REACTIONS AND IDENTIFICATION 395 (B) Picrates. Many picrates are unstable. (See 3 above.) (M.ps., p. 560.) (C) Oxidation of side chains. Aromatic hydrocarbons with side chains are oxidised by alkaline KMnO 4 to carboxylic acids. Proceed as for the oxidation of benzyl chloride (p. 393), using i g. of the hydrocarbon in place of the chloride. Thus toluene and ethylbenzene give benzoic acid, 0-, m-and p-xylene give phthalic acid, isophthalic acid, and tereph-thalic acid respectively (M.ps., p. 544). If desired, these crystalline acids can be further identified by making suitable crystalline derivatives according to the directions given under acids (p. 353). Aromatic hydrocarbons with unsaturated side-chains. Styrene, stilbene. Physical Properties. Styrene, C 6 H 5 CH = CH 2 , is a pleasant smelling liquid, lighter than and insoluble in water, b.p. 146°. Stilbene, C 6 H 6 CH = CHC 6 H 6 , is a colourless solid, m.p. 125°, b.p. 306°, insoluble in water. GENERAL REACTIONS.
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