Question

Question: Synthesize each compound from benzene. Use a diazonium salt as one of the synthetic intermediates.

Short answer

Answer

Step-by-step solution

Friedel-Craft Alkylation

The organic reaction involving the introduction of an alkyl group to an aromatic compound by the reaction with an alkyl halide in the presence of anhydrous aluminum chloride is known as the ‘Friedel-Craft Alkylation’ reaction.

a.Benzene reacts with methyl chloride in the presence of anhydrous aluminum chloride to form toluene.

Formation of tolueneb. Benzene reacts with ethyl chloride in the presence of anhydrous aluminum chloride to form ethylbenzene.

Formation of ethylbenzene

Nitration

The organic reaction involving the replacement of a hydrogen atom by a nitro group by reacting with a mixture of concentrated nitric acid and sulphuric acid is known as the ‘nitration’ reaction.

a. Toluene reacts with the nitrating mixture to form -ortho and -para nitro toluene. The compound is reduced to form the corresponding amine.

Formation of toluidine

b. Ethyl benzene reacts with the nitrating mixture to form the corresponding -ortho and para nitro toluene. Then it is reduced to convert the nitro group to the amino group.

Formation of p-ethylaniline

c. Benzene is nitrated to form the corresponding major product p-nitrobenzene.

Nitration of benzene ring

Diazotization

The reaction by which aromatic amines react with aqueous acid of sodium nitrate in the presence of any mineral acid to form diazonium salt is known as the diazotization reaction.

a. The p-toluidine is treated with sodium nitrate and HCl to form the diazotization salt.

Formation of diazotisation salt

b. The substituted amine is treated with sodium nitrate and HCl to form the diazotization salt.

Formation of diazotisation salt

c. The benzene is treated with a nitrating mixture to form the corresponding nitro benzene.

Formation of Cyanides

a. The diazotisation salt is treated with cuprous cyanide to form the corresponding cyano- compound which is reduced to form the required compound.

Formation of the required compound.

b. The diazotisation salt is treated with cuprous cyanide to form the corresponding cyano- compound which is acid-hydrolyzed to form the required compound.

Formation of required compound

Chlorination

c. The nitro- compound is chlorinated with two equivalents of chlorine in the presence of ferric chloride to form 3,5-dichloronitrobenzene.

Chlorination of benzene ring

The compound is reduced and converted to a diazotization salt followed by treatment with aniline to form the required compound.

Formation of product