A hydrocarbon 'X' with formula C6H8 uses two moles of H2 on catalytic hydrogenation of its one mole. On ozonolysis, 'X'…
Hydrocarbons · Class 11 · JEE Main Previous Year Question
A hydrocarbon 'X' with formula uses two moles of on catalytic hydrogenation of its one mole. On ozonolysis, 'X' yields two moles of methane dicarbaldehyde (malonaldehyde). The hydrocarbon 'X' is:
- a
hexa-1,3,5-triene
- b
1-methylcyclopenta-1,4-diene
- c
cyclohexa-1,3-diene
- d✓
cyclohexa-1,4-diene
cyclohexa-1,4-diene
Step 1: Analyze the given information
- Formula: → DoU =
- Absorbs 2 mol → has 2 double bonds (accounts for 2 DoU)
- Remaining 1 DoU = 1 ring (cyclic compound)
- Ozonolysis gives 2 moles of malonaldehyde ()
Answer: Option (d) — cyclohexa-1,4-diene
Key Points to Remember:
- Ozonolysis of cyclic dienes opens the ring at both bonds
- Count carbons: ozonolysis products must sum to starting material carbons
- Malonaldehyde from cyclohexa-1,4-diene: positions 1,4 give symmetric cleavage
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