Sulfides from halides

Vinyllithium [917-57-7] can be formed direcdy from vinyl chloride by means of a lithium [7439-93-2] dispersion containing 2 wt % sodium [7440-23-5] at 0—10°C. This compound is a reactive intermediate for the formation of vinyl alcohols from aldehydes, vinyl ketones from organic acids, vinyl sulfides from disulfides, and monosubstituted alkenes from organic halides. It can also be converted to vinylcopper [37616-22-1] or divinylcopper lithium [22903-99-7], which can then be used to introduce a vinyl group stereoselectively into a variety of a, P-unsaturated systems (26), or simply add a vinyl group to other a, P-unsaturated compounds to give y, 5-unsaturated compounds. Vinyllithium reagents can also be converted to secondary alcohols with trialkylb o r ane s. 

Since cbiral sulfur ylides racemize rapidly, they are generally prepared in situ from chiral sulfides and halides. The first example of asymmetric epoxidation was reported in 1989, using camphor-derived chiral sulfonium ylides with moderate yields and ee (< 41%) Since then, much effort has been made in tbe asymmetric epoxidation using sucb a strategy without a significant breakthrough. In one example, the reaction between benzaldehyde and benzyl bromide in the presence of one equivalent of camphor-derived sulfide 47 furnished epoxide 48 in high diastereoselectivity (trans cis = 96 4) with moderate enantioselectivity in the case of the trans isomer (56% ee). ... 

In 1978 and 1980 the coupling of aryl bromides and iodides with both aliphatic and aromatic thiols was first reported in the presence of NaO-t-Bu and Pd(PPh3)4 (Equation (35)).118,119 In contrast to aryl halide aminations and etherifications, the thiation reactions did not require unusual catalysts. Yet, reactions that form aryl alkyl sulfides from alkyl thiols occurred in modest yields in many cases ... 

Several palladium catalysts for formation of aryl sulfides from aryl halides have been investigated more recently. A combination of Pd2(dba)3 and DPEphos catalyzed the formation of a broad range of diaryl sulfides in the presence of 1 mol.% palladium and NaO-t-Bu base in toluene solvent.12,rThe highest yields of alkyl aryl sulfides were obtained from aryl triflates and n-butyl thiol catalyzed by a combination of palladium acetate and BINAP. However, these reactions contained 10 mol.% catalyst, were long, and required deactivated aryl triflates. A combination of Pd2(dba)3 and DPPF catalyzed the coupling of thiols with resin-bound aryl halides.121... 

The palladium-catalyzed formation of sulfides can generate polyphenylene sulfide from a dithiol and a dibromoarene, or from 4-bromobenzenethiol (Equation (38)).17 In 1984 Asahi Glass obtained patents for the formation of this polymer in the presence of palladium and nickel catalysts.125,126 In addition, Gingras reported palladium-catalyzed couplings of aryl halides and thiols to form discrete phenylene sulfide oligomers.127,128 A number of polyphenylene sulfide wires, ranging from dimeric to pentameric structures, were prepared by the palladium coupling, albeit in modest yields ... 

Innocenti et al. have studied the kinetics [101] of two-dimensional phase transitions of sulfide and halide ions, as well as electrosorption valency [102] of these ions adsorbed on Ag(lll). The electrode potential was stepped up from the value negative enough to exclude anionic adsorption to the potential range providing stability of either the first or the second, more compressed, ordered overlayer of the anions. The kinetic behavior was interpreted in terms of a model that accounts for diffusion-controlled random adsorption of the anions, followed by the progressive polynucleation and growth. 

Potentiometric Titrations. If one wishes to analyze electroactive analytes that are not ions or for which ion-selective electrodes are not available, two problems arise. First, the working electrodes, such as silver, platinum, mercury, etc, are not selective. Second, metallic electrodes may exhibit mixed potentials, which may arise from a variety of causes. For example, silver may exchange electrons with redox couples in solution, sense Ag+ via electron exchange with the external circuit, or tarnish to produce pH-sensitive oxide sites or Ag2S sites that are sensitive to sulfide and halide. On the other... 

It should not be supposed that crystal defects enter into the picture only as nuisances which the chemist seeks to avoid or eliminate. Actually, certain optical and electrical properties of oxides, sulfides, and halides have been found to depend strongly on the nature and extent of crystal defects. Indeed, semiconductivity, fluorescence (absorption of radiation and emission of less energetic radiation), and phosphorescence (delayed fluorescence) of some salts may be spectacularly increased, not only by a small stoichiometric excess of one of the constituents, but also by addition of very tiny quantities of a foreign ion. Perhaps the best known example is the case of zinc sulfide which, when precipitated from aqueous solution and dried at low temperatures, shows negligible fluorescence upon exposure to ultraviolet light. When the sulfide is heated to... 

This coupling is equally applicable to alkyl-, aryl-, and vinyllithium reagents. The products are obtained in generally good yield and in 98-100% isomeric purity. The reaction can also be used to prepare vinyl sulfides from vinyl halides and a lithium thiolate (equation II). 

Symmetrical sulfides are obtained in 70-90% yields by refluxing aqueous alcoholic solutions of halides with sodium sulfide. The nonahydrate of sodiiun sulfide is a satisfactory reagent for the reac-tion. Tetramethylene and pentamethylene halides give cyclic sulfides, e.g., tetramethylene sulfide (tetrahydrothiophene) (64%). Halides containing several other important functional groups have been employed. Typical examples include methallyl chloride, and halides with hydroxyl, ethoxyl, carboxyl, and diethylamino groups in the beta position. A dry synthesis of phenyl sulfide from calcium oxide, sulfur, and chlorobenzene at 300° has been reported. ... 

A variety of other functional groups may be present in either the halide or the mercaptan. Olefinic sulfides are obtained by the action of allyl halides on benzyl or phenyl mercaptides. Ethylene, tri-methylene, and 1-pentene chlorohydrins give hydroxyalkyl sulfides, from which chloroalkyl sulfides are obtained by the Darzens procedure (method 33) i -i pbenacyl chloride gives keto sulfides of the type CjHsCOCHjSR. Alkylmercapto acids are prepared from either halo acids... 

WiUiams 1., Wang N.-Y., Cicerone R. 1., Yagi K., Kurihara M., and Terada E. (1999) Atmospheric methyl halides and dimethyl sulfide from cattle. Global Biogeochem. Cycles 13, 485-491. 

A still unresolved problem is the structure of the often used adducts from phosphorus trihalides and carboxylic acid amides, which might be described by the formulae (8) or (9). With the aid of in situ generated adducts of acid amides and PX3 amidines, isonitriles, quinazolinones, alkyl chlorides, aminomethylenediphosphonic acids, carbamoyl halides, triformylaminomethane, 1,3,4-oxadia-zoles, sulfides (from sulfoxides), nitriles (from primary nitro compounds)" and bromoqui-nolines (from methoxyquinolines)" have been prepared. 

Murahashi, S., Yamamura, M., Yanagisawa, K., Mita, N., Kondo, K. Stereoselective synthesis of alkenes and alkenyl sulfides from alkenyl halides using palladium and ruthenium catalysts. J. Org. Chem. 1979,44, 2408-2417. 

Sulfides, or thioethers, are sulfur analogues of ethers, and like ethers they can be either symmetrical (R2S) or unsymmetrical (RSR1, where R and R are different). Sulfides can be prepared from alkyl halides by a Williamson-type synthesis with sodium hydrogen sulfide, sodium thiolate or sodium sulfide from alkyl or aryl halides via the Grignard reagent (11) from alkenes by radical-catalysed addition of thiols or by reduction of sulfoxides (Scheme 9).2b... 

The catalysts described above were prepared via low temperature precipitation from non-aqueous solution (J). This technique involves the precipitation of the transition metal sulfide from a non-aqueous solvent such as ethyl acetate by dissolving the appropriate transition metal halide in the solvent and reacting it metathetically with a sulfiding agent such as lithium sulfide to precipitate the insoluble sulfide for example ... 

The popular redox reactions for the formation of metal oxides, sulfides or halides from the elements even require a nuclear atomic model for the changes from atoms to ions. They are not at all suitable for introduction or use of the particle concept because the limits of the particle model would be way exceeded [4]. 

Sodium sulfide and sodium sulfide -f- sulfur Sym. thioethers and disulfides from halides... 

More recently, Reddy and Varma (1997a) showed that Ce,Na-Y zeolite (72% of Ce exchanged) is an effective catalyst in the synthesis of organic sulfides from cyclohexanethiols and thiophenol with alkyl halides. Yields to alkylated products from 72 to 92%, depending on the reactants, have been reported. 

A) and used in organic synthesis. a-Lithio sulfides give useful carbanion reactions and sulfur ylids can be formed (secs. 8.6, 8.8.B). The difficulties in preparing primary and secondary amines by traditional methods (from halides or tosylates via reaction with imides or azides, sec. 2.7) make the hydroboration-amination sequence a mild and useful alternative for the synthesis of amines. 

Cobaltous chloride I sodium sulfide j calcium hydroxide jmethyl iodide a-Ketocarboxylic acids from halides Hal COCOOH... 

They however are considered as the most difficult contaminants to remove from biogas [14, 15, 38, 41 3], And the presence of siloxanes makes also more complex the issue of purification of biogases from sulfide and halide compounds [17] due to competitive adsorption of different biogas contaminants [42], For instance, the adsorption of the different compounds follows the ranking water > aromatics > siloxanes > halocarbons, halocarbons. Finally, other gas trace compounds (i.e., linear, aromatic, and halogenated hydrocarbons), typically found in waste-derived fuels, are also known to cause detrimental effects in the fuel cell catalysts [3, 44,45]. 

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