Search results
Results from the WOW.Com Content Network
Selenium dioxide is prepared by oxidation of selenium by burning in air or by reaction with nitric acid or hydrogen peroxide, but perhaps the most convenient preparation is by the dehydration of selenous acid. 2 H 2 O 2 + Se → SeO 2 + 2 H 2 O 3 Se + 4 HNO 3 + H 2 O → 3 H 2 SeO 3 + 4 NO H 2 SeO 3 ⇌ SeO 2 + H 2 O
Specifically, SeO 2 will convert an allylic methylene group into the corresponding alcohol. A number of other reagents bring about this reaction. Scheme 1. Selenium dioxide oxidation. In terms of reaction mechanism, SeO 2 and the allylic substrate react via pericyclic process beginning with an ene reaction that activates the C−H bond.
The Riley oxidation is a selenium dioxide-mediated oxidation of methylene groups adjacent to carbonyls. It was first reported by Harry Lister Riley and co-workers in 1932. [ 1 ] In the decade that ensued, selenium -mediated oxidation rapidly expanded in use, and in 1939, Andre Guillemonat and co-workers disclosed the selenium dioxide-mediated ...
The conversion of valencene to nootkatone is an example of allylic oxidation. In the synthesis of some fine chemicals, selenium dioxide is used to convert alkenes to allylic alcohols: [15] R 2 C=CR'-CHR" 2 + [O] → R 2 C=CR'-C(OH)R" 2. where R, R', R" may be alkyl or aryl substituents.
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.
Allyl alcohols in general are prepared by allylic oxidation of allyl compounds, using selenium dioxide or organic peroxides. Other methods include carbon-carbon bond-forming reactions such as the Prins reaction, the Morita-Baylis-Hillman reaction, or a variant of the Ramberg-Bäcklund reaction. Hydrogenation of enones is another route.
Underwater, a catfish won’t smell the same scent we smell in the air. Anything a catfish would normally eat, such as shad, bream, and skipjack, is recommended by veteran anglers.
Selenium trioxide may be synthesized by dehydrating selenic acid, H 2 SeO 4, which is itself produced by the oxidation of selenium dioxide with hydrogen peroxide: [26] SeO 2 + H 2 O 2 → H 2 SeO 4 Hot, concentrated selenic acid reacts with gold to form gold(III) selenate.