Hydrogen cyanide is a linear molecule, with a triple bond between carbon and nitrogen. The tautomer of HCN is HNC, hydrogen isocyanide.
Hydrogen cyanide is weakly acidic with a pK of 9.2. It partially ionizes in water to give the cyanide anion, CN. A solution of hydrogen cyanide in water, represented as HCN, is called hydrocyanic acid. The salts of the cyanide anion are known as cyanides.
HCN has a faint bitter almond-like odor that some people are unable to detect owing to a recessive genetic trait. The volatile compound has been used as inhalation rodenticide and human poison, as well as for killing whales. Cyanide ions interfere with iron-containing respiratory enzymes.