Carbon Nitrides

Besides cyanogen, to be described below, carbon is known to form two other nitrides, C₄N₂ and C₆N₂, which have recently been obtained from organic sources.

Carbon Subnitride, C₄N₂, is dicyanacetylene, NC-C≡C-CN, and the nitrile of acetylene dicarboxylic acid; it is formed by the elimination of two molecules of water from the amide of that acid:

NH₂-CO-C≡C-CO-NH₂ = NC-C≡C-CN + 2H₂O,

is crystalline, melts at 20.5°-21° C., and boils at 76° C. under 753 mm. pressure.

Another subnitride, C₆N₂, is probably the nitrile of diacetylene dicarboxylic acid, and thus has the constitution NC-C≡C-C≡C-CN. It is prepared by oxidising cyanacetylene, CH≡C-CN, with potassium ferricyanide, and forms crystalline needles melting at 64° C.