JEE Main 2022 · 29 Jul · Shift 1 · Chemistry Q73

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ChemistrySingle correct+4 / -1Question 73 of 90

Which among the following pairs of the structures will give different products on ozonolysis ? (Consider the double bonds in the structures are rigid and not delocalized.)

The two Kekulé structures of m-xylene

Option A: the two Kekulé structures of 1,3-dimethylbenzene (m-xylene) joined by a resonance arrow.

The two Kekulé structures of p-xylene

Option B: the two Kekulé structures of 1,4-dimethylbenzene (p-xylene) joined by a resonance arrow.

The two Kekulé structures of o-xylene

Option C: the two Kekulé structures of 1,2-dimethylbenzene (o-xylene): one with the double bond between the two methyl-bearing carbons, one with a single bond there.

The two Kekulé structures of toluene

Option D: the two Kekulé structures of methylbenzene (toluene) joined by a resonance arrow.

Answer and worked solution

Official answer: C

Cleave each C=C and join the carbons left bonded by single bonds.

o-Xylene. With the C=C between the two methyl carbons: $\mathrm{CH_3COCOCH_3}$ + 2 OHC-CHO. With a single bond there: 2 $\mathrm{CH_3COCHO}$ + OHC-CHO. Different products.

The others. Both m-xylene forms give 2 $\mathrm{CH_3COCHO}$ + OHC-CHO; the p-xylene and toluene forms are identical by symmetry.

(C)

Topics:Aromatic hydrocarbons and electrophilic substitution Alkenes Resonance

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JEE Main 2022 · 29 Jul · Shift 1, Chemistry question 73