Choose the correct set of reagents for the following conversion: {trans}({Ph-CH=CH-CH3}) {cis}({Ph-CH=CH-CH3})
Hydrocarbons · Class 11 · JEE Main Previous Year Question
Choose the correct set of reagents for the following conversion:
- a
, alc , ,
- b✓
, alc , , , Lindlar Catalyst
- c
, aq , , , Lindlar Catalyst
- d
, aq , ,
, alc , , , Lindlar Catalyst
Step 1: Understand the conversion required
Convert trans- (trans-1-phenylpropene) → cis- (cis-1-phenylpropene)
Direct interconversion of cis/trans isomers requires breaking the bond — not possible by simple rotation. Need a multi-step synthesis.
Step 2: Plan the synthetic route
Strategy: Convert the alkene → alkyne → back to cis-alkene
Answer: Option (b)
Key Points to Remember:
- Alc. KOH = -elimination; Aq. KOH = substitution
- Lindlar's catalyst → cis-alkene from alkyne
- (Birch) → trans-alkene from alkyne
- Trans alkene → alkyne → cis alkene via Lindlar's route
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