Selenium chloride, formation

Samarium (III) nitrate, analysis of anhydrous, 6 41 Selenic acid, crystalline, 3 137 Selenides, precipitation of pure metallic, from solutions of hydrogen selenide, 2 185 Selenium, red and gray, 1 119 Selenium (II) chloride, formation of, by selenium(IV) chloride, 6 127... 

The direct combination of selenium and acetylene provides the most convenient source of selenophene (76JHC1319). Lesser amounts of many other compounds are formed concurrently and include 2- and 3-alkylselenophenes, benzo[6]selenophene and isomeric selenoloselenophenes (76CS(10)159). The commercial availability of thiophene makes comparable reactions of little interest for the obtention of the parent heterocycle in the laboratory. However, the reaction of substituted acetylenes with morpholinyl disulfide is of some synthetic value. The process, which appears to entail the initial formation of thionitroxyl radicals, converts phenylacetylene into a 3 1 mixture of 2,4- and 2,5-diphenylthiophene, methyl propiolate into dimethyl thiophene-2,5-dicarboxylate, and ethyl phenylpropiolate into diethyl 3,4-diphenylthiophene-2,5-dicarboxylate (Scheme 83a) (77TL3413). Dimethyl thiophene-2,4-dicarboxylate is obtained from methyl propiolate by treatment with dimethyl sulfoxide and thionyl chloride (Scheme 83b) (66CB1558). The rhodium carbonyl catalyzed carbonylation of alkynes in alcohols provides 5-alkoxy-2(5//)-furanones (Scheme 83c) (81CL993). The inclusion of ethylene provides 5-ethyl-2(5//)-furanones instead (82NKK242). The nickel acetate catalyzed addition of r-butyl isocyanide to alkynes provides access to 2-aminopyrroles (Scheme 83d) (70S593). 

Various electrophilic selenium reagents such as those described in Scheme 4.3 can be used. V-Phenylselenylphthalimide is an excellent reagent for this process and permits the formation of large ring lactones." The advantage of the reagent in this particular application is the low nucleophilicity of phthalimide, which does not compete with the remote internal nucleophile. The reaction of phenylselenenyl chloride or V-phenylselenenylphthalimide with unsaturated alcohols leads to formation of (3-phenylselenenyl ethers. 

Phenylnaphthalene has been prepared by the reaction of a-halonaphthalenes with mercury diphenyl3 6 or with benzene in the presence of aluminum chloride,6 and by means of the Gri-gnard synthesis, starting with either bromobenzene, cyclohexyl chloride, and a-tetralone 7 or with a-bromonaphthalene and cyclohexanone.6 8 9 Dehydrogenation of the reduced naphthalene has been accomplished by the use of sulfur,6 bromine,8 platinum black, or selenium.7 The formation of the hydrocar-... 

The chlorides of certain non-metals such as phosphorus have a similar action on selenium, possibly on account of previous dissociation with formation of chlorine.4... 

The monochloride is soluble in various inert organic liquids, more particularly in benzene, chloroform, carbon tetrachloride and carbon disulphide, without undergoing chemical change. It is an exothermic compound, its heat of formation from gaseous chlorine and the amorphous modification of selenium being 22-1 Cals.1 Water causes a gradual decomposition of the chloride, selenium dioxide and selenium being formed 2... 

Selenium monochloride behaves as a strong chlorinating agent towards metals, metallic selenides and hydrocarbons.3 Phosphorus displaces selenium from the chloride with formation of phosphorus trichloride.4 Chlorine converts it into the tetrachloride. 

Selenium oxychloride absorbs all light up to a wave-length of 4050pp. It is miscible with chloroform, carbon disulphide and benzene without chemical change. It is also soluble in carbon tetrachloride, but after a time reaction takes place with formation of selenium tetrachloride and carbonyl chloride.10 At the ordinary temperatures selenium oxychloride is not miscible with the paraffin hydrocarbons,... 

Dry hydrogen sulphide interacts with selenium oxychloride with the formation of yellow selenium sulphide and evolution of hydrogen chloride. There is a development of heat which dissociates the selenium sulphide into sulphur and red selenium. Sulphur dioxide has no action on the hot anhydrous oxychloride, but if water is present there is a deposition of selenium. Sulphur trioxide is soluble in selenium oxychloride, forming a thick solution which is a very powerful solvent for the oxides of the rare earth metals. When the oxychloride is brought into contact with finely divided barium sulphate, the latter is at once peptised and becomes gelatinous in appearance,1 but when subsequently treated with water the sulphate immediately changes back to the ordinary form. 

A repetition of the foregoing work by Meyer and Pawletta,4 however, failed to confirm the production of selenium trioxide. According to these investigators, the dissolution of selenium in selenium oxychloride results in the formation of selenious chloride, and the precipitate obtained by the action of ozone is a mixture of this salt with selenium dioxide. Furthermore, substitution of carbon tetrachloride or glacial acetic acid for selenium oxychloride did not lead to the separation of the tri oxide. 

The reaction of bis-phenylpropargyl ether (321) with tris(triphenylphosphine)rhodium chloride in benzene or toluene led to the formation of the unusual organometallic compound (322), which can be viewed as a derivative of an oxygen-rhodium pentalene system. Reaction of the rhodium complex (322) with sulfur leads to the corresponding 4,6-diphenyl-l,3-dihydro[3,4-c]furan (323). The selenium and tellurium analogs (324) and (325) were made in a similar manner (Scheme 111) (76LA1448). 

When magnesium bromohydroselenide reacts with ethyl chloro-formate or acetyl chloride it gives, respectively, ethoxyseleno-formic acid, C2H5O.COSeH, and selenoacetic acid, CH3.COSeH, products in which one atom of oxygen in the carboxyl group is replaced by selenium. 

Triphenyl selenium bromide, (C6H5)3SeBr, is formed when the foregoing chloride is dissolved in boiling ethylene dibromide. It is crystallised from methyl ethyl ketone and melts with decomposition at 236° C., heating at this temperature causing decomposition with formation of diphenyl selenide and bromobenzene. 

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