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−).[1]
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| Names | |
|---|---|
| IUPAC name Oxidoazaniumylidynemethane | |
| Identifiers | |
3D model (JSmol) | |
| 1071209 | |
| ChEBI | |
| ChEMBL | |
| ChemSpider | |
| 772 | |
PubChem CID | |
CompTox Dashboard (EPA) | |
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| Properties | |
| HCNO | |
| Molar mass | 43.02 g mol−1 |
| Conjugate base | Fulminate |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |
Fulminate is the anion [C−≡N+−O−] or any of its salts. For historical reasons, the fulminate functional group is understood to be −O−N+≡C− as in isofulminic acid;[2] whereas the group −C≡N+O− 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,[3] but the acid itself was not detected until 1966.[1]
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.[3] The chemical that actually has that structure, isofulminic acid (a tautomer of the actual fulminic acid structure) was eventually detected in 1988.[3]
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.[4]
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.[5]