CBSE 2026 · Region 1 · Set 1 · Q29 · 4 marks
The reaction of amines with mineral acids to form ammonium salts shows that these are basic in nature. Aliphatic amines are stronger bases than ammonia whereas aromatic amines are weaker bases than ammonia. Aliphatic and aromatic primary and secondary amines react with acid chlorides, anhydrides and esters by nucleophilic substitution reaction. The main problem encountered during electrophilic substitution reactions of aromatic amines is that of their high reactivity. Substitution tends to occur at ortho-and para-positions. Hinsberg reagent is used for the identification and distinction between primary, secondary and tertiary amines. Aryldiazonium salts, usually obtained from arylamines, undergo replacement of the diazonium group with a variety of nucleophiles to provide advantageous methods for producing aryl halides, cyanides, phenols and arenes. Answer the following questions :(i)Why $\displaystyle \mathrm{CH}_{3}-\mathrm{NH}_{2}$ is a stronger base than $\displaystyle \left(\mathrm{CH}_{3}\right)_{3} \mathrm{~N}$ in aqueous solution?(ii)Write structural formulae of the compound A and B : \[\mathrm{CH}_{3} \mathrm{CONH}_{2} \xrightarrow{\mathrm{NaOBr}} \mathrm{~A} \xrightarrow[\text { Base }]{\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{COCl}} \mathrm{~B} \]A compound 'X' with molecular formula $\displaystyle \mathrm{C}_{3} \mathrm{H}_{9} \mathrm{~N}$ reacts with Hinsberg reagent to give a product insoluble in alkali. Identify 'X'.How can you convert aniline to benzonitrile ?(c)Why is $\displaystyle -\mathrm{NH}_{2}$ group of aniline acetylated before carrying out nitration ?
The reaction of amines with mineral acids to form ammonium salts shows that these are basic in nature. Aliphatic amines are stronger bases than ammonia whereas aromatic amines are weaker bases than ammonia. Aliphatic and aromatic primary and secondary amines react with acid chlorides, anhydrides and esters by nucleophilic substitution reaction. The main problem encountered during electrophilic substitution reactions of aromatic amines is that of their high reactivity. Substitution tends to occur at ortho-and para-positions. Hinsberg reagent is used for the identification and distinction between primary, secondary and tertiary amines. Aryldiazonium salts, usually obtained from arylamines, undergo replacement of the diazonium group with a variety of nucleophiles to provide advantageous methods for producing aryl halides, cyanides, phenols and arenes. Answer the following questions :
(i)
Why $\displaystyle \mathrm{CH}_{3}-\mathrm{NH}_{2}$ is a stronger base than $\displaystyle \left(\mathrm{CH}_{3}\right)_{3} \mathrm{~N}$ in aqueous solution?
(ii)
Write structural formulae of the compound A and B : \[\mathrm{CH}_{3} \mathrm{CONH}_{2} \xrightarrow{\mathrm{NaOBr}} \mathrm{~A} \xrightarrow[\text { Base }]{\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{COCl}} \mathrm{~B} \]
A compound 'X' with molecular formula $\displaystyle \mathrm{C}_{3} \mathrm{H}_{9} \mathrm{~N}$ reacts with Hinsberg reagent to give a product insoluble in alkali. Identify 'X'.
How can you convert aniline to benzonitrile ?
(c)
Why is $\displaystyle -\mathrm{NH}_{2}$ group of aniline acetylated before carrying out nitration ?
Marking-scheme solution
(i)
Due to combined effect of the inductive effect, solvation effect and
steric hinderance of the alkyl group.
(ii)
A= CH3NH2
B= CH3−NHCOC6H5
CH3−CH2−NH−CH3 / N – Methylethanamine
(c)
The nitration reaction can be controlled and the p-nitro derivative can be
obtained as the major product / To prevent the formation of anilinium ion
which is meta directing.
AminesChemical Reactions of AminesApplycase_studymedium
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CBSE Class 12 Chemistry past-paper question from the 2026board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.