Fulminic acid

Fulminic acid is an acid with the formula HCNO, more specifically Template:Chem2. It is an isomer of isocyanic acid (Template:Chem2) and of its elusive tautomer, cyanic acid (Template:Chem2), and also of isofulminic acid (Template:Chem2).<ref name=beck1966/>

Fulminate is the anion Template:Chem2 of any of its salts. For historical reasons, the fulminate functional group is understood to be Template:Chem2 as in isofulminic acid;<ref name=went1981>Template:Cite journal</ref> whereas the group Template:Chem2 is called nitrile oxide.

History

This chemical was known since the early 1800s through its salts and via the products of reactions in which it was proposed to exist,<ref name="JChemEd-history"/> but the acid itself was not detected until 1966.<ref name=beck1966>Template:Cite journal</ref>

Structure

Fulminic acid was long believed to have a structure of H–O–N⁺≡C⁻. It wasn't until the 1966 isolation and analysis of a pure sample of fulminic acid that this structural idea was conclusively disproven.<ref name="JChemEd-history">Template:Cite journal</ref> The chemical that actually has that structure, isofulminic acid (a tautomer of the actual fulminic acid structure) was eventually detected in 1988.<ref name="JChemEd-history"/>

The structure of the molecule has been determined by microwave spectroscopy with the following bond-lengths - C-H: 1.027(1) Å, C-N: 1.161(15) Å, N-O: 1.207(15) Å.<ref>Template:Cite journal</ref>

Synthesis

A convenient synthesis involves flash pyrolysis of certain oximes. In contrast to earlier syntheses, this method avoids the use of highly explosive metal fulminates.<ref>Template:Cite journal</ref>