Sulfur and Selenium Compounds

Some Physical Properties of Selenium and Sulfur Compounds (11)... 

Thiols and sulfides are occasionally prepared by treatment of Grignard reagents with sulfur.Analogous reactions are known for selenium and tellurium compounds. 

Stability Unstable in air. Protect from water or moisture. Store away horn heat or ignition sources and sulfur compounds. Reacts with sulfur and sulfur compounds, producing highly toxic VX or VX-like compounds. It completely dissolves polymethylmethacrylate. It is incompatible with calcium hypochlorite (HTH), many chlorinated hydrocarbons, selenium, selenium compounds, moisture, oxidants, and carbon tetrachloride. 

Selenium (and sulfur) dichlorides are useful reagents for the synthesis of organoselenium compounds,18 nitrogen selenium heterocycles19-21 and other selenium compounds. The key steps in these reactions usually involve a... 

The FCLD has been particularly useful as a highly sensitive means of measuring volatile sulfur, selenium, and tellurium compounds in studies of bacterial methylation [67, 111-114], Because of its high sensitivity to phosphinate esters [68], the FCLD could potentially serve as a monitor for nerve gases. 

This section includes oxidations of alkanes and cycloalkanes, alkenes and cycloalkenes, dienes, alkynes, aromatic fluorocarbons, alcohols, phenols, ethers, aldehydes, ketones and carbohydrates, carboxylic acids, nitrogen compounds, and organoelement compounds, such as boron, phosphorus, sulfur, selenium, and iodine compounds, and steroids. 

Selenium forms thio"-type compounds, such as SeS03 by reaction of selenium and sulfur tnoxide, SeS032 (selenosulfates) by reaction of selenium and sulfites, SeSy (selenosulfides) by reaction of selenium with sulfides, as well as diselenides, Se2i, and polyselenides, Set2-. 

Recent progress on the use of hypervalent iodine reagents for the construction of heteroatom-heteroatom bonds is reviewed. Reactions of aryl-A3-iodanes with heteroatom substrates derived from third-row elements and beyond are considered first, and an unusual example of heteroatom-heteroatom bond formation with diaryliodonium salts is then discussed. Finally, the use of sulfonylimino(aryl)iodanes for imidations of phosphorus, sulfur, selenium, and arsenic compounds, including enantioselective transformations (S,Se), and alternate hypervalent iodine approaches to N-sulfonylsulfilimines and N-sulfonylarsinimines are summarized. 

As presented for the type 1 reactions in Scheme 6, selenium- and sulfur diimido compounds, 68-71, can undergo a two-step reaction sequence when treated with an allyl alkene to form the allyl amine. 

Professor A. Haas (Bochum, Germany) deals with some of the recent developments in chalcogen-heterocycles with particular emphasis on simple sulfur, selenium, and tellurium compounds that can serve as synthons for the preparations of various heterocycles. 

Analogous sulfur, selenium, and tellurium compounds are easily prepared by reaction of the aluminum halides with the appropriate aluminum chalcogenide (equation 35). 

The chemistry of the selenium and tellurium compounds is broadly similar to that of the sulfur compounds. 

Selenium is widely dispersed. It is found, for example, in igneous rocks, volcanic sulfur deposits, hydrothermal deposits, and copper ores. Selenium is used in the electronics industry for the manufacture of rectifiers and photoconductivity cells. Selenium and its compounds are also used as additives in chromium-plating, glass, ceramics, pigment, rubber, photography, lubricants, pharmaceuticals, and organic substances. 

Selenium and tellurium are more electropositive elements than sulfur and, in general, the chemistry of organic selenium and tellurium compounds is more complicated and difficult than that of the sulfur analogues, not forgeting the toxicity of selenium and the noxiousness of low molecular organic selenium and tellurium compounds. 

The twofold extrusion of nitrogen and sulfur and selenium and sulfur from 1-thia- and l-selena-3,4-diazolines(77), readily available from the reaction of diazoalkanes with thio- and selenaketones, respectively, as well as from the reductive coupling of carbonyl compounds such as 78, is the preferred method for preparation of olefins of type I and II (98,99). Examples of the extrusion method, developed by Barton (100), and the McMurry reaction (101) are given in Scheme 1. 

Selenium and tellurium and their compounds produce very unpleasant and dangerous physiological reactions. They are hazardous both through inhalation as dusts and through skin absorption from solution. Because of these properties and because of the toxicity of the sulfur dioxide used as a solvent, the reactions should be conducted in an efficient fume hood. Rubber gloves and apron are recommended to prevent contact with solutions containing selenium and tellurium compounds as well as the dangerous pentafluorides of antimony and arsenic. 

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