CBSE 2026 · Region 1 · Set 1 · Q31 · 5 marks
(a)An organic compound (X) has the molecular formula $\displaystyle \mathrm{C}_{5} \mathrm{H}_{10} \mathrm{O}$. Draw structures for (X) if it : $\displaystyle 3$ + $\displaystyle 2$(I)does not give Tollen's test but gives a positive iodoform test.(II)does not give Tollen's test and iodoform test but undergoes Aldol condensation.(III)undergoes Cannizzaro's reaction.(ii)Show how each of the following compounds can be converted to benzoic acid :(I)Acetophenone(II)Ethyl benzeneAnswer the following questions :(i)Draw structure of the $\displaystyle 2$, $\displaystyle 4$-dinitrophenyl hyzdrazone derivative of benzaldehyde.(ii)Arrange the following in increasing order of their reactivity towards HCN : Di-tert. butyl ketone, Acetaldehyde, Acetone(iii)Give a simple chemical test to distinguish between benzoic acid and ethyl benzoate.(iv)Write the name of the reagent to convert Ethanenitrile to Ethanal.(v)Draw the structure of 'X' in the following reaction : 
(a)
An organic compound (X) has the molecular formula $\displaystyle \mathrm{C}_{5} \mathrm{H}_{10} \mathrm{O}$. Draw structures for (X) if it : $\displaystyle 3$ + $\displaystyle 2$
(I)
does not give Tollen's test but gives a positive iodoform test.
(II)
does not give Tollen's test and iodoform test but undergoes Aldol condensation.
(III)
undergoes Cannizzaro's reaction.
(ii)
Show how each of the following compounds can be converted to benzoic acid :
(I)
Acetophenone
(II)
Ethyl benzene
Answer the following questions :
(i)
Draw structure of the $\displaystyle 2$, $\displaystyle 4$-dinitrophenyl hyzdrazone derivative of benzaldehyde.
(ii)
Arrange the following in increasing order of their reactivity towards HCN : Di-tert. butyl ketone, Acetaldehyde, Acetone
(iii)
Give a simple chemical test to distinguish between benzoic acid and ethyl benzoate.
(iv)
Write the name of the reagent to convert Ethanenitrile to Ethanal.
(v)
Draw the structure of 'X' in the following reaction :
Marking-scheme solution
(a)
.
(i)
(I)
(II)
(III)
(ii)
(I)
(II)
$\displaystyle 31$(b).
(i)
(ii)
Di-tert-butyl ketone < Acetone < Acetaldehyde
(iii)
Add NaHCO3 to both, benzoic acid will give a brisk effervescence while
ethyl benzoate will not.
(iv)
(i)
DIBAL−H (ii) H3O+ / (i) SnCl2+HCl (ii)H3O+
Aldehydes, Ketones and Carboxylic AcidsChemical Reactions of Aldehydes, Ketones and Carboxylic AcidsApplylong_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.