Which resonance structure for the SCN ion and the COS molecu

Which resonance structure for the SCN- ion and the COS molecule would you expect to be more stable? Explain.

Solution

ANSWER

:::S-C?N: resonance with ::S=C=N::

Thiocyanate (also known as rhodanide) is the anion [SCN]^?. It is the conjugate base of thiocyanic acid. Common derivatives include the colourless salts potassium thiocyanate and sodium thiocyanate. Organic compounds containing the functional group SCN are also called thiocyanates.Mercury(II) thiocyanate was formerly used in pyrotechnics.

Thiocyanate is analogous to the cyanate ion, [OCN]^?, wherein oxygen is replaced by sulfur. [SCN]^? is one of the pseudohalides, due to the similarity of its reactions to that of halide ions. Thiocyanate used to be known as rhodanide (from a Greek word for rose) because of the red colour of its complexes with iron. Thiocyanate is produced by the reaction of elemental sulfur or thiosulfate with cyanide:

The second reaction is catalyzed by the enzyme sulfotransferase known as rhodanase and may be relevant to detoxification of cyanide in the body.