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Organoselenium chemistry is the science exploring the properties and reactivity of organoselenium compounds, chemical compounds containing carbon-to-selenium chemical bonds. [ 1 ] [ 2 ] [ 3 ] Selenium belongs with oxygen and sulfur to the group 16 elements or chalcogens, and similarities in chemistry are to be expected.
Selenium forms two oxides: selenium dioxide (SeO 2) and selenium trioxide (SeO 3). Selenium dioxide is formed by the reaction of elemental selenium with oxygen: [5] + It is a polymeric solid that forms monomeric SeO 2 molecules in the gas phase. It dissolves in water to form selenous acid, H 2 SeO 3.
Addition rather than substitution takes place, due to the very high C–H bond dissociation energy (112 kcal/mol) that disfavors abstraction of a hydrogen atom. Addition of Cl 2 destroys the aromaticity of the benzene ring, and the addition of two more Cl 2 molecules is rapid compared to the first.
Selenium hexafluoride is the inorganic compound with the formula SeF 6. It is a very toxic colourless gas described as having a "repulsive" odor. [ 5 ] It is not widely encountered and has no commercial applications.
Selenium is found in metal sulfide ores, where it substitutes for sulfur. Commercially, selenium is produced as a byproduct in the refining of these ores. Minerals that are pure selenide or selenate compounds are rare. The chief commercial uses for selenium today are glassmaking and pigments. Selenium is a semiconductor and is used in photocells.
A second significant side reaction in reactions of ketones and aldehydes is selanylation of the intermediate selenoxide. This process leads to elimination products retaining a carbon-selenium bond, [16] and is more difficult to prevent than the seleno-Pummerer reaction. Tertiary selenoxides, which are unable to undergo enolization, do not react ...
Selenium dibromide – SeBr 2; Selenium dioxide – SeO 2; Selenium disulfide – SeS 2; Selenium hexafluoride – SeF 6; Selenium hexasulfide – Se 2 S 6; Selenium oxybromide – SeOBr 2; Selenium oxydichloride – SeOCl 2; Selenium tetrachloride – SeCl 4; Selenium tetrafluoride – SeF 4; Selenium trioxide – SeO 3; Selenoyl fluoride ...
Following rearrangement and loss of water, a second equivalent of water attacks the alpha position. Red amorphous selenium is liberated in the final step to give the 1,2-dicarbonyl product. [8] [9]: 4331 Allylic oxidation using selenium-dioxide proceeds via an ene reaction at the electrophilic selenium center.