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Chemistry · 2025 · 3 marks
CBSE 2025 · Region 2 · Set 1 · Q26
(a) Define the following: 2 + 1 = 3 (i) Enantiomers (ii) Racemic mixture (b) Why is chlorobenzene resistant to nucleophilic substitution reaction?
(a)
Define the following : $\displaystyle \mathbf{2}+\mathbf{1}=\mathbf{3}$
(i)
Enantiomers
(ii)
Racemic mixture
(b)
Why is chlorobenzene resistant to nucleophilic substitution reaction ?
Marking-scheme solution
(a)(i)
The stereoisomers related to each other as non-superimposable mirror images.
(ii)
A mixture containing dextro and laevo enantiomers in equal proportions.
(b)
C—Cl bond acquires a partial double bond character due to resonance / the carbon atom of
benzene attached to halogen is sp2-hybridised / Explanation through resonating structures.
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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.