Question

Question. Synthesize from benzene. (Hint: Some of these require diazonium ions.)

1. 4-methylaniline
2. 3-ethylphenol
3. 2-ethyl-5-hydroxybenzoic acid
4. 4-ethoxyaniline

Short answer

Benzene on reaction with methyl chloride in presence of aluminum chloride undergoes Friedel-Crafts alkylation reaction and forms toluene. Toluene on reaction with concentrated sulphuric acid and nitric acid undergoes nitration and nitro group gets introduced at para position due to directive influence of methyl group. Further, on reduction with tin and hydrogen chloride mixture, nitro group gets reduced to amino group and required product gets formed.

Formation of the product

Step-by-step solution

Step-1. Explanation of part (a):

Benzene on reaction with methyl chloride in presence of aluminum chloride undergoes Friedel-Crafts alkylation reaction and forms toluene. Toluene on reaction with concentrated sulphuric acid and nitric acid undergoes nitration and nitro group gets introduced at para position due to directive influence of methyl group. Further, on reduction with tin and hydrogen chloride mixture, nitro group gets reduced to amino group and required product gets formed.

Formation of the product

Step-2. Explanation of part (b):

Benzene on reaction with acetyl chloride in presence of aluminium chloride undergoes Friedel-Crafts acylation reaction which forms a product which further on nitration reaction forms product in which nitro group is at meta position to the acetyl group due to directive influence of acetyl group. On clemmenson reduction, both ketonic as well as nitro group gets reduced and further on reaction with sodium nitrite and hydrogen chloride, diazonium ion forms which on hydrolysis forms the required product.

Formation of the product

Step-3. Explanation of part (c):

Benzene on reaction with ethyl iodide in presence of aluminium chloride undergoes Friedel-Crafts alkylation reaction which forms a product which on sulphonation forms a product in which group gets introduced at para position to ethyl group due to directive influence of ethyl group. Further, on nitration, nitro group gets introduced at ortho position to ethyl group as ethyl group is ortho and para directing. On hydrolysis, desulphonation occurs and further reduction with iron and hydrogen chloride mixture yields product in which amino group is present at ortho position to ethyl group.
On reaction with sodium nitrite and hydrogen chloride, diazonium ion forms which on reaction with copper(I) cyanide forms product. On hydrolysis and nitration reaction, a product is formed in which nitro group is at para position of the ethyl group and carboxylic group is at ortho position of ethyl group. Further reaction with iron and hydrogen chloride and sodium nitrite, hydrogen chloride mixture, diazonium ion forms which on hydrolysis yields a required product.


Formation of the product

Step-4. Explanation of part (d):

Benzene on nitration forms nitrobenzene which on further reduction with iron and hydrogen chloride mixture, forms aminobenzene. On treatment with sodium nitrite and hydrogen chloride followed by hydrolysis, phenol is obtained which on reaction with base such as sodium hydroxide forms phenoxide ion and further reaction with ethyl iodide, we get ethoxybenzene as the product. Further nitration and reduction with iron and hydrogen chloride mixture, we get the required product.

Formation of the product