‹ PrevQuestion 158 / 158 · latest first
✓ Board-verified
Chemistry · 2022 · 5 marks
CBSE 2022 · Region 2 · Set 3 · Q12
Read the following passage and answer the questions that follow: Amines constitute an important class of organic compounds derived by replacing one…
Read the following passage and answer the questions that follow : Amines constitute an important class of organic compounds derived by replacing one or more hydrogen atoms of ammonia molecule by alkyl/aryl groups. Amines are usually formed from nitro compounds, halides, amides, etc. They exhibit hydrogen bonding which influences their physical properties. Alkyl amines are found to be stronger bases than ammonia. In aromatic amines, electron releasing and withdrawing groups, respectively increase and decrease their basic character. Reactions of amines are governed by availability of the unshared pair of electrons on nitrogen. Influence of the number of hydrogen atoms at nitrogen atom on the type of reactions and nature of products is responsible for identification and distinction between primary, secondary and tertiary amines. Reactivity of aromatic amines can be controlled by acylation process.
(i)
Why does aniline not give Friedel-Crafts reaction ? $\displaystyle 1$
(ii)
Arrange the following in the increasing order of their $\displaystyle \mathrm{pK}_{\mathrm{b}}$ values : $\displaystyle 1$ \[\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NH}_{2}, \mathrm{NH}_{3}, \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{NH}_{2},\left(\mathrm{CH}_{3}\right)_{3} \mathrm{~N} \]
(iii)
How can you distinguish between $\displaystyle \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{NH}_{2}$ and $\displaystyle \left(\mathrm{CH}_{3} \mathrm{CH}_{2}\right)_{2} \mathrm{NH}$ by Hinsberg test ? $\displaystyle 1$
(iv)
Write the structures of A and B in the following reactions :
(I)
$\displaystyle \xrightarrow{\mathrm{Sn+HCl}}$ A $\displaystyle \xrightarrow{\mathrm{Br}_2 \text{ water}}$ B
(II)
$\displaystyle \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CONH}_{2} \xrightarrow{\mathrm{Br}_{2} / \text { alc. } \mathrm{KOH}} \mathrm{A} \xrightarrow[\text { Pyridine }]{\mathrm{CH}_{3} \mathrm{COCl}} \mathrm{B}$
How will you convert the following :
(I)
Benzoic acid to aniline
(II)
Aniline to p-bromoaniline
Marking-scheme solution
(i) Aniline is a Lewis base and it reacts with \(\displaystyle \mathrm{AlCl}_{3}\) to form a salt / N of aniline acquires positive charge with \(\displaystyle \mathrm{AlCl}_{3}\) and hence is a deactivating group.
(ii) \[\left(\mathrm{CH}_{3}\right)_{3} \mathrm{~N}<\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{NH}_{2}<\mathrm{NH}_{3}<\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NH}_{2}
\] \(\displaystyle \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{NH}_{2}<\left(\mathrm{CH}_{3}\right)_{3} \mathrm{~N}<\mathrm{NH}_{3}<\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NH}_{2}\) (As no medium (aqueous /gaseous) or phase is given both answers to be considered).
(iii)
Add Hinsberg reagent (benzene sulphonyl chloride) to both the compounds. \(\displaystyle \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{NH}_{2}\) gives ppt. that is soluble in alkali while the ppt. formed by \(\displaystyle \left(\mathrm{CH}_{3} \mathrm{CH}_{2}\right)_{2} \mathrm{NH}\) is insoluble in alkali.
(a)
(I)(A)
(B)
(II)(A)
$\displaystyle \mathrm{CH_3CH_2NH_2}$
(B)
$\displaystyle \mathrm{CH_3CH_2NHCOCH_3}$
(I)
$\displaystyle \xrightarrow[\Delta]{\mathrm{NH_3}}$ $\displaystyle \xrightarrow{\mathrm{NaOBr}}$
(II)
$\displaystyle \xrightarrow{\mathrm{CH_3COCl/Py}}$ $\displaystyle \xrightarrow[\mathrm{FeBr_3}]{\mathrm{Br_2}}$ $\displaystyle \xrightarrow{\mathrm{H_2O}}$
More from Amines
- Assertion: Acetanilide ( -NHCOCH_3 ) is less basic than aniline. Reason (R): Acetylation of aniline results in decrease of electron density on…2024 · asked 2×
- Among the following, which is the strongest base?2023 · asked 2×
- Which of the following is least basic?2023
- Assertion: Aliphatic primary amines can be prepared by Gabriel phthalimide synthesis. Reason (R): Alkyl halides undergo nucleophilic substitution…2024
- How will you obtain the following from benzene diazonium chloride? Write chemical equations involved: 3 []2026
- A compound 'A' on reduction with iron scrap and hydrochloric acid gives compound 'B' with molecular formula C_6 H_7 N. Compound 'B' on reaction with…2022
- Assertion: Aniline is a stronger base than ammonia. Reason (R): The unshared electron pair on nitrogen atom in aniline becomes less available for…2024
- Identify the primary amine from the given options:2024
CBSE Class 12 Chemistry past-paper question from the 2022 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.