Vanadium pentoxide, catalyst with chlorates

Fumaric acid is conveniently prepared by the oxidation of the inexpensive furfural with sodium chlorate in the presence of a vanadium pentoxide catalyst ... 

C. Fumaric acid from furfural. Place in a 1-litre three-necked flask, fitted with a reflux condenser, a mechanical stirrer and a thermometer, 112 5 g. of sodium chlorate, 250 ml. of water and 0 -5 g. of vanadium pentoxide catalyst (1), Set the stirrer in motion, heat the flask on an asbestos-centred wire gauze to 70-75°, and add 4 ml. of 50 g. (43 ml.) of technical furfural. As soon as the vigorous reaction commences (2) bvi not before, add the remainder of the furfural through a dropping funnel, inserted into the top of the condenser by means of a grooved cork, at such a rate that the vigorous reaction is maintained (25-30 minutes). Then heat the reaction mixture at 70-75° for 5-6 hours (3) and allow to stand overnight at the laboratory temperature. Filter the crystalline fumaric acid with suction, and wash it with a little cold water (4). Recrystallise the crude fumaric acid from about 300 ml. of iif-hydrochloric acid, and dry the crystals (26 g.) at 100°. The m.p. in a sealed capillary tube is 282-284°. A further recrystaUisation raises the m.p. to 286-287°. 

Other oxidizing agents have been used. Sodium chlorate with vanadium pentoxide catalyst attacks anthracene readily but is not powerful enough for the conversion of hydrocarbons of the naphthalene and phenanthrene series. An acetic acid solution of 30% hydrogen peroxide has also been used. °... 

Benzoquinone ( quinone ) is obtained as the end product of the oxidation of aniline by acid dichromate solution. Industrially, the crude product is reduced with sulphur dioxide to hydroquinone, and the latter is oxidised either with dichromate mixture or in very dilute sulphuric acid solution with sodium chlorate in the presence of a little vanadium pentoxide as catalyst. For the preparation in the laboratory, it is best to oxidise the inexpensive hydroquinone with chromic acid or with sodium chlorate in the presence of vanadium pent-oxide. Naphthalene may be converted into 1 4-naphthoquinone by oxidation with chromic acid. 

By oxidizing butyl alcohol with sodium chlorate and dilute sulfuric add, using vanadium pentoxide as a catalyst. Milas, J. Amer. Chem. Soc. 50, 493 (1928). 

With vanadium pentoxide as catalyst in an acidic medium, sodium chlorate oxidizes hydroquinone to quinone. A procedure by Underwood and Walsh calls for stirring a mixture of the reactants in 1 I. of 2% sulfuric acid until the green... 

Graebe and Liebermann378 converted anthracene into anthraquinone by oxidation with chromic acid in glacial acetic acid, although it is preferable379 to use sodium chlorate and vanadium pentoxide as catalysts. However, anthraquinone can also be prepared in good yield by use of potassium permanganate ... 

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