CBSE 2025 · Region 2 · Set 1 · Q31 · 5 marks
(a)Give IUPAC name of $\displaystyle \mathrm{CH}_{3}-\mathrm{CH}=\mathrm{CH}-\mathrm{CHO}$. (b) Give a simple chemical test to distinguish between propanal and propanone. (c) How will you convert the following : (i) Toluene to benzoic acid (ii) Ethanol to propan-$\displaystyle 2$-ol (iii) Propanal to $\displaystyle 2$-hydroxy propanoic acid OR 31. (B) Complete each synthesis by giving missing starting material, reagent or products :(a) 
? (b) ? (i) $\displaystyle \mathrm{O}_{3}$ (ii) $\displaystyle \frac{\mathrm{O}_{3}}{\mathrm{Zn}-\mathrm{H}_{2} \mathrm{O}}$ $\displaystyle 2$ cyclohexanone $\displaystyle (=\mathrm{O})$ (c) 
(d) 
(e) 
(a)
Give IUPAC name of $\displaystyle \mathrm{CH}_{3}-\mathrm{CH}=\mathrm{CH}-\mathrm{CHO}$. (b) Give a simple chemical test to distinguish between propanal and propanone. (c) How will you convert the following : (i) Toluene to benzoic acid (ii) Ethanol to propan-$\displaystyle 2$-ol (iii) Propanal to $\displaystyle 2$-hydroxy propanoic acid OR 31. (B) Complete each synthesis by giving missing starting material, reagent or products :(a) ? (b) ? (i) $\displaystyle \mathrm{O}_{3}$ (ii) $\displaystyle \frac{\mathrm{O}_{3}}{\mathrm{Zn}-\mathrm{H}_{2} \mathrm{O}}$ $\displaystyle 2$ cyclohexanone $\displaystyle (=\mathrm{O})$ (c) (d) (e)
? (b) ? (i) $\displaystyle \mathrm{O}_{3}$ (ii) $\displaystyle \frac{\mathrm{O}_{3}}{\mathrm{Zn}-\mathrm{H}_{2} \mathrm{O}}$ $\displaystyle 2$ cyclohexanone $\displaystyle (=\mathrm{O})$ (c) (d) (e) Marking-scheme solution
(a)
But-$\displaystyle 2$-enal
(b)
On heating with NaOH + I2, propanone gives yellow ppt. Of iodoform (CHI3 ) whereas
propanal does not.
(i)
(ii)
(iii)(B)
(a)
(b)
(c)
(d)
(e)
CH3COCl / Anhy. AlCl3 or (CH3CO)2O/ Anhy. AlCl3
Aldehydes, Ketones and Carboxylic AcidsChemical Reactions of Aldehydes, Ketones and Carboxylic AcidsApplylong_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.