Oxidation of alcohols and aldehydes to carboxylic acids

Almost all the oxidants and processes described in the preceding Sections can be applied also to conversion of alcohols and aldehydes into carboxylic acids. When acidic reagents are used with alcohols, esters are formed as by- 

Criegee, Handbuch der Katalyse, Springer-Verlag, Vienna, 1943, Vol. 7, Part 1, p. 590. 

10-Fluoro-l-decanol is converted by chromium(vi) oxide in glacial acetic acid into the corresponding fluoro carboxylic acid in 93% yield.478 

2-Furoic acid has been prepared as follows, in a modification of an older process 479 

2-Furaldehyde (19 g) is dissolved in pyridine (50 ml) and cooled in ice-salt. A solution of potassium permanganate (21 g) in pyridine (280 ml) and water (120 ml) is then added with rapid stirring, at such a rate that the temperature does not rise above — 3°. The mixture is stirred for 30 min after the addition, then filtered from the manganese dioxide formed, and the latter is washed with a little pyridine. The solvent is distilled off from the filtrate in a vacuum, and the dry residue is acidified with dilute hydrochloric acid and extracted with ether. Evaporation of the ether affords 2-furoic acid (19 g, 86%) as yellowish crystals. 

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