CBSE 2026 · Region 1 · Set 1 · Q28 · 3 marks
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 ?
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.
Haloalkanes and HaloarenesChemical Reactions of Haloalkanes and HaloarenesAnalyseshort_answerhard
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CBSE Class 12 Chemistry past-paper question from the 2026board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.