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STYROLENE, C 6 H 6 -CH:CH 2 , also known as phenylethylene or vinylbenzene, an aromatic hydrocarbon found to the extent of i to 4% in storax; it also occurs with crude xylene in coal tar fractions. It may be obtained from storax by distillation with water, and synthetically by heating cinnamic acid with lime, by the action of aluminium chloride on a mixture of vinyl bromide and benzene, by removing the elements of hydrobromic acid from bromethylbenzene by means of alcoholic potash, or, best, by treating /3-bromhydrocinnamic acid with soda, when it yields styrolene, carbon dioxide and hydrobromic acid. It also results on condensing acetylene, and on reducing phenylacetylene by zinc dust and acetic acid. It is a clear, strongly refractive liquid, which has a pleasant odour; it boils at 144 and has a specific gravity of 0-925 at o. Styrolene is oxidized by nitric or chromic acids to benzoic acid; reduction gives ethylbenzene; hydrochloric and hydrobromic acids yield a-haloid ethylbenzenes, e.g. C 6 H 5 -CHC1-CH 3 ; whilst chlorine and bromine give o/3-dihaloid ethylbenzenes, e.g. C 6 H 5 -CHC1-CH 2 C1.

io6o Styrolene gives origin to three series of derivatives, two of which contain the substituents in the side chain, e.g. CjHs-CChCHj or a-compounds, and CeHe-CHrCHCl, or u-compounds, whilst in the third the benzene nucleus is substituted. The a-halogen compounds are obtained by heating styrolene chloride (or bromide) with lime or alcoholic potash; they are liquids which have a penetrating odour, and yield acetophenone when heated with water to 180 . The u-chlor compound results when /3-phenyl-a-chlorlactic acid (from hypochlorous acid and cinnamic acid) is heated with water; it has a hyacinthine odour and yields phenylacetaldehyde when heated with water. Nitrostyrolene results when styrolene is treated with fuming nitric acid.

Related to styrolene is phenylacetylene, CeHs-CjCH, which results; when a-bromstyrolene or acetophenone chloride are heated to i3O o with alcoholic potash, or phenylpropiolic acid with water to 120 . It is a liquid, boiling at 139 and having a pleasant odour. It resembles acetylene in yielding metallic derivatives with ammoniacal copper and silver solutions. On solution in sulphuric acid, followed by dilution with water, it yields acetophenone.

Stilbene or toluylene, C 6 H 6 -CH : CH-CiHi, is symmetrical diphenylethylene. It may be obtained by distilling benzyl sulphide |or disulphide, by the action of sodium on benzaldehyde or benzal chloride, by distilling fumaric and cinnamic phenyl esters:

+C 6 H 6 -CH :CH-C 6 H 6 (Ber., i8,p. 1945), and fromchlor asymmetrical diphenylethane derivatives which undergo a rearrangement when heated (Ber., 7. p. 1409). Stilbene (from Gr. <rrtX/3eu> > to glisten) crystallizes in large, colourless, glistening monoclinic plates, which melt at 124 and boil at 306. On passing the vapour through red-hot tubes it yields anthracene and toluene. Reduction with hydriodic acid gives dibenzyl, and heating with sulphur gives tetraphenylthiophene or thionessal. Many derivatives are known, some of which exist in two structural forms, exhibiting geometrical isomerism after the mode of fumaric and maleic acids. Those substituted in the benzene nucleus are obtained by condensing two molecules of a substituted benzyl and benzal chlorides. The diortho and dipara dinitro compounds result from the action of alcoholic potash on ortho- and para-nitrobenzyl chlorides. The latter on reduction yields a diamino compound, the disulphonic acid of which on diazotization and coupling with a phenol, etc., gives valuable substantive cotton dyes after the type yielded by Benzidine. Stilbene bromide when treated with alcoholic potash gives diphenyl acetylene or tolane, CeHs-CiC-CeHj.

Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)

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