The 1 5 diketones of this type, when heated with aqueous ammonia, form pyridine derivatives.
The carbonyl group by itself does not produce colour, but when two adjacent groups occur in the molecule, as for example in the a-diketones (such as di-acetyl and benzil), a yellow colour is produced.
Semicarbazide) with ortho-diketones (J.
Pechmann (Ber., 1888, 21, p. 1417) has shown that a-diketones are converted into paraquinones by the action of warm solutions of the caustic alkalis, diacetyl yielding para-xyloquinone: CH 3 CO CO CH 3 CH 3 C CO.
The orthoquinones more resemble the a-diketones; they are crystalline solids of a red or yellow colour, but differ from the paraquinones in being devoid of smell and not volatile in a current of steam.
-The diketones contain two carbonyl groups, and are distinguished as a or I.
2 diketones, 1 3 or 1.3 diketones, y or I.
4 diketones, &c., according as they contain the groupings -CO CO-, -CO.
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.
The -y-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 dehydrating agent, the thiophenes, by heating with phosphorus pentasulphide, and the pyrrols by the action of alcoholic ammonia or amines.
1.5 diketones have been prepared by L.
On the general reactions of the 1.5 diketones, see E.
5 diketones of the type inset, when heated with ammonia, also yield pyridine derivatives.
CH -CO CH2 from 1.5-diketones which contain a methyl group next the keto-group (W.
The thiophen homologues are best prepared by heating the 1.4 diketones with phosphorus pentasulphide, the diketones reacting in the enolic form: Thiotenol, or oxymethyl thiophene, is prepared by heating laevulinic acid with phosphorus pentasulphide (W.