CBSE 2025 · Region 2 · Set 1 · Q27 · 3 marks
Explain the following reactions and write chemical equation involved :(a)Wolff-Kishner reduction(b)Etard reaction(c)Cannizzaro reactionWrite the structures of A, B and C in the following sequence of reactions : $\displaystyle \mathbf{2} \times \mathbf{1} \frac{\mathbf{1}}{\mathbf{2}}=\mathbf{3}$(a)$\displaystyle \mathrm{CH}_{3} \mathrm{COOH} \xrightarrow{\mathrm{SOCl}_{2}} \mathrm{~A} \xrightarrow{\mathrm{H}_{2}, \mathrm{Pd}-\mathrm{BaSO}_{4}} \mathrm{~B} \xrightarrow{\mathrm{H}_{2} \mathrm{~N}-\mathrm{NH}_{2}} \mathrm{C}$(b)$\displaystyle \mathrm{CH}_{3} \mathrm{CN} \xrightarrow[\text { 2. } \mathrm{H}_{2} \mathrm{O}]{\text { 1.(DIBAL-H) }} \mathrm{A} \xrightarrow{\text { Dil. } \mathrm{NaOH}} \mathrm{B} \xrightarrow{\Delta} \mathrm{C}$
Explain the following reactions and write chemical equation involved :
(a)
Wolff-Kishner reduction
(b)
Etard reaction
(c)
Cannizzaro reaction
Write the structures of A, B and C in the following sequence of reactions : $\displaystyle \mathbf{2} \times \mathbf{1} \frac{\mathbf{1}}{\mathbf{2}}=\mathbf{3}$
(a)
$\displaystyle \mathrm{CH}_{3} \mathrm{COOH} \xrightarrow{\mathrm{SOCl}_{2}} \mathrm{~A} \xrightarrow{\mathrm{H}_{2}, \mathrm{Pd}-\mathrm{BaSO}_{4}} \mathrm{~B} \xrightarrow{\mathrm{H}_{2} \mathrm{~N}-\mathrm{NH}_{2}} \mathrm{C}$
(b)
$\displaystyle \mathrm{CH}_{3} \mathrm{CN} \xrightarrow[\text { 2. } \mathrm{H}_{2} \mathrm{O}]{\text { 1.(DIBAL-H) }} \mathrm{A} \xrightarrow{\text { Dil. } \mathrm{NaOH}} \mathrm{B} \xrightarrow{\Delta} \mathrm{C}$
Marking-scheme solution
(a)
The carbonyl group of aldehydes and ketones is reduced to CH2 group on treatment with
hydrazine followed by heating with sodium or potassium hydroxide in high boiling solvent such
as ethylene glycol
(b)
Chromyl chloride oxidises methyl group of toluene to a chromium complex, which on
hydrolysis gives corresponding benzaldehyde.
(c)
Aldehydes which do not have α-hydrogen atom, undergo self-oxidation and reduction
reaction on heating with concentrated alkali gives salt of carboxylic acid and alcohol
(a)
A = CH3COCl (b) CH3CHO (c) CH3CH=NNH2
(b)
A = CH3CHO (b) CH3CH(OH)CH2CHO (c) CH3CH=CHCHO
Aldehydes, Ketones and Carboxylic AcidsChemical Reactions of Aldehydes, Ketones and Carboxylic AcidsUnderstandshort_answermedium
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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.