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The carbon–carbon bond in a vicinal diol (glycol) is cleaved and instead the two oxygen atoms become double-bonded to their respective carbon atoms. Depending on the substitution pattern in the diol, these carbonyls will be ketones and/or aldehydes. [1] Glycol cleavage is an important for determining the structures of sugars.
In organic chemistry, the Malaprade reaction or Malaprade oxidation is a glycol cleavage reaction in which a vicinal diol is oxidized by periodic acid or a periodate salt to give the corresponding carbonyl functional groups. [1] [2] The reaction was first reported by Léon Malaprade in 1928. [3] [4] Amino alcohols are also cleaved. [5]
Periodic acid (/ ˌ p ɜːr aɪ ˈ ɒ d ɪ k / per-eye-OD-ik) is the highest oxoacid of iodine, in which the iodine exists in oxidation state +7. It can exist in two forms: orthoperiodic acid, with the chemical formula H 5 IO 6, and metaperiodic acid, which has the formula HIO 4. Periodic acid was discovered by Heinrich Gustav Magnus and C. F ...
Sodium periodate is an inorganic salt, composed of a sodium cation and the periodate anion.It may also be regarded as the sodium salt of periodic acid.Like many periodates, it can exist in two different forms: sodium metaperiodate (formula NaIO 4) and sodium orthoperiodate (normally Na 2 H 3 IO 6, but sometimes the fully reacted salt Na 5 IO 6).
Two mechanisms are proposed for the Criegee oxidation, depending on the configuration of the diol. [6] [7] If the oxygen atoms of the two hydroxy groups are conformationally close enough to form a five-membered ring with the lead atom, the reaction occurs via a cyclic intermediate.
Where solubility is an issue periodic acid may be used, as this is soluble in alcohols; phase transfer catalysts are also effective in biphasic reaction mixtures. In extreme cases the periodate may be exchanged for lead tetraacetate which reacts in a similar manner and is soluble in organic solvents (Criegee oxidation).
Two ketyl groups react in a coupling reaction yielding a vicinal diol with both hydroxyl groups deprotonated. Addition of water or another proton donor gives the diol. With magnesium as an electron donor, the initial reaction product is a 5-membered cyclic compound with the two oxygen atoms coordinated to the oxidized Mg 2+ ion.
A monosaccharide with nine carbons. An example is sialic acid. Periodic acid: Periodic acid Or per-iodic acid, is pronounced / ˌ p ɜːr aɪ ˈ ɒ d ɪ k / PURR-eye-OD-ik and not * / ˌ p ɪər i ˈ ɒ d ɪ k / PEER-ee-OD-ik. It refers to one of two interconvertible species: HIO 4 (metaperiodic acid), or H 5 IO 6 (orthoperiodic acid