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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 ...
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).
It is typically prepared by treating of red lead with acetic acid and acetic anhydride (Ac 2 O), which absorbs water. The net reaction is shown: [4] [5] Pb 3 O 4 + 4 Ac 2 O → Pb(OAc) 4 + 2 Pb(OAc) 2. The remaining lead(II) acetate can be partially oxidized to the tetraacetate by Cl 2, with a PbCl 2 by-product:
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).
Through a variety of mechanisms, the removal of a hydride equivalent converts a primary or secondary alcohol to an aldehyde or ketone, respectively. The oxidation of primary alcohols to carboxylic acids normally proceeds via the corresponding aldehyde, which is transformed via an aldehyde hydrate (gem-diol, R-CH(OH) 2) by reaction with water ...