Thiocyanic acid

From Wikipedia, the free encyclopedia
  (Redirected from Isothiocyanic acid)
Jump to: navigation, search
Thiocyanic acid[1]
Skeletal formula of thiocyanic acid
Skeletal formula of thiocyanic acid with the explicit hydrogen added
Spacefill model of thiocyanic acid
IUPAC name
Other names
463-56-9 YesY
3DMet B00344
ChEBI CHEBI:29200 YesY
ChemSpider 760 YesY
EC Number 207-337-4
Jmol interactive 3D Image
KEGG C01755 N
MeSH thiocyanic+acid
PubChem 781
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)
Solubility soluble in ethanol, diethyl ether
log P 0.429
Acidity (pKa) 0.926
Basicity (pKb) 13.071
Harmful Xn
R-phrases R20/21/22, R32, R52/53
S-phrases (S2), S13
Related compounds
Related alkanenitriles
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is YesYN ?)
Infobox references

Thiocyanic acid is a chemical compound with the formula HSCN that exists as a mixture with the isomeric compound isothiocyanic acid (HNCS).[3] It is the sulfur analog of cyanic acid (HOCN).

It is a weak acid, bordering on strong, with a pKa of 1.1 at 20 °C and extrapolated to zero ionic strength.[4]

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.[5]

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.


  1. ^ Merck Index, 11th Edition, 9257.
  2. ^ "thiocyanic acid (CHEBI:29200)". Chemical Entities of Biological Interest. USA: European Bioinformatics Institute. 18 October 2009. Main. Retrieved 5 June 2012. 
  3. ^ Holleman, A. F.; Wiberg, E. Inorganic Chemistry Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
  4. ^ Martell, A. E.; Smith, R. M.; Motelaitis, R. J. NIST Database 46 National Institute of Standards and Technology: Gaithersburg, MD, 2001.
  5. ^ 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: 227–234. doi:10.1016/S0009-2614(01)01180-0.