CBSE 2023 · Region 1 · Set 3 · Q33 · 5 marks
(i)Carry out the following conversions:(1)Ethanal to But-$\displaystyle 2$-en-$\displaystyle 1$-al(2)Propanoic acid to $\displaystyle 2$-chloropropanoic acid(ii)An alkene 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'A', 'B'and'C'.(i)Distinguish with a suitable chemical test:(1)$\displaystyle \mathrm{CH}_{3} \mathrm{COCH}_{2} \mathrm{CH}_{3}$ and $\displaystyle \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CHO}$(2)Ethanal and Ethanoic acid(ii)Write the structure of oxime of acetone.(iii)Identify A to D. \(\displaystyle ```latex \text{CH}_3\text{COOH} \xrightarrow{\text{PCl}_5} \text{A} \xrightarrow{\text{H}_2/\text{Pd-BaSO}_4} \text{B} \xrightarrow{\begin{array}{l}\text{(i) CH}_3\text{/MgBr}\\\text{(ii) H}_3\text{O}^+\end{array}} \text{C} ``` and ```latex \text{B} \xrightarrow{\text{LiAlH}_4} \text{D} ```\)
(i)
Carry out the following conversions:
(1)
Ethanal to But-$\displaystyle 2$-en-$\displaystyle 1$-al
(2)
Propanoic acid to $\displaystyle 2$-chloropropanoic acid
(ii)
An alkene 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'A', 'B'and'C'.
(i)
Distinguish with a suitable chemical test:
(1)
$\displaystyle \mathrm{CH}_{3} \mathrm{COCH}_{2} \mathrm{CH}_{3}$ and $\displaystyle \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CHO}$
(2)
Ethanal and Ethanoic acid
(ii)
Write the structure of oxime of acetone.
(iii)
Identify A to D. \(\displaystyle ```latex \text{CH}_3\text{COOH} \xrightarrow{\text{PCl}_5} \text{A} \xrightarrow{\text{H}_2/\text{Pd-BaSO}_4} \text{B} \xrightarrow{\begin{array}{l}\text{(i) CH}_3\text{/MgBr}\\\text{(ii) H}_3\text{O}^+\end{array}} \text{C} ``` and ```latex \text{B} \xrightarrow{\text{LiAlH}_4} \text{D} ```\)
Marking-scheme solution
(i)
(1)
CH3CHO --dil. NaOH--> CH3CH(OH)—CH2—CHO --Δ, −H2O--> CH3—CH=CH—CHO
(2)
CH3CH2—COOH --(i) Cl2/Red P; (ii) H2O--> CH3—CH(Cl)—COOH
(ii)
A = CH3—CH=C(CH3)—CH3 / $\displaystyle 2$-Methylbut-$\displaystyle 2$-ene
B = H3C—CHO / Ethanal / Acetaldehyde
C = O=C(CH3)—CH3 / Propanone / Acetone
(i)
(1)
Add Iodine (I2), NaOH, and heat both the test tubes containing the given organic compounds. Butanone gives yellow precipitate (CHI3) while butanal will not give the positive iodoform test.
(2)
Add NaHCO3 in both the test tube containing the given organic compounds. Ethanoic acid will give brisk effervescence of CO2 and ethanal will not.
(ii)
(iii)
A = CH3COCl, B = CH3CHO, C = (CH3)2CH(OH), D = CH3CH2OH
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CBSE Class 12 Chemistry past-paper question from the 2023board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.