CameraIcon
CameraIcon
SearchIcon
MyQuestionIcon
MyQuestionIcon
1
You visited us 1 times! Enjoying our articles? Unlock Full Access!
Question

Which of the following is Lindlar catalyst?


A

Zinc chloride and HCl

No worries! We‘ve got your back. Try BYJU‘S free classes today!
B

Partially deactivated palladised charcoal

Right on! Give the BNAT exam to get a 100% scholarship for BYJUS courses
C

Sodium and Liquid NH3

No worries! We‘ve got your back. Try BYJU‘S free classes today!
D

Cold dilute solution of KMnO4

No worries! We‘ve got your back. Try BYJU‘S free classes today!
Open in App
Solution

The correct option is B

Partially deactivated palladised charcoal


The explanation for correct option:

(b) Partially deactivated palladised charcoal

  1. Partially deactivated palladised charcoal is known as Lindlar’s catalyst.
  2. It is a heterogeneous catalyst.
  3. The catalyst is used for the hydrogenation of alkynes to cis-alkenes (i.e. without further reduction into alkanes).
  4. It is composed of palladium that is deposited on calcium carbonate (CaCO3) and then poisoned by suitable catalytic poisons, the most common of which being lead and sulfur.
  5. Composition: 5%Pd-CaCO3+Pb(OCOCH3)2+Quinoline
  6. Reaction:
    COOH-CC-COOH(g)+H2(g)LindlarCOOH-C=C-COOH(g)AlkyneCis-alkene

The explanation for incorrect option:

(a) Zinc chloride and HCl

  1. The solution of anhydrous Zinc chloride in concentrated HCl is called Lucas reagent.
  2. The solution is used to distinguish the alcohols into primary, secondary and tertiary.
  3. The reaction is a substitution in which the chloride replaces a hydroxyl group.
  4. The best results for this test are observed in tertiary alcohols, as they form the respective alkyl halides fastest due to higher stability of the intermediate tertiary carbocation.
  5. Reaction:
    ROH(aq)+HCl(aq)ZnCl2RCl(aq)+H2O(l)AlcoholAlkylhalide

(c) Sodium and Liquid NH3

  1. It is a strong reducing agent used to reduce alkynes to trans-alkenes.
  2. It is also used to reduce aromatic ring to simple alkene (Birch Reduction)
  3. Reaction: -CC-Na/NH3-C=C-+NaNH2alkynetrans-alkene

(d) Cold dilute solution of KMnO4

  1. It is called Bayer's reagent.
  2. It is a strong oxidising agent.
  3. It is used for detect the presence of unsaturation in the compound. if the unsaturation or double bond is present the voilet colour of KMnO4 disappears.
  4. Reaction:

-C=C-(g)+2KMnO4(aq)+H2O(l)-C(OH)-C(OH)-+MnO2(aq)+K2MnO4(aq)alkenePotassiumwater1,2-diolManganesepotassiumpermanganatedioxidemanganate(Violet)(Brown)

Therefore, Option (b) is correct, Partially deactivated palladised charcoal is Lindlar's catalyst.


flag
Suggest Corrections
thumbs-up
4
Join BYJU'S Learning Program
similar_icon
Related Videos
thumbnail
lock
Hybridization
CHEMISTRY
Watch in App
Join BYJU'S Learning Program
CrossIcon