Identify product $[\mathrm{A}],[\mathrm{B}]$ and $[\mathrm{C}]$ in the following reaction sequence :

(A) $[\mathrm{A}]: \mathrm{CH}_{3}-\mathrm{CH}=\mathrm{CH}_{2},[\mathrm{~B}]: \mathrm{CH}_{3} \mathrm{CHO}$, [C] : HCHO

(B) $[\mathrm{A}]: \mathrm{CH}_{2}=\mathrm{CH}_{2},[\mathrm{~B}]:$ (see structure) [C] : HCHO

(C) $[\mathrm{A}]: \mathrm{CH}_{3}-\mathrm{CH}=\mathrm{CH}_{2},[\mathrm{~B}]: \mathrm{CH}_{3} \mathrm{CHO}$, [C] : $\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{OH}$

(D) $[\mathrm{A}]: \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{3},[\mathrm{B}]: \mathrm{CH}_{3} \mathrm{CHO},[\mathrm{C}]: \mathrm{HCHO}$

JEE Main · 2025 · 28 Jan 2025 · Shift 2 · Hydrocarbons

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Identify product

[A], [B]

and

[C]

in the following reaction sequence :

(A) $[A] : CH_{3} - CH = CH_{2}, [B] : CH_{3} CHO$ , [C] : HCHO✓ Correct
(B) $[A] : CH_{2} = CH_{2}, [B] :$ (see structure) [C] : HCHO
(C) $[A] : CH_{3} - CH = CH_{2}, [B] : CH_{3} CHO$ , [C] : $CH_{3} CH_{2} OH$
(D) $[A] : CH_{3} CH_{2} CH_{3}, [B] : CH_{3} CHO, [C] : HCHO$

Answer: (A)

Solution

Propyne,

C H_{3} - C \equiv C H

, undergoes controlled hydrogenation over Pd/C with

H_{2}

that stops at the alkene stage, giving propene,

C H_{3} - C H = C H_{2}

, as [A]. Ozonolysis of this alkene with a reductive (Zn,

H_{2} O

) work-up cleaves the double bond: the terminal

= C H_{2}

carbon is released as formaldehyde and the internal carbon as acetaldehyde. So [B] is

C H_{3} C H O

and [C] is

H C H O

JEE Main · 2025 · 28 Jan 2025 · Shift 2 · Single correct option

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JEE Main · 2025 · 28 Jan 2025 · Shift 2 · Hydrocarbons

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