JEE Main 2025 Apr 7 Shift 1, Chemistry Q1: Properties of Alkenes

JEE Main2025Apr 7, Shift 1Chemistry

Given below are two statements :

Statement I : Ozonolysis followed by treatment with Zn, H $_{2}$ O of cis-2-butene gives ethanal.

Statement II : The production obtained by ozonolysis followed by treatment with Zn, H $_{2}$ O of 3, 6-dimethyloct-4-ene has no chiral carbon atom.

In the light of the above statements, choose the correct answer from the options given below

A
Both Statement I and Statement II are true
B
Statement I is false but Statement II are true
C
Statement I is true but Statement II is false
D
Both Statement I and Statement II are false

Solution

Statement I analysis: Reductive ozonolysis (O $_{3}$ followed by Zn/H $_{2}$ O) cleaves a C=C double bond into two carbonyl fragments. For cis-2-butene, $CH_{3} CH = CHCH_{3}$ , the symmetric cleavage gives two molecules of ethanal (CH $_{3}$ CHO).

$∴$ Statement I is correct.

Statement II analysis: 3,6-Dimethyloct-4-ene has the structure CH $_{3}$ CH $_{2}$ CH(CH $_{3}$ )CH=CHCH(CH $_{3}$ )CH $_{2}$ CH $_{3}$ . Ozonolysis cleaves the C4–C5 bond and yields two molecules of 2-methylbutanal: CH $_{3}$ CH $_{2}$ CH(CH $_{3}$ )CHO.

The carbon bearing the methyl group in 2-methylbutanal is attached to four different groups (H, CH $_{3}$ , C $_{2}$ H $_{5}$ , CHO), making it a chiral centre.

$∴$ Statement II is incorrect because the product does contain a chiral carbon.

Conclusion: Statement I is true, Statement II is false $\Rightarrow$ Option (3).

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JEE Main 2025 Apr 7 Shift 1, Chemistry Q1: Properties of Alkenes

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