Therefore, it is catalysed
by a base and  the generated cyanide ion (CN
being a stronger nucleophile readily adds to-)
carbonyl compounds to yield corresponding
cyanohydrin Cyanohydrins 
are 
useful 
synthetic
intermediates (b) Addition of sodium hydrogensulphite: Sodium
hydrogensulphite adds to aldehydes and
ketones to form the addition products The position of
the equilibrium
lies largely to
the right hand
side for most
aldehydes and to
the left for most
ketones due to steric reasons