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Encyclopedia Britannica

DIKETONES

This article appears in Volume V15, Page 763 of the Encyclopedia Britannica.

Encyclopedia Britannica - Main :: DEM-DIO

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. CH2CO-,-COCH2CH2CO-, &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 :(NOH)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), C2H6COC :(NOH)CH3-+nC6HONO= C2H6COCOCH3+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, CH3COCOCH3, is a yellowish green liquid,which boils at 87-88C., 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

HYDROXYLAMINE, NH2OH

they form isoxazoles, and with phenylhydrazine pyrazoles. Acetyl

acetone

ACETONE, or DIMETHYL KETONE

, CH3COCH2COCH3, may be prepared by the action of

aluminium

ALUMINIUM (symbol Al; atomic weight 27.0)

chloride on acetyl chloride, or by condensing

ethyl

ETHYL

acetate with

acetone

ACETONE, or DIMETHYL KETONE

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

QUINOLINE (Benzopyridine), C9H7N

.
The 7-diketones are characterized by the readiness with which they yield furfurane, pyrrol and thiophene derivatives, the furfurane derivatives being formed by

heating

HEATING

the ketones with a de-4 hydrating agent, the thiophenes by

heating

HEATING

with phosphorus pentasulphide, and the pyrrols by the action of alcoholic ammonia or amines. Acetonylacetone,CH3COCH2CH2COCH3,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+NaCH COCH3(COOR)
- > CH3COCH2CH COCH3(COOR)
CH3COCH2CH2000H3;
or by the

hydrolysis

HYDROLYSIS (Gr. 6Swp, water, Anew, to loosen)

of diaceto-succinic ester, prepared by the action of

iodine

IODINE (symbol I, atomic weight '26.92)

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

PYRIDINE

derivatives. Those in which the keto groups are in combination with phenyl residues give

pyridine

PYRIDINE

derivatives on treatment with

hydroxylamine

HYDROXYLAMINE, NH2OH

, thus benzamarone, C6H5CH[CH(C6H5)C0C6H5], 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

ORDINARY (med. Lat. ordinarius, Fr. ordinaire)

aliphatic ketones (see POLYMETHYLENES; TERPENES).

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