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The general structure of an oxocarbenium ion. An oxocarbenium ion (or oxacarbenium ion) is a chemical species characterized by a central sp 2-hybridized carbon, an oxygen substituent, and an overall positive charge that is delocalized between the central carbon and oxygen atoms. [1]
Another class of oxonium ions encountered in organic chemistry is the oxocarbenium ions, obtained by protonation or alkylation of a carbonyl group e.g. R−C= + −R′ which forms a resonance structure with the fully-fledged carbocation R− + −O−R′ and is therefore especially stable:
In chemistry, an oxocarbon anion is a negative ion consisting solely of carbon and oxygen atoms, and therefore having the general formula C x O n− y for some integers x, y, and n. The most common oxocarbon anions are carbonate, CO 2− 3, and oxalate, C 2 O 2− 4. There are however a large number of stable anions in this class, including ...
Second, while oxidation occurred from the desired convex face of the silyl enol ether, the authors saw a significant number of overoxidation products that they attributed to the stability of the oxocarbenium ion intermediate under sodium bicarbonate buffered conditions.
The selectivity in the reaction is due to the stronger electron withdrawing power of the esters compared to the ethers. A stronger electron withdrawing substituent leads to a greater destabilization of the oxocarbenium ion. This slows this reaction pathway, and allows for disaccharide formation to occur with the benzylated sugar.
(Right) Denmark's model system for acetal substitution mechanism. If the S N 1 mechanism is operative for the acetal substitution, the two reactions shown here should proceed via the same oxocarbenium ion and give similar stereochemical outcomes. Results indicate that the mechanism varies depending on the Lewis acid and the R group.
Brodie also discovered in 1859 a fifth compound called graphite oxide, consisting of carbon and oxygen in ratios varying between 2:1 and 3:1; but the nature and molecular structure of this substance remained unknown until a few years ago, when it was renamed graphene oxide and became a topic of research in nanotechnology. [3]
Two proposed mechanisms include a nucleophilic displacement and an oxocarbenium ion intermediate. [11] Example of an α-glucosidase catalyzed reaction: maltotriose + water → α-glucose. Rhodnius prolixus, a blood-sucking insect, forms hemozoin (Hz) during digestion of host hemoglobin. Hemozoin synthesis is dependent on the substrate binding ...