Dicyandiamide.Calcium cyanamide can be used as a pesticide intermediate
For many years the most important commercial process was via heating dicyanodiamide ([dicy"), either with ammonia or on its own, under pressure. The [dicy" is prepared by heating cyanamide solution at 70–80 °C. The cyanamide itself is prepared from calcium cyanamide:
Heated [dicy" to just above its melting point (209 °C) results in a vigorous exothermic reaction, producing some melamine and ammonia together with a number of complex water-insoluble deammoniation products:
In order to achieve a high yield of melamine in the commercial process, the reaction is carried out in the presence of ammonia at about 300 °C under pressure.