Question

Which of the following methods of preparation of amines will give same number of carbon atoms in the chain of amines as in the reactant?

Options

• Reaction of nitrite with \[\ce{LiAlH4}\].

• Reaction of amide with \[\ce{LiAlH4}\] followed by treatment with water

• Heating alkyl halide with potassium salt of phthalimide followed by hydrolysis.

• Treatment of amide with bromine in aqueous solution of sodium hydroxide.

Answer 1

Heating alkyl halide with potassium salt of phthalimide followed by hydrolysis.

Explanation:

Aliphatic and arylalkyl primary amines can be prepared by the reduction of the corresponding nitriles with \[\ce{LiAlH4}\].

\[\ce{\underset{Alkynitrite}{R - C ≡ N} \underset{Arynitrite}{Ar - C ≡ N} -> LiAlH4   RCH2\underset{1° amine}{NH2} or ArCh2NH2}\]

Heating alkyl halide with primary, secondary and tertiary amine can be prepared by reduction of \[\ce{LiAlH4}\] followed by treatment with water.

\[\ce{\underset{1° amide}{R - CONH2} ->[(i) LiAlH4][(ii) H2O] R - CH2 - NH2}\]

Heating alkyl halide with potassium salt of phthalimide followed by hydrolysis produces primary amine. This process is known as Gabriel phthalimide reaction. The number of carbon atoms in the chain of amines of product is same as reactant.