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.