Hot basic potassium permanganate

Strong oxidants such a hot basic potassium permanganate oxidize a ketone with an alteration of the carbon backbone. Figure 10-34 illustrates the oxidation of a ketone with permanganate followed by acidification to produce a carboxylic acid. The oxidation cleaves the carbon-carbon on one side of the carbonyl group. 

The synthesis of carboxylic acids by the oxidation of alkenes is a two-step process. In the first step, a hot basic potassium permanganate (KMnO ) solution oxidizes an alkene, and in the second step, the oxidized alkene is acidified. The process cleaves the Ccirbon backbone at the carbon-carbon double bond to produce two smaller carboxylic acid molecules. For example, oleic acid (CH3(CH2)yCH=CI-l(CI-l2)yCOOH) yields of mixture of nonanoic acid (CH3(CH2)7C00H) and nonadioic acid (HOOC(CH2)7COOH). 

Reaction of an alkene with hot basic potassium permanganate (KMn04) results in cleavage of the double bond, and formation of highly oxidized carbons. Therefore, unsubstituted carbon atoms become CO2, mono-substituted carbon atoms become carboxylates, and di-substituted carbon atoms become ketones. This can be used as a chemical test (known as the Baeyer test) for alkenes and alkynes, in which the purple colour of the KMn04 disappears, and a brown Mn02 residue is formed. 

Unsubstituted carbon atoms are oxidized to CO2, and mono-substituted carbon atoms to carboxylic acids. Therefore, oxidation of 1-butyne with hot basic potassium permanganate followed by acidification produces propionic acid and carbon dioxide. 

Treatment with hot basic potassium permanganate oxidatively cleaves the double bond of an alkene. 

The IR spectrum of compound X shows, among others, a peak near 3320 cm several peaks in the 2800-3000-cm region, and a peak near 2100 cm On oxidation with hot, basic potassium permanganate followed by acidification, X produces a five-carbon carboxylic acid and a gas. 

Compounds W and X are isomers they have the molecular formula CgHsO. The IR spectrum of each compound shows a strong absorption band near 1715 cm. Oxidation of either compound with hot, basic potassium permanganate followed by acidification yields phthalic acid. The NMR spectrum of W shows a multiplet at S 7.3 and a singlet at 8 3.4. The NMR spectrum of X shows a multiplet at 81.5, a triplet at 8 3.1, and a triplet at 8 2.5. Propose structures for W and X. 

Hot acidic potassium dichromate (K2Cr20. ) u Chromium trioxide (Cr03) in sulfuric acid (H2SO (Jones rec ent) u Hot basic permanganate followed by acidification... 

The final reaction in this section provides a method to prepare aromatic rings bonded to a carboxylic acid group. Because we do not have a direct way to attach this group, this procedure is very useful. The reaction is usually accomplished by oxidation of a methyl group to the carboxylic acid employing hot potassium permanganate in basic solution ... 

Diols are oxidatively cleaved to ketones and/or aldehydes by periodic acid (HIO4). Ozonolysis oxidatively cleaves alkenes to ketones and/or aldehydes when worked up under reducing conditions and to ketones and/or carboxylic acids when worked up under oxidizing conditions. Acidic solutions and hot basic solutions of potassium permanganate also oxidatively cleave alkenes to ketones and/or carboxylic acids. 

STRATEGY AND ANSWER In (1), we must oxidize methylbenzene to benzoic acid. To do this we use hot potassium permanganate in a basic solution followed by an acidic workup (see Section 15.13C). For (2), we must convert a carboxylic acid to an acid chloride. For this transformation we use thionyl chloride or phosphorus pentachloride (see Section 15.7). For (3), we must reduce an acid chloride to an aldehyde. For this we use lithium tri-rerf-butoxyaluminum hydride (see above). 

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