Sulfide, dimethyl solvent

Leaks in pipelines can be detected by means of a test-fluid. The test-fluid, a mixture of dimethyl sulfide in solvent, is injected into a pipeline. In the case of a leak, the test-fluid escapes through the leak, and the odorant is released from the closed compartments [1465,1466]. 

This solvent is fairly pure as received. The only impurities are water and traces of dimethyl sulfide. Dimethyl sulfide can be removed by a preliminary vacuum distillation, or by bubbling an inert gas through the solution for 10 to 20 min before use. The water content can be reduced to 10 ppm by sequential treatment with two batches of 3 A molecular sieves (activation of the sieve at 500°C for 16 h in an inert atmosphere has been advocated [62], but activation for 15 h at 300°C should suffice [52]). Calcium hydride and a number of other basic reagents have been advocated as drying agents, but in fact all of these are ineffective [32]. Tetrabutylammonium hexafluorophosphate exhibits good solubility in THF. 

Borabicyclo[3.3.1]nonane (9-BBN) has been prepared by the thermal redistribution of 9-n-propyl-9-BBN, and the hydroboration of 1,5-cyclooctadlene with borane-tetrahydrofuran complex followed by thermal isomerization of the mixture of dialkylboranes at BS C. Solutions of 9-BBN have been prepared from the hydroboration of 1,5-cyclooctad ene with borane-methyl sulfide in solvents other than THF.6 The present procedure involves the cyclic hydroboration of 1,5-cyclooctadiene with borane-methyl sulfide in 1,2-dimethoxyethane.7 Distillative removal of the dimethyl sulfide in this special solvent system provides a medium that gives high purity, large needles of crystalline 9-BBN dimer in excellent yield. The material can be handled in air for brief periods without measurable decomposition. 

Dimethyl sulfoxide is a very polar, high dipole moment, strong hydrogen bond accepting solvent It is has a high viscosity nearly equal to that of IPA. Typical impurities from the manufacturing process include dimethyl sulfide (from whidi DMSO is commonly manufactured) and dimethyl sulfone. Decomposition products include dimethyl sulfide, dimethyl sulfone, methyl mercaptan, and bis(methylthio> methane [1552]. 

Borane—dimethyl sulfide complex (BMS) (2) is free of these inconveniences. The complex is a pure 1 1 adduct, ca 10 Af in BH, stable indefinitely at room temperature and soluble in ethers, dichioromethane, benzene, and other solvents (56,57). Its disadvantage is the unpleasant smell of dimethyl sulfide, which is volatile and water insoluble. Borane—1,4-thioxane complex (3), which is also a pure 1 1 adduct, ca 8 Af in BH, shows solubiUty characteristics similar to BMS (58). 1,4-Thioxane [15980-15-1] is slightly soluble in water and can be separated from the hydroboration products by extraction into water. 

The products are Hquids, soluble in various solvents and stable over prolonged periods. Monochloroborane is an equiUbtium mixture containing small amounts of borane and dichloroborane complexes with dimethyl sulfide (81). Monobromoborane—dimethyl sulfide complex shows high purity (82,83). Solutions of monochloroborane in tetrahydrofuran and diethyl ether can also be prepared. Strong complexation renders hydroboration with monochloroborane in tetrahydrofuran sluggish and inconvenient. Monochloroborane solutions in less complexing diethyl ether, an equiUbtium with small amounts of borane and dichloroborane, show excellent reactivity (88,89). Monochloroborane—diethyl etherate [36594-41-9] (10) may be represented as H2BCI O... 

Through reaction with sulfide or elemental sulfur at 215°C, lignosulfonates can also be used in the commercial production of dimethyl sulfide and methyl mercaptan (77). Dimethyl sulfide produced in the reaction is further oxidized to dimethyl sulfoxide (DMSO), a useful industrial solvent (see Sulfoxides). 

Another product from kraft black Hquor is dimethyl sulfide. This chemical, which is added to natural gas to give it odor, is also oxidized to produce the versatile solvent, dimethyl sulfoxide (see Sulfoxides). 

The solvent can be tailored to provide selective acid gas removal based on the Hquid—gas solubiHties. For example, the Selexol process, Hcensed by Union Carbide Corporation, uses the dimethyl ether of polyethylene glycol (DMPEG) to provide high hydrogen sulfide selectivity. The solubiHty of hydrogen sulfide in DMPEG is 8—10 times that of carbon dioxide. 

With hydrogen sulfide at 500—600°C, monochlorotoluenes form the corresponding thiophenol derivatives (30). In the presence of palladium catalysts and carbon monoxide, monochlorotoluenes undergo carbonylation at 150—300°C and 0.1—20 MPa (1—200 atm) to give carboxyHc acids (31). Oxidative coupling of -chlorotoluene to form 4,4 -dimethylbiphenyl can be achieved in the presence of an organonickel catalyst, generated in situ, and zinc in dipolar aprotic solvents such as dimethyl acetamide (32,33). An example is shown in equation 4. 

Important processes commercially used are the Selexol, the Sulfinol, and the Rectisol processes. In these processes, no chemical reaction occurs between the acid gas and the solvent. The solvent, or absorbent, is a liquid that selectively absorbs the acid gases and leaves out the hydrocarbons. In the Selexol process for example, the solvent is dimethyl ether of polyethylene glycol. Raw natural gas passes countercurrently to the descending solvent. When the solvent becomes saturated with the acid gases, the pressure is reduced, and hydrogen sulfide and carbon dioxide are desorbed. The solvent is then recycled to the absorption tower. Figure 1-1 shows the Selexol process. ... 

To a suspension of 1.10 mmol of eopper(I) bromide-dimethyl sulfide in 2 mL of THF arc added 2.20 mmol of Bul.i in hexane at — 70 C und the clear solution is stirred at — 40°C for 40 min. 1.15 mmol of freshly fused zinc(Il) chloride dissolved in THF (1 M, 1.15mL) are added at - 70°C and after 15 min 1.0 mmol of the allylic halide in 1 mL of 1HF are added. After 15 h at -702C, the reaction mixture is diluted with hexane washed with sat. aq NaHC03 and sat. aq NaCI and then dried over MgS04. Tile solvent is removed, the product ratio analyzed by GC and the product is purified by chromatography. 

The solvent dependence of the reaction rate is also consistent with this mechanistic scheme. Comparison of the rate constants for isomerizations of PCMT in chloroform and in nitrobenzene shows a small (ca. 40%) rate enhancement in the latter solvent. Simple electrostatic theory predicts that nucleophilic substitutions in which neutral reactants are converted to ionic products should be accelerated in polar solvents (23), so that a rate increase in nitrobenzene is to be expected. In fact, this effect is often very small (24). For example, Parker and co-workers (25) report that the S 2 reaction of methyl bromide and dimethyl sulfide is accelerated by only 50% on changing the solvent from 88% (w/w) methanol-water to N,N-dimethylacetamide (DMAc) at low ionic strength this is a far greater change in solvent properties than that investigated in the present work. Thus a small, positive dependence of reaction rate on solvent polarity is implicit in the sulfonium ion mechanism. 

The rapid decomposition of benzoyl peroxide by dimethyl sulfide is explosive in absence of solvent. 

The parent hexathiaadamantane (185) is obtained preparatively when a solution of formic acid and hydrochloric acid in nitrobenzene is allowed to stand for several weeks in a hydrogen sulfide atmosphere the product which separated is almost insoluble in all common solvents and purification presents a problem. Only large volumes of dimethyl sulfoxide at reflux serve for recrystallization.224 The reaction of thioacetic acid with formic acid in the presence of zinc chloride gives tetramethyl-(186), monomethyl-, dimethyl-and trimethylhexathiaadamantane derivatives (187).225 Other variations include the reaction of thioacetic acid with a /i-diketone,226 and the use of boron trifluoride227 or aluminum chloride as a catalyst.228... 

The beneficial effect of added phosphine on the chemo- and stereoselectivity of the Sn2 substitution of propargyl oxiranes is demonstrated in the reaction of substrate 27 with lithium dimethylcyanocuprate in diethyl ether (Scheme 2.9). In the absence of the phosphine ligand, reduction of the substrate prevailed and attempts to shift the product ratio in favor of 29 by addition of methyl iodide (which should alkylate the presumable intermediate 24 [8k]) had almost no effect. In contrast, the desired substitution product 29 was formed with good chemo- and anti-stereoselectivity when tri-n-butylphosphine was present in the reaction mixture [25, 31]. Interestingly, this effect is strongly solvent dependent, since a complex product mixture was formed when THF was used instead of diethyl ether. With sulfur-containing copper sources such as copper bromide-dimethyl sulfide complex or copper 2-thiophenecarboxylate, however, addition of the phosphine caused the opposite effect, i.e. exclusive formation of the reduced allene 28. Hence the course and outcome of the SN2 substitution show a rather complex dependence on the reaction partners and conditions, which needs to be further elucidated. 

Matheson, Coleman and Bell anhydrous dimethyl sulfoxide was stirred over powdered calcium hydride overnight and then distilled under reduced pressure, b.p. 64-65° (4 mm.). Dimethyl sulfoxide should not be distilled at temperatures above 90° since at these higher temperatures appreciable disproportionation occurs producing dimethyl sulfone and dimethyl sulfide, the latter of which contaminates the distilled solvent. 

Much of the methyl mercaptan and dimethyl sulfide can be oxidized to dimethylsulfoxide (DMSO), a useful side product that is a common polar, aprotic solvent in the chemical industry. This is in fact the primary method... 

When ozonolysis is done in alcoholic solvents, the carbonyl oxide fragmentation product can be trapped as an a-hydroperoxy ether.146 Recombination to the ozonide is then prevented, and the carbonyl compound formed in the fragmentation step can also be isolated. If the reaction mixture is treated with dimethyl sulfide, the hydroperoxide is reduced and the second carbonyl compound is also formed in good yield.147 This procedure prevents oxidation of the aldehyde by the peroxidic compounds present at the conclusion of ozonolysis. 

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