulfides, and disulfides using metal-mediated reactions. 

Bender A continuous process for oxidizing mercaptans in petroleum fractions to disulfides, using a lead sulfide catalyst in a fixed bed. Developed and licensed by Petrolite Corp. 98 units were operating in 1990. 

Locap A process for removing mercaptans from gasoline by catalytic oxidation to disulfides, using a fixed bed of catalyst that is continuously treated with aqueous sodium sulfide. Commercialized by Petrolite Corporation in 1963. 

Merox [Mercaptan oxidation] A process for removing mercaptans from petroleum fractions by extracting them into aqueous sodium hydroxide and then catalytically oxidizing them to disulfides using air. The catalyst is an organometallic compound, either a vanadium phthalocyanine supported on charcoal, or a sulfonated cobalt phthalocyanine. Developed by UOP in 1958 and widely licensed by 1994, more than 1,500 units had been built, worldwide. Unzelman, G. H. and Wolf, C. J., in Petroleum Processing Handbook, Bland, W. F. and Davidson, R. L., Eds., McGraw-Hill, New York, 1967, 3-128. 

Disulfiram [bis(diethylthiocarbamoyl)disulfide] used in the treatment of alcoholism can be assayed directly by pulse polarography in an aliquot of a solution of a ground tablet dissolved in ethanol-acetate buffer (pH 4.5) [133]. A mechanism for the electrode process was proposed involving the reaction of the disulfiram with the mercury drop to form an insoluble mercuric salt, which then underwent reduction at the electrode surface. 

Sulfide Samples. The tert-butyl sulfide and the tert-butyl disulfide used in these experiments were obtained from the Aldrich Chemical Co. The purity of the monosulfide (MW 146.30) was in excess of 97%. The technical grade disulfide (MW 178.36) was 38% pure and contained 62% tertiary butyl trisulfide. 

The quality of the product depends to a large extent upon the purity of the tetraethylthiuram disulfide used. Since the yield is decreased in proportion to the quantity of water present, reagents used should be dry. Dry Sharpies Tetraethylthiuram Disulfide No. 163 was found to be satisfactory without further purification. 

The well-known instability of the disulfide anion radicals, (R SR2)-, is apparently explained by the antibonding electron population, presumably in the framework of the disulfide bond. In some cases, however, these anion radicals turned out to be more or less stable (Breitzer et al. 2001). Two examples in Schemes 3-22 and 3-23 deserve to be distinguished. Firstly, one-electron reduction of naphthalene-1,8-disulfide using sodium in dimethoxyethane generates the corresponding anion radical, Scheme 3-22. Second, the oxidation of a [l,n]-dithiol by Ti(III)-H202 at pH 7 produces the cyclic disulfide according to Scheme 3-23 ... 

Table 3.3 Synthesis of disulfides using Clayfen-type oxidants.

Doctor sweetening a process for sweetening gasoline, solvents, and kerosene by converting mercaptans to disulfides using sodium plumbite and sulfur. 

D. Bhar and S. Chandrasekaran, A simple synthesis of sugar disulfides using tetrathiomolyb-date as a sulfur-transfer reagent, Carbohydr. Res., 301 (1997) 221-224. 

Cellulose xanthate, or more exactly, sodium cellulose xanthate or sodium cellulose dithiocar-bonate, is obtained by mixing the aged soda cellulose with carbon disulfide in a vapor-tight xanthating chum. Based upon weight of cellulose, the amount of carbon disulfide used will be in the range of 30 percent for regular rayon to 50-60 percent for modified varieties. 

Similarly, Lagercrantz and coworkers (232) have used organic nitroso compounds as "spin traps," and Leaver and coworkers (233) studied nitroxides formed during photo-lyses of indoles, phenols, thiols, and disulfides using... 

Bis(4-fluorophcnyl) disulfide (3.49 g, 13.72 mmol), CF,CO,K (4.107 g, 27 mmol), and sulfolane (3mL) were added to a flask for distillation, and immersed into a preheated oil bath (180 C). The heterogeneous mi.xture quickly solubilized, and was then rapidly heated to 230 C with stirring. Soon, 4-fluorophcnyl trifluoromethyl sulfide began to distill, and was collected in the receiving flask (the reaction was complete within 10 min). The crude product contained ca. 3 wt% sulfolane. Redistillation afforded the analytically pure sulfide yield 2.2 g (82%, based on the disulfide used). 

Caution Carbon disulfide, used as a solvent in this preparation, is highly inflammable its vapor may ignite on contact with a hot laboratory steam line. 

Any mercaptans boiling below 80°C are also readily dissolved in alkaline solutions (Eq. 18.32). A common process for the removal of dissolved mercaptans of this kind, especially from catalytically cracked gasoline and liquefied petroleum gas, is the Universal Oil Products (UOP) Merox process that also uses caustic soda for extraction. In this process, however, the mercaptans are then oxidized to disulfides using air assisted by a metal complex catalyst dissolved in the caustic soda (Eq. 18.34). 

Figure 7.2 Aromatic thiols and disulfides used in this work for the monolayer formation.

The yield of dimethylphosphine can be increased by increasing the amount of tributylphosphine which allows use of water in the less volatile form of a hydrate. Thus using the same apparatus, procedure and with the same amount of tetramethyldiphosphine disulfide, using 50.5 g (250mmole) P(n-C4H9)3 and 15.2 g (80mmole) p-toluenesulfonic acid hydrate, the yield of dimethylphosphine is 7.1 g (95%). 

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