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| Names | |||
|---|---|---|---|
| IUPAC name Nitridosulfanidocarbon[3] | |||
Other names
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| Identifiers | |||
3D model (JSmol) | |||
| 3DMet | |||
| ChEBI | |||
| ChEMBL | |||
| ChemSpider | |||
| ECHA InfoCard | 100.006.672  | ||
| EC Number |
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Gmelin Reference | 25178 | ||
| KEGG | |||
| MeSH | thiocyanic+acid | ||
PubChem CID | |||
| UNII | |||
CompTox Dashboard (EPA) | |||
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SMILES
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| Properties | |||
Chemical formula | CHNS | ||
| Molar mass | 59.09 g·mol−1 | ||
| Appearance | colorless, oily liquid | ||
| Odor | pungent | ||
| Density | 2.04 g/cm3 | ||
| Melting point | 5 °C (41 °F; 278 K) | ||
| Miscible | |||
| Solubility | soluble in ethanol, diethyl ether | ||
| log P | 0.429 | ||
| Acidity (pKa) | 0.926 | ||
| Basicity (pKb) | 13.071 | ||
| Hazards | |||
EU classification (DSD) (outdated) | ){kind=small} Xn | ||
| R-phrases (outdated) | R20/21/22, R32, R52/53 | ||
| S-phrases (outdated) | (S2), S13 | ||
| Related compounds | |||
Related alkanenitriles |
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |||
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)
Thiocyanic acid is a chemical compound with the formula HSCN which exists as a tautomer with isothiocyanic acid (HNCS).[4] The iso- form tends to dominate with the material being about 95% isothiocyanic acid in the vapor phase.[5]
Tautomerism between thiocyanic acid (left) and isothiocyanic acid (right)
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It is a weak acid, bordering on strong, with a pKa of 1.1 at 20 °C and extrapolated to zero ionic strength.[6]
HSCN is predicted to have a triple bond between carbon and nitrogen. It has been observed spectroscopically but has not been isolated as a pure substance.[7]
The salts and esters of thiocyanic acid are known as thiocyanates. The salts are composed of the thiocyanate ion (−SCN) and a suitable metal cation (e.g., potassium thiocyanate, KSCN). The esters of thiocyanic acid have the general structure R–SCN.
Isothiocyanic acid, HNCS, is a Lewis acid whose free energy, enthalpy and entropy changes for its 1:1 association with a variety of Lewis bases in carbon tetrachloride solution at 25°C have been reported.[8] HNCS acceptor properties are discussed in the ECW model.
References
- ^ Merck Index, 11th Edition, 9257.
- ^ Richter, Victor von; Spielmann, Percy E., trans. (1922). Organic Chemistry or Chemistry of the Carbon Compounds. vol. 1. Philadelphia, Pennsylvania, U.S.A.: P. Blakiston's Son & Co. p. 466.
- ^ "thiocyanic acid (CHEBI:29200)". Chemical Entities of Biological Interest. USA: European Bioinformatics Institute. 18 October 2009. Main. Retrieved 5 June 2012.
- ^ Holleman, A. F.; Wiberg, E. (2001). Inorganic Chemistry. San Diego: Academic Press. ISBN 0-12-352651-5.
- ^ Beard, C. I.; Dailey, B. P. (1950). "The Structure and Dipole Moment of Isothiocyanic Acid" (PDF). The Journal of Chemical Physics. 18 (11): 1437. Bibcode:1950JChPh..18.1437B. doi:10.1063/1.1747507. hdl:1721.1/4934.
- ^ Martell, A. E.; Smith, R. M.; Motelaitis, R. J. (2001). NIST Database 46. Gaithersburg, MD: National Institute of Standards and Technology.
- ^ Wierzejewska, M.; Mielke, Z. (2001). "Photolysis of Isothiocyanic Acid HNCS in Low-Temperature Matrices. Infrared Detection of HSCN and HSNC Isomers". Chemical Physics Letters. 349 (3–4): 227–234. Bibcode:2001CPL...349..227W. doi:10.1016/S0009-2614(01)01180-0.
- ^ . Barakat, T. M.; Nelson, J.; Nelson, S. M.; Pullin, A. D. E. (1969.) “Spectra and hydrogen-bonding of characteristics of thiocyanic acid. Part 4.—Association with weak proton acceptors”. Trans. Faraday Soc., 1969,65, 41-51