Organoselenium compounds

The determination of dimethylselenides and diethylselenide in scrubbed air samples has been discussed [699]. This method is based on a gas chromatographic-atomic absorption procedure and could, no doubt, be adapted for the analysis of waters. 

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The chemical properties of organosulfur, organoselenium, and organoteUurium compounds are markedly similar. Because bond stabUity with carbon decreases with the increasing atomic number of the element, thermal stabUity decreases, whereas oxidation susceptibUity increases to such an extent that alkyl teUurides are oxidized rapidly by air at room temperature. As a result, less has been written concerning the chemistry of organoteUurium than organoselenium compounds. Nevertheless, a sizable Uterature exists (29,55—59). 

Organoselenium compounds in particular, once ingested, are slowly released over prolonged periods and result in foul-smelling breath and perspiration. The element is also highly toxic towards grazing sheep, cattle and other animals, and, at concentrations above about 5 ppm, causes severe disorders. Despite this, Se was found (in 1957) to play an essential dietary role in animals and also in humans — it is required in the formation of the enzyme glutathione peroxidase which is involved in fat metabolism. It has also been found that the Incidence of kwashiorkor (severe protein malnutrition) in children is associated with inadequate uptake of Se, and it may well be involved in protection... 

The principal classes of organoselenium compound are summarized in the scheme above which indicates the central synthetic role of... 

These facts, together with many other examples of the peculiar chemical behavior of organotellurium compounds (95UK527), emphasize their specific reactivity and explain why a number of methods developed for preparation of organosulfur and organoselenium compounds are inapplicable for their tellurium analogues. 

As peracids are used peracetic acid, peroxytrifluoroacetic acid, m-chloroperben-zoic acid and others. Hydrogen peroxide or a peracid in combination with triflu-oroacetic acid or certain organoselenium compounds have been successfully employed. 

REAGENTS FOR SYNTHESIS OF ORGANOSELENIUM COMPOUNDS DIPHENYL DISELENIDE AND BENZENESELENENYL CHLORIDE... 

The natural abundance of selenium-77 is 7.58%. The chemical shift of dimethyl selenide is set equal to 0 ppm. The total chemical shift range is around 2200 ppm, organoselenium compounds covering almost the whole range. Figure 41 shows the spectrum of H2Se03 in D20, the linewidth being only... 

Organoselenium compounds have drawn much attention in the past years as synthons in organic synthesis209,210 and the chemistry of selenoketones has been reported increasingly.211 214... 

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... 

Used industrially for preparation of metallic selenides, organoselenium compounds, and preparation of semiconductor materials. 

Organolead and organoselenium compounds were separated satisfactorily by high-performance capillary electrophoresis, using /1-cyclodextrin-modified micellar electroki-netic chromatography with on-column UVV detector set at 210 nm130. 

Total recoverable13 After filtration through 0.45-p filter, <2 pg total Se/L, sometimes <1 pg/L for organoselenium compounds 27... 

Carboxylic acid complexes, 199-203 Catalysis, see also Organoselenium compounds ... 

Organochalcogen(II) compounds, 100-102 Organochalcogen(IV) compounds, 100-102 Organoselenium compounds dehalogenation reactions, 96 electrochemical reduction, 113-117 haloperoxidase-like activity, 108-113 with odd number of ligands, 100-102 one-electron oxidation, 117-118 oxidation of thiols, 102-106 redox reactions, 79-80 thioperoxidase-like activity, 108-113 Organotellurium compounds... 

Toxicity data on organotellurium compounds are still scarce in the hterature, in contrast with those of organoselenium compounds. 

Although some authors have informed that organotellurium compounds are less toxic than their selenium co-partners, further data indicated in opposition that organotellurium compounds are more toxic than organoselenium compounds. ... 

The organoselenium compounds, their chemistry, and methods of preparation are discussed in the literature (3,4,7,11,12,14,59). Selenium-containing polymers are of interest because of their semiconducting and plastic properties. The biologically important compounds include selenoaminocarboxylic acids and derivatives, selenium-containing peptides, and selenium derivatives of pyrimidines, purines, cholines, steroids, coenzyme A, and other compounds (4,14). The biochemical and medical aspects and uses of oiganoselenium compounds have also been discussed (13,14,60—62). 

Organoselenium compounds, such as phosphine selenides, are being evaluated in solvent extraction systems for silver and gold (63). Also, potential pharmaceuticals containing selenium have been prepared (64). 

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