Nitriles are organic compounds that have the general formula RCN (RC≡N).
Nitriles can be prepared by a substitution reaction using KCN.
The –:C≡N: ion is a good carbon nucleophile, and this substitution results in extension of the carbon chain.
This means that both a nitrile and an amide are converted to carboxylic acid by hydrolysis with aqueous acid.
Ammonium ion (NH4+) is a co-product of the reaction for both nitriles and primary amides (those having only hydrogen on the nitrogen).
Reactions 1 and 2 can be combined to convert a haloalkane to a carboxylic acid having an additional carbon atom.
Note that the overall process corresponds to introducting a CO2H group at the carbon originally bearing the halogen.
Nitriles can be prepared by a substitution reaction using KCN.
The –:C≡N: ion is a good carbon nucleophile, and this substitution results in extension of the carbon chain.
Reaction 1: CH3CH2Br + –:C≡N: 
CH3CH2C≡N: + Br–
The nitrile functional group is on the same oxidation level as carboxylic acids and amides which also have three bonds from carbon to more electronegative atoms. CH3CH2C≡N: + Br–This means that both a nitrile and an amide are converted to carboxylic acid by hydrolysis with aqueous acid.
| Reaction 2: CH3CH2C≡N | H3O+  |  |
Reaction 3:  | H3O+ |
Ammonium ion (NH4+) is a co-product of the reaction for both nitriles and primary amides (those having only hydrogen on the nitrogen).
Reactions 1 and 2 can be combined to convert a haloalkane to a carboxylic acid having an additional carbon atom.
Note that the overall process corresponds to introducting a CO2H group at the carbon originally bearing the halogen.
CH3CH2Br CH3CH2CN CH3CH2CO2H
CH3CH2CN CH3CH2CO2H