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DIKETONES

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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 See also:

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 See also:action of alkaline bisulphites on isonitrosoketones with 15 % sulphuric See also:acid (H. v. Pechmann, Ber.,1887, 20, p. 3112 ; 1889, 22, p. 2115), See also: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 See also:form quinoxalines (O. Hinsberg, See also:Ann., 1887,237, p. 327), and with See also:ammonia and See also:aldehydes to form See also:imidazoles. Diacetyl, CH3•CO•CO•CH3, is a yellowish See also:green liquid,which boils at 87-88°C., and possesses a pungent See also:smell.

It combines with See also:

sodium bisulphite and with hydrocyanic acid. Dilute alkalis convert it into paraxyloquinone. The -diketones form characteristic See also:copper salts, and in alcoholic See also:solution they combine with semicarbazide to form products which on boiling with ammoniacal See also:silver nitrate solution give See also:pyrazoles (T. Posner, Ber., 1901, 34, p. 3975); with See also:hydroxylamine they form See also:isoxazoles, and with phenylhydrazine pyrazoles. Acetyl See also:acetone, CH3•CO•CH2•CO•CH3, may be prepared by the action of See also:aluminium chloride on acetyl chloride, or by condensing See also:ethyl acetate with acetone in the presence of sodium (L. Claisen). It is a liquid of boiling point 136° C. It condenses readily with See also:aniline to give ay-dimethyl See also:quinoline. The 7-diketones are characterized by the readiness with which they yield See also:furfurane, See also:pyrrol and thiophene derivatives, the furfurane derivatives being formed by See also:heating the See also:ketones with a de-4 hydrating See also:agent, the thiophenes by heating with See also:phosphorus pentasulphide, and the pyrrols by the action of alcoholic ammonia or See also: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 See also:

hydrolysis of diaceto-succinic ester, prepared by the action of See also: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 See also: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 (See also:German See also:patents 77354, 79087, '79863). The 1.5 diketones of this type, when heated with aqueous ammonia, form See also:pyridine derivatives. Those in which the keto groups are in See also:combination with phenyl residues give pyridine derivatives on treatment with hydroxylamine, thus benzamarone, C6H5CH[CH(See also:C6H5)•C0•C6H5], gives pentaphenylpyridine, NC5(CBH5)5. On the See also: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 See also:

ordinary aliphatic ketones (see See also:POLYMETHYLENES; See also:TERPENES).

End of Article: DIKETONES

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