Fulminic acid

Fulminic acid is an acid with the formula HCNO, more specifically H−C≡N⁺−O⁻. It is an isomer of isocyanic acid (H−N=C=O) and of its elusive tautomer, cyanic acid (H−O−C≡N), and also of isofulminic acid (H−O−N⁺≡C⁻).

Fulminate is the anion [C⁻≡N⁺−O⁻] of any of its salts. For historical reasons, the fulminate functional group is understood to be −O−N⁺≡C⁻ as in isofulminic acid; whereas the group −C≡N⁺O⁻ is called nitrile oxide.