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Chemistry · 2026 · 3 marks
Haloalkanes and HaloarenesChemical Reactions of Haloalkanes and Haloarenes3 marksAnalyseshort answer
CBSE 2026 · Region 1 · Set 1 · Q28
Compound 'X' with molecular formula C_4 H_9 Br reacts with aqueous KOH to give an alcohol. The rate of this reaction depends only on the…
Compound 'X' with molecular formula $\displaystyle \mathrm{C}_{4} \mathrm{H}_{9} \mathrm{Br}$ reacts with aqueous KOH to give an alcohol. The rate of this reaction depends only on the concentration of the compound 'X'. When an optically active isomer 'Y' of the compound 'X' was treated with aqueous KOH solution, the rate of reaction was found to be dependent on concentration of compound 'Y' and aqueous KOH both.
(a)
Write down the structural formula of both 'X' and 'Y'.
(b)
Out of 'X' and 'Y', which one will undergo racemisation and why ?
(c)
Out of 'X' and 'Y', which one will form product with inversion of configuration and why ?
Marking-scheme solution
(a)
X =
Y =
(b)
X, because reaction is SN
$\displaystyle 1$/ due to formation of planar carbocation as
intermediate.
(c)
Y, Because reaction is SN
$\displaystyle 2$/due to rear side attack of nucleophile.
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CBSE Class 12 Chemistry past-paper question from the 2026 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.