Selenium dioxide

Selenium dioxide (SeO₂) is an inorganic compound used as an oxidizing agent and as a reagent in organic synthesis. It is a polymeric solid that forms selenium-containing species in solution.

Riley oxidation: An oxidation of an allylic or benzylic methylene group to a carbonyl group using selenium dioxide. This named reaction illustrates SeO₂'s characteristic oxidation of allylic positions.
Allylic alcohol: An alcohol whose hydroxyl-bearing carbon is adjacent to a carbon–carbon double bond. Allylic alcohols are common products of SeO₂ oxidation of alkenes.
Selenium–oxygen bond: A chemical bond between selenium and oxygen, found in inorganic and organoselenium compounds. These bonds define SeO₂'s structure and its transformations in solution.
Chromium trioxide: An inorganic chromium(VI) oxide used as a strong oxidant in laboratory and industrial chemistry. It offers broader alcohol oxidation chemistry, whereas SeO₂ is often selected for allylic oxidation.
Selenium poisoning: Illness caused by excessive exposure to selenium compounds. SeO₂ is toxic, so exposure control is essential during preparation and use.
Allylic oxidation: Oxidation of a carbon–hydrogen bond at a carbon adjacent to a carbon–carbon double bond. SeO₂ is a classic reagent for converting allylic positions into alcohols or carbonyl compounds.
α,β-Unsaturated carbonyl compound: A carbonyl compound with a carbon–carbon double bond between its alpha and beta carbons. SeO₂ can convert carbonyl compounds into these conjugated products by oxidative dehydrogenation.
Oxidation state: A formal charge assigned to an atom by treating its bonds as ionic. Selenium is in the +4 oxidation state in SeO₂ and can be reduced during oxidations.
Pyridinium chlorochromate: An organic salt of chromium(VI) used to oxidize alcohols under relatively anhydrous conditions. It oxidizes alcohol functional groups rather than reproducing SeO₂'s characteristic allylic functionalization.
Hazardous waste: Waste that poses substantial risks to human health or the environment and requires controlled handling. Selenium-containing reaction residues require dedicated collection and disposal rather than ordinary drain disposal.

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Selenic acidRelated: Oxidation of selenium dioxide provides a route to selenic acid and selenates.