Ncert Exercises & Solutions

Which of the following methods of preparation of amines will not give the same number of carbon atoms in the chain of amines as in the reactant?

1.	Reaction of nitrile with LiAlH₄
2.	Reaction of amide with LiAlH₄ followed by treatment with water
3.	Heating alkyl halide with potassium salt of phthalimide followed by hydrolysis
4.	Treatment of amide with bromine in an aqueous solution of sodium hydroxide.

Hint: Follow Hoffmann bromamide reaction

1. Aliphatic and aryl primary amines can be easily prepared by the reduction of the corresponding nitriles with LiAlH₄.

The reaction is as follows:

In this reaction, starting compound and product both contains the same number of the carbon atom.

2.
When amide undergoes a reduction reaction with LiAlH₄ followed by a reaction with water, then amine is obtained as a product. The reaction is as follows:

In this reaction, starting compound and product both contains the same number of the carbon atom.

3.
When alkyl halide with potassium salt of phthalimide followed by hydrolysis gives amine as a product.
This process is known as Gabriel phthalimide reaction. The number of carbon atoms in the chain of amines of the product is the same as the reactant.

The reaction is as follows:

4.
The fourth reaction is an example of the Hoffmann bromamide reaction. Preparation of primary amines by treating an amide with bromine in an aqueous or ethanolic solution of sodium hydroxide.

The amine so formed contains one carbon less than that present in the amide.

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