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Selenium oxide may refer to either of the following compounds: Selenium dioxide, SeO 2; Selenium trioxide, SeO 3; Diselenium pentoxide, Se 2 O 5 This page was last ...
Oxidations involving selenium dioxide are often carried out with catalytic amounts of the selenium compound and in presence of a sacrificial catalyst or co-oxidant such as hydrogen peroxide. SeO 2 -based oxidations sometimes afford carbonyl compounds such as ketones , [ 24 ] β- Pinene [ 25 ] and cyclohexanone oxidation to 1,2-cyclohexanedione ...
Solid SeO 2 is a one-dimensional polymer, the chain consisting of alternating selenium and oxygen atoms. Each Se atom is pyramidal and bears a terminal oxide group. The bridging Se-O bond lengths are 179 pm and the terminal Se-O distance is 162 pm. [5] The relative stereochemistry at Se alternates along the polymer chain (syndiotactic).
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.
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.
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.
Pentafluoroselenium hypofluorite can also formed from selenium oxyfluoride and fluorine gas in the presence of potassium fluoride. [4] [5] SeOF 2 + KF → K + [SeOF 3] − — F 2 → K + [SeOF 5] − — F 2 → KF + SeOF 6. The reaction of fluorine gas and Hg(OSeF 5) 2 produces SeOF 6 in much higher yield and with less SeF 6. [3]
Selenium in these reactions is almost always stereogenic, and the effect of epimerization at selenium (which is acid-catalyzed and occurs readily) on the elimination reaction is nearly unknown. In one example, separation and warming of selenoxides 1 and 2 revealed that 2 decomposes at 0 °C, while 1 , which presumably has more difficulty ...