Write down functional isomers of a carbonyl compound with molecular formula `C_(3)H_(6)O.` Which isomer will react faster with HCN and why? Explain the mechanism of the reaction also. Will the reaction lead to the completion with the conversion of whole reactant into product at reaction conditions? If a strong acid is added to the reaction mixture what will be the effect on concentration of the product and why?

Explanation

The two functional isomers for the carbonyl compound with molecular `C_(3)H_(6)O` are : `CH_(3)CH_(2)CHO` (proponal) and `CH_(3)COCH_(3)` (propanone)
`CH_(3)CH_(2)CHO` will react faster with HCN as compared to `CH_(3)COCH_(3)` because of less steric hindrance and less electron releasing +I effect. Since there is only one alkayl group present. For details, consult section 8.
The reaction is of reversible nature and will not proceed to completion under the reaction conditions.
The reaction is carried in basic medium which helps in generating `CN^(-)` ion needed for the nucleophile attack.
`HCN+OH^(-)rarrH_(2)O+CN^(-)` Since HCN itself is a weak acid, the addition of a strong acid will inhibit or retard the release of `CN^(-)` ion from HCN in the reaction mixture. The reaction will show down. For more details, Consult section 13.8.