GATE 2021 CH – Question 43
Match the reaction in Group – 1 with the reaction type in Group – 2.
| Group – 1 | Group – 2 |
|---|---|
| P: Methylcyclohexane → Toluene + $3\mathrm H_2$ | I: Dehydrocyclization |
| Q: Ethylcyclopentane → Methylcyclohexane | II: Cracking |
| R: n-Octane → Ethylbenzene + $4\mathrm H_2$ | III: Dehydrogenation |
| S: n-Octane → n-Pentane + Propylene | IV: Isomerization |
The correct combination is:
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Correct answer: (B) P–III, Q–IV, R–I, S–II
Explanation
Check each chemical transformation.
- **P:** an existing cyclohexane ring loses hydrogen to become aromatic: **dehydrogenation (III)**.
- **Q:** the carbon skeleton rearranges without changing the molecular formula: **isomerization (IV)**.
- **R:** an open-chain alkane forms a ring and loses hydrogen: **dehydrocyclization (I)**.
- **S:** one larger hydrocarbon breaks into two smaller ones: **cracking (II)**.
The full match is **P–III, Q–IV, R–I, S–II**, option **B**.