Primary amines
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Outline the reduction of a nitrile to form a primary amine.
Nitriles can be reduced to primary amines using reducing agents like LiAlH₄ in dry ether, followed by dilute acid hydrolysis, or by catalytic hydrogenation using a nickel catalyst and H₂ at high temperature and pressure.
Describe the reaction of a halogenoalkane with excess ammonia to produce a primary amine.
A halogenoalkane reacts with excess ethanolic ammonia via nucleophilic substitution. The ammonia acts as a nucleophile, replacing the halogen. Excess ammonia is used to minimize further substitution of the primary amine formed.
What type of reaction is the formation of an amine from a halogenoalkane and ammonia?
This is a nucleophilic substitution reaction. The lone pair on the nitrogen of ammonia acts as a nucleophile, attacking the partially positive carbon bonded to the halogen.
Why is excess ammonia used in the reaction of halogenoalkanes with ammonia to produce primary amines?
Excess ammonia is used to minimize further substitution of the primary amine product. The primary amine itself is also nucleophilic and can react with the halogenoalkane, leading to secondary and tertiary amines and quaternary ammonium salts.
What are the reagents and conditions for reducing a nitrile to a primary amine?
Reagents: Lithium aluminium hydride (LiAlH₄) in dry ether, followed by dilute acid hydrolysis; OR catalytic hydrogenation (H₂) with a nickel catalyst at high temperature and pressure.
Write a balanced chemical equation for the reduction of ethanenitrile to ethylamine using LiAlH₄.
CH₃CN + 4[H] → CH₃CH₂NH₂. The reducing agent, LiAlH₄, provides the hydrogen atoms [H] needed for the reduction.
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