Alkanes permanganate

Trifluoroacetic acid is a useful medium for a number of oxidation reactions It IS highly resistant to strong oxidants, even to permanganates and chromates For instance, various alkanes, cycloalkanes, and arenes can be oxidized degradatively by potassium permanganate in trifluoroacetic acid under mild conditions [28]... 

Finally, it may be noted that the manganese and chromium oxyanions (permanganate and chromate) are known to oxidize alkanes readily (102). In these reactions there is not any direct interaction between the transition metal and the alkane the favored mechanism for chromate oxidation is... 

Metallic oxidants, namely, chromic acid and potassium permanganate, may be used to oxidize alkanes to alcohols or ketones, but these reagents have only limited synthetic value. Alkaline KMnC>4 is rather ineffective, mainly because of the insolubility of alkanes in the aqueous solution of the reagent. Oxidations in acidic solutions such as aqueous CF3COOH,108 or the use of special reagents such as benzyltriethylammonium permanganate109 may give better results. 

Arenes can also be cleaved with peroxyacetic acid831 and permanganate.636,832 Ru04 effectively oxidizes arenes to cleavage products with the use of a cooxidant such as NaT04. Violent reaction with benzene and immediate oxidation of several other aromatics such as triphenylmethane and tetralin834 take place, but oxidation products could not be isolated. Since alkanes are resistant to Ru04,... 

The alkenes are distinguished from the alkanes by their solubility in concentrated sulphuric acid and their characteristic reactions with dilute potassium permanganate solution and with bromine. Characterisation may be based upon the determination of their physical and/or spectral properties. Characterisation by way of solid adducts with nitrosyl chloride has been quite widely used in the terpene field the preparation of adducts with 2,4-dinitrobenzenesulphenyl chloride is described below (see also Section 8.1.1, p. 1128). 

Aldehydes Alkanes Benedict s test Dichromate test 2,4-Dinitrophenylhydrazine (2,4-DNP) Fehling test Iodoform test Oxime Permanganate test Semicarbazone Tollen s test No test Positive for all aldehydes Positive for all aldehydes Positive for all aldehydes (and ketones) Positive for all aldehydes Positive only for acetaldehyde Positive for all aldehydes (and ketones) Positive for all aldehydes Positive for all aldehydes (and ketones) Positive for all aldehydes... 

Reaction with potassium permanganate. Dilute or alkaline solutions of KMn04 oxidize unsaturated compounds. Alkanes and aromatic compounds are generally unreactive. Evidence that a reaction has occurred is observed by the loss of the purple color of KMn04 and the formation of the brown precipitate manganese dioxide, Mn02. 

Aqueous potassium permanganate was added to the two test tubes on the left. One test tube contains an alkane compound. The other test tube contains an alkene compound. Which is which ... 

A10% solution of potassium permanganate is bright purple. When this reagent reacts with an olefin, the purple color disappears and a fine brown suspension of manganese dioxide may be seen. While we will use permanganate simply to distinguish between alkenes and alkanes, it is also an important preparative reagent ... 

Simple alkyl halides respond to the common characterization tests in the same manner as alkanes they are insoluble in cold concentrated sulfuric acid they are inert to bromine in carbon tetrachloride, to aqueous permanganate, and to chromic anhydride. They arc readily distinguished from alkanes, however, by qualitative analysis (Sec. 2.25), which shows the presence of halogen. 

---