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. |