Write short note on ammonolysis.

Explanation

Hoffmann.s Ammonolysis. Alkyl halides (generally `1^(@)`) react with alcoholic ammonia to form primary, secondary and tertiary amines alongwith some quaternary ammonium salts. The reaction is carried out by heating alkyl halide (preferably iodide) with an alcoholic solution of ammonia in a sealed tube at 370 K. This reaction is called ammonolysis.
If ammonia is uses in excess, `1^(@)` amine is the major product.
`underset("Alkylhalide")(RX)+2overset(..)(NH_(3))rarrunderset(1^(@)"Amine")(Roverset(..)NH_(2))+NH_(4)^(+)X^(-)`
`underset("Ethyliodide")(C_(2)H_(5)I)+2NH_(3)rarrunderset("Ethylamine")(C_(2)H_(5)NH_(2))+NH_(4)^(+)I^(-)`
If alkyl halide is used in excess, the primary amine so formed further reacts with alkyl halide to form secondary amine, tertiary amine and finally quaternary ammonium salt.
`underset(1^(@)"Amine")(Roverset(..)(N)H_(2))+RXrarrunderset(2^(@)"Amine")(R_(2)overset(..)NH)+HX`
`underset(2^(@)"Amine")(R_(2)overset(..)(N)H)+RXrarrunderset(3^(@)"Amine")(R_(3)overset(..)N)+HX`
`underset(3^(@)"Amine")(R_(3)overset(..)N)+RXrarrundersetunderset("ammonium salt")("Quaternary")([R_(4)N]^(+)X^(-))`
The actual composition of reaction mixture depends upon the molar concentrations of the alkyl halide and ammonia used. However, the mixture obtained is very complex and difficult to separate in the laboratory. Therefore, this method is used only in the manufacture of amines.
Limitations. (1) This method is not suitable for the preparation of aryl since aryl halides are much less reactive than alkyl halides towards nucleophilic substitution reactions.
(2) As this method does not give a single amine, but a mixture of amines, it is very difficult to separate the mixture in the laboratory.