Thiocyanic acid

  • Hydrogenthioncyanid
  • Rhodan acid
  • Rhodan hydrochloric acid

Oily, colorless liquid with a pungent odor

Liquid

2.04 g · cm -3

5 ° C

  • Readily soluble in water
  • Soluble in ethanol and diethyl ether

Attention

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Thiocyanic (obsolete: hydrogen thiocyanate acid) is an unstable chemical compound with the formula HSCN. It is the sulfur analog of cyanic acid HOCN. Its salts and esters are called thiocyanates.

Representation

The preparation of thiocyanic acid can be effected by reaction of hydrogen sulfide with mercury (II ) cyanide. The preparation of aqueous solutions of the acid is carried out conveniently by the decomposition of an aqueous solution of ammonium thiocyanate with dilute sulfuric acid.

Properties

Thiocyanic acid is a colorless, volatile compound that has a melting point of 5 ° C. It is readily soluble in water and a few organic solvents. Thiocyanic acid is unstable and stable only at low temperatures. So very dilute aqueous solutions of the acid decompose slowly at 0 ° C. As decomposition products hydrogen cyanide and Perthiocyansäure.

Thiocyanic (left ) is in a tautomeric equilibrium with the isothiocyanic (right ), the equilibrium is on the left side, so when thiocyanic:

Furthermore, there's the Thiazirin ( a sulfur derivative of the azirine ) a heterocyclic Thiocyansäureisomer, which can occur as intermediates:

CAS registry number Dangerous Substances Directive (67/548/EEC) Chemical reaction Chemical equilibrium
401278
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