Compounds that contain the cyanate functional group, −O−C≡N, are known as cyanates or cyanate esters. Aryl cyanates such are phenyl cyanate,  can be formed by a reaction of phenol with cyanogen chloride, ClCN, in the presence of a base.
Organic compounds that contain the isocyanate functional group −N=C=O are known as isocyanates. It is conventional in organic chemistry to write isocyanates with two double bonds, which accords with a simplistic valence bond theory of the bonding. In nucleophilic substitution reactions cyanate usually forms an isocyanate. Isocyanates are widely used in the manufacture of polyurethane products and pesticides; methyl isocyanate, used to make pesticides, was a major factor in the Bhopal disaster.