Quenching carbon disulfide

Carbon disulfide quenches the fluorescence of anthracene quite efficiently,145,149 but seems to have little effect on its triplet lifetime.147 Diphenylanthracene in benzene fluoresces with a quantum yield of 0.8 and shows a high sensitivity to the oxygen concentration in photooxygenation reactions. With about 1 vol% of CS2 present, AC>2 is practically independent of [02] (> 10"5 mole/liter). In jjoth cases, where carbon disulfide was either used as solvent or was added to an otherwise strongly fluorescent solution, the quantum yields of photooxygenation followed... 

Sulfur-selenium phases can be prepared by cooling molten mixtures of the elements either slowly or by quenching followed by extraction with carbon disulfide, carbon tetrachloride or benzene. The crystals are obtained upon evaporation or cooling of the resulting solutions. Their colour deepens from yellow to ruby red with increasing selenium content In the older literature there has been some confusion whether to consider these phases as mixed crystals of discrete Sg and SCg molecules or as binary compounds containing SeS bonds. 

The sulfonyl group is a key feature in the preparation of the unusually substituted dithiin sulfone (174) from dibenzyl sulfone. The acidic a-protons are abstracted with sodium hydride and the carbanionic intermediates react with carbon disulfide. The reaction is quenched with methyl iodide to give (174) in 17% yield (73BSF637). Another multisubstituted dithiin (175) is available from the reaction of diphenylthiirene dioxide with the ylide (176) (Scheme 21) but again the yield is low. However, the reaction is of particular interest in so far as the product mixture also contains a derivative of the rare oxathiin nucleus. Indeed of the three products isolated the oxathiin sulfone (177) is formed in marginally the highest yield (73BCJ667). 

The mercury chloride sulfide 7-Hg3S2Cl2 is obtained by either quenching a mixture of mercury(II) sulfide vapor from 750°C. or by the reaction of a dilute alkaline solution of mercury(II) chloride with carbon disulfide. The conditions for the preparation of Hg3S2Cl2 are given in Table IV. 

Thirty-nine different dithiocarbamates have been efficiently prepared through a one-pot reaction of an aliphatic primary or secondary amine, carbon disulfide and an alkyl halide (Figure 2.16). " Typically, all reagents were liquids and the mixture slowly solidified upon reaction. Therefore, although the reaction does not use solvents, the reagents are probably acting as the solvent in this procedure. Additionally, the reactions were quenched with water and extracted with ethyl acetate, so solvent was used. Nevertheless, this is an excellent synthetic method for the preparation of S-alkyl dithiocarbamates, which are useful compounds for the pharmaceutical and agrochemical industries. 

Acid chloride—olefin addition and Friedel-Crafts cyclization A previous procedure was improved by use of methylene chloride as solvent rather than carbon disulfide. To check the progress of the reaction, one can quench a 2 3-ml. aliquot with water in a test tube, separate and dry the organic phase, and evaporate. The infrared spectrum will show disappearance of the acid chloride carbonyl band at 5.6(1 /j and appearance of the... 

After the addition of the tin(IV) chloride-etherate slurry is completed, the reaction mi.xture is allowed to warm slowly (over a period of at least 30 minutes) to —20°. The mixture is then quenched to —78°, and the reaction flask is removed from the vacuum line. The material in the —95° trap (mostly solvent) is discarded. The crude product in the —196° traps is combined and passed four times through a —112° trap (carbon disulfide slush) to remove traces of solvent. This procedure typically gives 0.020 mole (30% yield) of stannane %vith a vapor pressure of 17 mm. at —112°. 

Williams carried out a Julia coupling similar to the Keck example. With the removal of the acetal functionality, the coupling step of the Julia reaction was efficient, but the usual reductive elimination procedure failed. As an alternative to the acetylation and reductive elimination procedure, the P-sulfo-nyl xanthate was formed by quenching the addition reaction with carbon disulfide and methyl iodide. Reductive elimination was then carried out with tri-n-butyltin hydride to yield the desired ( )-alkene (399) in an 85 15 ratio with the (Z)-alkene in 83% overall yield (equation 91). 

To a solution of the P-hydroxy-/V-methyl-O-methylamide (0.272 g, 1.55 mol) in tetrahydrofuran (THF) (30 mL) were added carbon disulfide (6.75 mL, 112 mmol) and iodomethane (6.70 mL, 108 mmol) at 0 °C. The mixture was stirred at this temperature for 0.25 h, and then sodium hydride (60% suspension in mineral, 136.3 mg, 3.4 mmol) was added. After 20 min at 0 °C, the reaction was quenched by slow addition to 60 g of crushed ice. (Caution hydrogen gas evolution ). The mixture was raised to room temperature and separated, and the aqueous layer was extracted with CH2CI2 (4x15 mL). The combined organic extracts were dried (Na2SO4), concentrated in vacuo, and purified (SiO2, 5% EtOAc in hexanes) to afford 0.354 g (86%) of the xanthate. To a solution of the xanthatc (2.95 g, 11.1 mmol) in toluene (100 mL) was added tributyltin hydride (15.2 mL, 56.6 mmol) and 2,2 -azobisisobutyronitrilc (AIBN, 0.109 g, 0.664 mmol). The reaction mixture was then heated to reflux for 1 h. The mixture was cooled, concentrated in vacuo, and purified (SiO2, 100% hexanes to remove tin byproducts, followed by 10% EtOAc in hexanes to elute product) to afford 1.69 g (96%) of the/V-methyl-O-methylamide. 

Polymeric sulfur is produced commercially as insoluble sulfur (IS) and is used in the rubber industry [56] for the vulcanization of natural and synthetic rubbers since it avoids the blooming out of sulfur from the rubber mixture as is observed if Ss is used. The polymeric sulfur (trade-name Crys-tex [57]) is produced by quenching hot sulfur vapor in liquid carbon disulfide under pressure, followed by stabilization of the polymer (against spontaneous depolymerization), filtration, and drying in nitrogen gas. Common stabilizers [58] are certain olefins R2C=CH2 like a-methylstyrene which obviously react with the chain-ends (probably -SH) of the sulfur polymer and in this way hinder the formation of rings by a tail-bites-head reaction. In this industrial process the polymer forms from reactive small sulfur molecules present in sulfur vapor [59] which are unstable at ambient temperatures and react to a mixture of Ss and on quenching. 

Quenching of sulfur vapor in a cold solvent like carbon disulfide ( supersublimation product commercially available under the trade-name Crys-tex)... 

If liquid sulfur, after the chemical equilibrium has been established (12 h at 120 C or 1 h at 250 °C), is rapidly quenched to low temperatures and inune-diately extracted with carbon disulfide the polymeric will remain undissolved while Ss and S fWill dissolve. After filtration, most of the Ss will crystallize out on cooling of the solution to -78 C while S together with some Ss remains in solution. It is not possible to isolate S i completely free of Ss-Therefore, in the literature the mixture Ss+S t has often been simply termed S f but in this chapter we will differentiate between S f on the one hand and mixtures of S f with Ss on the other hand ( Ss-I-S r ). If a solution of Ss+S s is evaporated in a vacuum a yellow resin-like mass is obtained which solidifies at low temperatures as a glass but decomposes at room temperature within a few days to a crystalline mixture of Ss and S [19]. 

After equilibration liquid sulfur contains a certain concentration of polymeric molecules (Soo) at all temperatures. This polymer can be isolated and determined by quenching the melt at very low temperatures, extracting the smaller molecules immediately by pure carbon disulfide at 20 °C, and drying the residue of S in a vacuum. Extraction and drying should be done with exclusion of light and nucleophiles and avoiding higher temperatures which would initiate the conversion of the polymer to cyclo-Ss. The content of jx-sulfur thus obtained depends on the purity of the melt. In addition, it has to be obeyed that the r-sulfur present in the quenched melt is unstable at 20 °C and partly polymerizes to S for which reason the extraction has to be done without any delay if the true polymer content of the melt is to be determined. If, on the other hand, simply S is to be prepared it is possible to in-... 

For reasons of completeness it should be pointed out that polymeric sulfur is also obtained if sulfur vapor is quenched from very high temperatures (e.g., 600 °C) to very low temperatures (liquid nitrogen) followed by warming the condensate to -1-20 °C and extraction with carbon disulfide. Up to 60% S have been obtained in this way [53]. Commercially polymeric sulfur (trade name Crystex) is produced by a similar process (see the chapter on Solid Sulfur Allotropes in this volume). The glass transition temperature of Crystex is -1-75 °C [51]. 

Tables Molecular composition of equilibrated liquid sulfur (mass %) after quenching the melt from temperatures of between 116 and 387 °C to -196 °C. is the fraction insoluble in carbon disulfide (polymeric sulfur)... 

To an ice cold mixture of the organic halide (3 mmol) and carbon disulfide (6 mmol) in a test tube was added amine (6 mmol) and the mixture was stirred at 0 °C for 30 min, then warmed to room temperature where stirring was continued until the reaction was complete (reaction mixture solidified or monitored by TLC). The reaction was quenched by addition of water and was extracted with EtOAc, dried over anhydrous Na2S04, and evaporated to give NMR pure product. Further purification in some cases could be achieved by silica gel column chromatography eluted with petroleum ether and ethyl acetate or recrystallization to afford the pure dithiocarbamate. 

Figure 10. Eyring plots for the quenching of Oj Ag) in carbon disulfide by trans-2-butene (A), 2-methylpropene ( ), cis-2-butene (O), 2-methyl-2-butene (V), and 2,3-dimethyl-2-butene ( ). From [151] with permission. Copyright 1982, American Chemical Society.

The treatment of a ketone enolate with carbon disulfide followed by quenching with methyl iodide affords a-di(methylthio)methylene ketones (37). Methylation occurs at both S atoms as contrasted to the alkylation of 2-carbo-methoxycyclohexanone enolate which takes place at C. 

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