JEE Main · 2021 · Shift-IeasyDNF-068

Which of the following is Lindlar catalyst?

d & f-Block Elements · Class 12 · JEE Main Previous Year Question

Question

Which of the following is Lindlar catalyst?

Options
  1. a

    Zinc chloride and HCl

  2. b

    Cold dilute solution of KMnO4\text{KMnO}_4

  3. c

    Sodium and Liquid NH3\text{NH}_3

  4. d

    Partially deactivated palladised charcoal

Correct Answerd

Partially deactivated palladised charcoal

Detailed Solution

Lindlar Catalyst:

Lindlar catalyst is partially deactivated (poisoned) palladium on calcium carbonate (or barium sulphate), treated with lead acetate and quinoline.

Key features:

  • Pd deposited on CaCO3\text{CaCO}_3 or BaSO4\text{BaSO}_4
  • Deactivated with lead acetate (Pb(OAc)2\text{Pb(OAc)}_2) and quinoline
  • Used for partial hydrogenation of alkynes to cis-alkenes

R-CC-R’+H2Lindlarcis-alkene\text{R-C}\equiv\text{C-R'} + \text{H}_2 \xrightarrow{\text{Lindlar}} \text{cis-alkene}

Why "partially deactivated palladised charcoal"? The option describes the essential feature — Pd (palladium) on a support, deactivated to prevent over-reduction.

Other options:

  • ZnCl₂/HCl: Lucas reagent (for alcohol classification)
  • Cold dil. KMnO₄: Baeyer's reagent (for oxidation/unsaturation test)
  • Na/liq. NH₃: Birch reduction

Answer: Option (4)

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Which of the following is Lindlar catalyst? (JEE Main 2021) | Canvas Classes