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Chemistry · 2025 · 3 marks
CBSE 2025 · Region 1 · Set 1 · Q27
(a) Arrange the following compounds in increasing order of their boiling point: ( 1 + 2 = 3 ) ( CH_3)_2 NH, CH_3 CH_2 NH_2, CH_3 CH_2 OH. (b) Give…
(a)
Arrange the following compounds in increasing order of their boiling point: $\displaystyle (\mathbf{1}+\mathbf{2}=\mathbf{3})$ $\displaystyle \left(\mathrm{CH}_{3}\right)_{2} \mathrm{NH}, \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{NH}_{2}, \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{OH}$.
(b)
Give plausible explanation for each of the following :
(i)
Aromatic primary amines cannot be prepared by Gabriel Phthalimide synthesis.
(ii)
Amides are less basic than amines.
Marking-scheme solution
(a)
(CH₃)₂NH < CH₃CH2NH₂ < CH₃CH2OH
(b)(i)
aromatic halides do not undergo nucleophilic substitution with the anion formed by
phthalimide.
(ii)
/Due to resonance the lone pair on
nitrogen is less available for donation/ Due to +R effect lone pair of electrons is not easily
available on N of -NH2 group/ Due to -R effect of carbonyl group, electron density on N atom of -
NH2 group decreases.
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CBSE Class 12 Chemistry past-paper question from the 2025 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.