The 1 5 diketones of this type, when heated with aqueous ammonia, form pyridine derivatives.
Certain a-diketones condense to form benzenoid quinones, two molecules of the diketone taking part in the reaction; thus diacetyl, CH 3 CO CO CH 3, yields p-xyloquinone, C 6 H 2 (CH 3) 2 0 2 (Ber., 1888, 21, p. 1411), and acetylpropionyl, CH 3 CO CO C 2 H 5, yields duroquinone, or tetramethylquinone, C 6 (CH 3) 4 0 2, Oxymethylene compounds, characterized by the grouping > C:CH(OH), also give benzene derivatives by hydrolytic condensation between three molecules; thus oxymethylene acetone, or formyl acetone, CH 3 CO.
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.