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Question
Answer the following
Explain the ammonolysis of alkyl halides.
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Solution
i. When alkyl halide is heated with an alcoholic solution of excess ammonia, it undergoes a nucleophilic substitution reaction in which the halogen atom is replaced by an amino (–NH2) group to form primary amine.
ii. This process of breaking of the C – X bond by ammonia is known as ammonolysis. The reaction is also known as the alkylation of ammonia. The reaction is carried out in a sealed tube at 373 K.
iii. The primary amine obtained in the1st step is stronger nucleophile than ammonia. Hence, it further reacts with an alkyl halide to form secondary and tertiary amines and finally quaternary ammonium salt if NH3 is not used in large excess.
\[\ce{\underset{\text{Alkyl halide}}{R - X} + \underset{\text{(excess)}}{NH3_{(alc.)}}->[\Delta] \underset{1^0}{R} - NH2 + HX}\]
iv. The order of reactivity of alkyl halides with ammonia is R–I > R–Br > R–Cl.
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