NCERT Solutions
Class 12 Chemistry
Amines
Q.8
Accomplish the following conversions:
(i) Nitrobenzene to benzoic acid
(ii) Benzene to m-bromophenol
(iii) Benzoic acid to aniline
(iv) Aniline to 2, 4, 6-tribromofluorobenzene
(v) Benzyl chloride to 2-phenylethanamine
(vi) Chlorobenzene to p-chloroaniline
(vii) Aniline to p-bromoaniline
(viii) Benzamide to toluene
(ix) Aniline to benzyl alcohol.
(i) Nitrobenzene to benzoic acid
First nitrobenzene is reduced to aniline by reduction with hydrogen gas with palladium catalyst followed by nitration and substitution and final hydrolysis by acid by a proton yields benzoic acid.
(ii) Benzene to m-bromophenol
Benzene by nitration with conc. hydrochloric acid and nitrous acid gives nitrobenzene which on reaction with bromine liquid gives m-bromobenzene.
Upon reduction with tin and acid followed by heating with diluted hydrochloric acid gives m-bromophenol.
(iii) Benzoic acid to aniline
Benzoic acid, reacted with sulphonyl chloride undergoes reaction, followed by ammine and bromine liquid in presence of sodium hydroxide gives aniline. This reaction is called as Hoffman bromamide degradation.
(iv) Aniline to 2, 4, 6-tribromofluorobenzene
Aniline reaction with bromine water, followed by sodium nitrite gives 2, 4, 6 - tribromodiazoniumchloride, which is very reactive, gives 2, 4, 6tribrmofluorobenzene upon treatment with hydrofluoroburic acid.
(v) Benzyl chloride to 2-phenylethanamine
Benzyl chloride reacted with alcoholic NaCN and reduction gives 3phenylethananmine.
(vi) Chlorobenzene to p-chloroaniline
Chlorobenzene upon nitration with nitronium ion and para product obtained undergoes reduction to give p-chloroaniline.
(vi) Aniline to p-bromoaniline
As aniline is a very activating group, it is first reacted with anhydride to make it less activating, which on reaction with bromine in acetic acid, followed by acid hydrolysis gives p-bromoaniline.
(viii) Benzamide to toluene
Benzamide undergoes Hoffman bromamide degradation to give aniline upon treatment with sodium nitrite gives benzenediazonium chloride, reacts with phosphoric acid , followed by Friedel crafts reaction with methyl chloride in solvent gives toluene.
(ix) Aniline to benzyl alcohol.
Aniline reacts with sodium nitrite following by substitution reaction with KCN, by acid hydrolysis gives benzoic acid which upon treatment with reducing agent gives benzyl alcohol.
