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Originally appearing in Volume V15, Page 763 of the 1911 Encyclopedia Britannica.
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DIKETONES.—The diketones contain two carbonyl groups, and are distinguished as a or 1.2 diketones, (3 or 1.3 diketones, 7 or 1.4 diketones, &c., according as they contain the groupings -CO. CO-, -CO. CH2•CO-,-CO•CH2•CH2•CO-, &c. The a-diketones may be prepared by boiling the product of the action of alkaline bisulphites on isonitrosoketones with 15 % sulphuric acid (H. v. Pechmann, Ber.,1887, 20, p. 3112 ; 1889, 22, p. 2115), CH3.CO.0 :(N•OH)•CH3 CH3.CO.0 :(NHSO3) •CH3 ->CH3-CO--CO.CH3; or by the action of isoamyl nitrite on the isonitrosoketones (O. Manasse, Ber., 1888, 21, P-2177), C2H6•CO•C :(NOH)•CH3-+nC6HONO= C2H6•CO•CO•CH3+C5HnOH+N20. They condense with orthodiamines to form quinoxalines (O. Hinsberg, Ann., 1887,237, p. 327), and with ammonia and aldehydes to form imidazoles. Diacetyl, CH3•CO•CO•CH3, is a yellowish green liquid,which boils at 87-88°C., and possesses a pungent smell. It combines with sodium bisulphite and with hydrocyanic acid. Dilute alkalis convert it into paraxyloquinone. The -diketones form characteristic copper salts, and in alcoholic solution they combine with semicarbazide to form products which on boiling with ammoniacal silver nitrate solution give pyrazoles (T. Posner, Ber., 1901, 34, p. 3975); with hydroxylamine they form isoxazoles, and with phenylhydrazine pyrazoles. Acetyl acetone, CH3•CO•CH2•CO•CH3, may be prepared by the action of aluminium chloride on acetyl chloride, or by condensing ethyl acetate with acetone in the presence of sodium (L. Claisen). It is a liquid of boiling point 136° C. It condenses readily with aniline to give ay-dimethyl quinoline. The 7-diketones are characterized by the readiness with which they yield furfurane, pyrrol and thiophene derivatives, the furfurane derivatives being formed by heating the ketones with a de-4 hydrating agent, the thiophenes by heating with phosphorus pentasulphide, and the pyrrols by the action of alcoholic ammonia or amines. Acetonylacetone,CH3•CO•CH2•CH2•CO•CH3,aliquid boiling at 194° C., may be obtained by condensing sodium aceto-acetate with mono-chloracetone (C. Paal, Ber., 1885, 18, p. 59), CH 3000H2C1+Na•CH •COCH3(COOR) - > CH3CO•CH2•CH •COCH3(COOR) — CH3CO•CH2•CH2•000H3; or by the hydrolysis of diaceto-succinic ester, prepared by the action of iodine on sodium aceto-acetate (L. Knorr, Ber., 1889, 22, pp. 169, 2100). 1.5 diketones have been prepared by L. Claisen by condensing ethoxymethylene aceto-acetic esters and similar compounds with 0-ketonic esters and with 1.3 diketones. The ethoxymethylene aceto-acetic esters are prepared by condensing aceto-acetic ester with ortho-formic ester in the presence of acetic anhydride (German patents 77354, 79087, '79863). The 1.5 diketones of this type, when heated with aqueous ammonia, form pyridine derivatives. Those in which the keto groups are in combination with phenyl residues give pyridine derivatives on treatment with hydroxylamine, thus benzamarone, C6H5CH[CH(C6H5)•C0•C6H5], gives pentaphenylpyridine, NC5(CBH5)5. On the general reactions of the 1.5 diketones, see E. Knoevenagel (Ann., 1894, 281, p. 25 et seq.) and H. Stobbe (Ber., 1902, 35, p. 1445). Many cyclic ketones are known, and in most respects they resemble the ordinary aliphatic ketones (see POLYMETHYLENES; TERPENES).
End of Article: DIKETONES
DIKE, or DYKE (Old Eng. dic, a word which appears i...

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