How do you convert the following:

(i) Aniline to benzene.

(ii) Ethanamide to methamine.

(iii) Nitrobenzene to aniline.

OR

Write the chemical equations involved when C₂H₅NH₂ is treated with the following reagents:

(i) CH₃COCl/pyridine

(ii) C₆H₅SO₂Cl

(iii) CHCl₃ + KOH

(i) Aniline to benzene

Aniline has a nitrogen atom which contains a lone pair that produces resonance effect making the C ─ N stronger and harder to break. So first it is necessary to make it a weaker base which can be done by converting it into diazonium salt. When aniline is treating with nitrating mixture or sodium nitrate in presence of a mineral acid like HCl, it results into benzene diazonium salt.

This benzene diazonium salt is made to react with phosphinic acid to undergo reduction in presence of a metal like Cu or Zn to enhance the speed of the reaction.

NOTE: A secondary alternative is available. When diazonium salt is treated with alcoholic KOH it gives phenol which can then be reduced in presence of Zn to give benzene. But this involves three steps to give our product while the suggested above reaction requires two steps.

(ii) ethanimide to ethaneamine

Amides on reduction with lithium aluminium hydride in completely dry atmosphere reduce the amide which on hydrolysis in second step yields an amine.

(iii) nitrobenzene to aniline

Nitrobenzene can be reduced by di-hydrogen in presence of finely divided nickel, palladium or platinum to provide surface reaction area and ethanol. The reduction can also be done on treatment with HCl and Sn.

OR

Option (i) ethyl amine when treated with CH₃COCl and pyridine, ethonyl chloride adds on two molecules of ethyl amine to give an amine salt and substituted amide.

Rxn:

HCl is also formed but not in major quantity so is not included in the reaction.

Option (ii) ethylamine being a base when treated with C₆H₅SO₂Cl (Hinsberg’s reagent) reacts to form sulphonamides.

Option (iii) when ethane is treated with chloroform it undergoes carbylamine reaction to form isocyanides under hydroxide conditions. This is also called as isocyanides test to determine the presence of primary alcohol as isocyanides have specific odour which can be used for identification.

Rxn: