CBSE 2026 · Region 2 · Set 1 · Q33 · 5 marks
An organic compound 'A', with molecular formula $\displaystyle \mathrm{C}_{2} \mathrm{H}_{6} \mathrm{O}$ reacts with active metals such as sodium to give compound 'B' and hydrogen gas. 'A on treatment with iodine and sodium hydroxide gives 'C' and in presence of $\displaystyle \mathrm{H}_{2} \mathrm{SO}_{4}$ at $\displaystyle 413$ K gives 'D' $\displaystyle \left(\mathrm{C}_{4} \mathrm{H}_{10} \mathrm{O}\right)$. 'D' on reaction with excess of HI gives 'E'. Identify 'A', 'B', 'C', 'D' and 'E' and write all the reactions involved.(B)Write the reagents which are used in the given conversions: $\displaystyle 3$ + $\displaystyle 2$(i)Phenol to $\displaystyle 2$, $\displaystyle 4$, $\displaystyle 6$ - tribromophenol(ii)Propene to propan-$\displaystyle 1$-ol(iii)Butan-$\displaystyle 2$-one to butan-$\displaystyle 2$-ol(b)Explain the mechanism of acid catalyzed hydration of alkene to form corresponding alcohol.
An organic compound 'A', with molecular formula $\displaystyle \mathrm{C}_{2} \mathrm{H}_{6} \mathrm{O}$ reacts with active metals such as sodium to give compound 'B' and hydrogen gas. 'A on treatment with iodine and sodium hydroxide gives 'C' and in presence of $\displaystyle \mathrm{H}_{2} \mathrm{SO}_{4}$ at $\displaystyle 413$ K gives 'D' $\displaystyle \left(\mathrm{C}_{4} \mathrm{H}_{10} \mathrm{O}\right)$. 'D' on reaction with excess of HI gives 'E'. Identify 'A', 'B', 'C', 'D' and 'E' and write all the reactions involved.
(B)
Write the reagents which are used in the given conversions: $\displaystyle 3$ + $\displaystyle 2$
(i)
Phenol to $\displaystyle 2$, $\displaystyle 4$, $\displaystyle 6$ - tribromophenol
(ii)
Propene to propan-$\displaystyle 1$-ol
(iii)
Butan-$\displaystyle 2$-one to butan-$\displaystyle 2$-ol
(b)
Explain the mechanism of acid catalyzed hydration of alkene to form corresponding alcohol.
Marking-scheme solution
(A)
.
OR
$\displaystyle 33$(B).(i)
Aqueous Br2
(ii)
HBr , Peroxide followed by hydrolysis / B2H6 , H2O2/OH−
(iii)
H2, Ni/Pd/Pt / LiAlH4
/ NaBH4
(b)
1. Protonation of alkene
2. Nucleophilic attack of water on carbocation
3. Deprotonation to form an alcohol
o O o -
Alcohols, Phenols and EthersAlcohols and PhenolsApplylong_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.