Sodium thiocyanate

8 NaCN + S₈ → 8 NaSCN

Sodium thiocyanate crystallizes in an orthorhombic cell. Each Na⁺ center is surrounded by three sulfur and three nitrogen ligands provided by the triatomic thiocyanate anion. It is commonly used in the laboratory as a test for the presence of Fe³⁺ ions.

Applications in chemical synthesis

Sodium thiocyanate is employed to convert alkyl halides into the corresponding alkylthiocyanates. Closely related reagents include ammonium thiocyanate and potassium thiocyanate, which has twice the solubility in water. Silver thiocyanate may be used as well; the precipitation of insoluble silver halides help simplify workup. Treatment of isopropyl bromide with sodium thiocyanate in a hot ethanolic solution affords isopropyl thiocyanate. Protonation of sodium thiocyanate affords isothiocyanic acid, S=C=NH (pK_a = −1.28). This species is generated in situ from sodium thiocyanate; it adds to organic amines to afford derivatives of thiourea.