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Alcohol oxidation is a collection of oxidation reactions in organic chemistry that convert alcohols to aldehydes, ketones, carboxylic acids, and esters. The reaction mainly applies to primary and secondary alcohols. Secondary alcohols form ketones, while primary alcohols form aldehydes or carboxylic acids. [1] A variety of oxidants can be used.
In practice, the reverse reaction occurs: molecular chromic acid dehydrates. Some insights can be gleaned from observations on the reaction of dichromate solutions with sulfuric acid. The first colour change from orange to red signals the conversion of dichromate to chromic acid.
For oxidations to the aldehydes and ketones, two equivalents of chromic acid oxidize three equivalents of the alcohol: 2 HCrO 4 − + 3 RR'C(OH)H + 8 H + + 4 H 2 O → 2 [Cr(H 2 O) 6] 3+ + 3 RR'CO. For oxidation of primary alcohols to carboxylic acids, 4 equivalents of chromic acid oxidize 3 equivalents of the alcohol. The aldehyde is an ...
Further condensation reactions can occur in strongly acidic solution with the formation of trichromates, Cr 3 O 2− 10, and tetrachromates, Cr 4 O 2− 13. [2] All polyoxyanions of chromium(VI) have structures made up of tetrahedral CrO 4 units sharing corners. [3] The hydrogen chromate ion, HCrO 4 −, is a weak acid: HCrO − 4 ⇌ CrO 2−
Babler oxidation mechanism. The reaction proceeds through the formation of a chromate ester (1) from nucleophilic attack of the chlorochromate by the allylic alcohol.The ester then undergoes a [3,3]-sigmatropic shift to create the isomeric chromate ester (2).
The Collins oxidation is an organic reaction for the oxidation of primary alcohols to aldehydes. It is distinguished from other chromium oxide-based oxidations by the use of Collins reagent, a complex of chromium(VI) oxide with pyridine in dichloromethane. [1] [2] Mechanism of the Collins oxidation [3]
A 1,2-Wittig rearrangement is a categorization of chemical reactions in organic chemistry, and consists of a 1,2-rearrangement of an ether with an alkyllithium compound. [1] The reaction is named for Nobel Prize winning chemist Georg Wittig. [2] [3] The intermediate is an alkoxy lithium salt, and the final product an alcohol.
The reaction usually requires a catalyst, such as concentrated sulfuric acid: R−OH + R'−CO 2 H → R'−CO 2 R + H 2 O. Other types of ester are prepared in a similar manner−for example, tosyl (tosylate) esters are made by reaction of the alcohol with 4-toluenesulfonyl chloride in pyridine.