CBSE 2025 · Region 1 · Set 1 · Q33 · 5 marks

(a)

Carry out the following conversions : $\displaystyle (\mathbf{2}+\mathbf{3}=\mathbf{5})$

(i)

Ethanal to But-$\displaystyle 2$-enal

(ii)

Propanoic acid to ethane

(b)

An alkene A with molecular formula $\displaystyle \mathrm{C}_{5} \mathrm{H}_{10}$ on ozonolysis gives a mixture of two compounds B and C . Compound B gives positive Fehling test and also reacts with iodine and NaOH solution. Compound C does not give Fehling solution test but forms iodoform. Identify the compounds $\displaystyle \mathrm{A}, \mathrm{B}$ and C .

(b)

OR 33. (B) An organic compound (A) (molecular formula $\displaystyle \mathrm{C}_{8} \mathrm{H}_{16} \mathrm{O}_{2}$ ) was hydrolysed with dilute sulphuric acid to get a carboxylic acid (B) and an alcohol (C). Oxidation of (C) with chromic acid produced (B). (C) on dehydration gives But-l-ene. Identify (A), (B) and (C) and write chemical equations for the reactions involved.

CBSE Class 12 Chemistry past-paper question from the 2025board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.