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Chemistry · 2025 · 3 marks
Haloalkanes and HaloarenesChemical Reactions of Haloalkanes and Haloarenes3 marksAnalyseshort answer
CBSE 2025 · Region 5 · Set 2 · Q25
(a) Among the following, which will have inversion of configuration on reaction with aqueous alkali and why? (i) 1-chloropropane OR (ii)…
(a)
Among the following, which will have inversion of configuration on reaction with aqueous alkali and why ?
(i)
$\displaystyle 1$-chloropropane OR (ii) $\displaystyle 2$-chloro-$\displaystyle 2$-methylpropane
(b)
Which of the following (A) or (B) will be the major product in the reaction given below ? Give a suitable reason for your answer. \[\begin{aligned} \mathrm{CH}_{3}-\mathrm{CH}_{2} & -\mathrm{CH}(\mathrm{Br})-\mathrm{CH}_{3}+\text { alc. } \mathrm{KOH} \longrightarrow \\ & \mathrm{CH}_{3}-\mathrm{CH}_{2}-\mathrm{CH}=\mathrm{CH}_{2}(\mathrm{~A})+\mathrm{CH}_{3}-\mathrm{CH}=\mathrm{CH}-\mathrm{CH}_{3}(\mathrm{~B}) \end{aligned} \]
Marking-scheme solution
(a)(i)
$\displaystyle 1$-Chloropropane
$\displaystyle 1$°(Primary) alkyl halide / less sterically hindered carbon
(b)(B)
/CH3CH=CHCH3, ,as it has greater number of alkyl groups attached to the doubly bonded
carbon atom./ the preferred product is that alkene which has greater number of alkyl groups
attached to the doubly bonded carbon atom / By Saytzeff rule
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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.