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NEET CHEMISTRYHydrocarbonsMedium

Question

The most suitable reagent for the following conversion is-

A

Hg2+/H+,H2OHg^{2+}/H^+, H_2O

B

Na/liquid NH3Na/\text{liquid } NH_3

C

H2,Pd/C,quinolineH_2, Pd/C, \text{quinoline}

D

Zn/HClZn/HCl

Step-by-Step Solution

  1. Identify the Reagent: The reagent specified in Option 3 is dihydrogen gas (H2H_2) in the presence of palladium supported on charcoal (Pd/CPd/C) and deactivated with quinoline or sulphur. This specific combination is known as Lindlar’s catalyst [NCERT 11th, Ch 13, Sec 13.3.4; Source 125].
  2. Function: Lindlar's catalyst is used for the partial reduction of alkynes to cis-alkenes. The reaction involves the syn-addition of hydrogen. RC≡CR′+H2→Pd/C,quinolinecis-alkeneRC\equiv CR' + H_2 \xrightarrow{Pd/C, \text{quinoline}} \text{cis-alkene}
  3. Context (NEET 2019): In the original exam question, the reaction scheme (missing from the input text) depicted the conversion of but-2-yne to cis-but-2-ene.
  4. Analysis of Other Options:
  • Na/liquid NH3Na/\text{liquid } NH_3 (Birch reduction) reduces alkynes to trans-alkenes . Hg2+/H+,H2OHg^{2+}/H^+, H_2O is used for the hydration of alkynes to form ketones or aldehydes. Zn/HClZn/HCl is a reducing agent typically used for alkyl halides or Clemmensen reduction.

Exam Context & Concepts Covered

This question aligns with the NEET CHEMISTRY syllabus, specifically targeting concepts from Hydrocarbons. Mastering this topic is crucial for scoring well in the upcoming medical entrance examinations. Solving conceptually related problems will help you understand the nuances of these concepts and improve your problem-solving speed.

CHEMISTRYHydrocarbonssuitablereagentfollowingconversion

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Phenylacetylene undergoes a reaction with dilute $\text{H}_2\text{SO}_4$ in the presence of $\text{HgSO}_4$ to yield:

A.Option 1 (Structure missing)
B.Option 2 (Structure missing)
C.Option 3 (Structure missing)
D.Option 4 (Structure missing)
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A.(Option 1 Structure Missing)
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C.4
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A.(i) > (ii) > (iii) > (iv)
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X and Y in the above-mentioned reaction are respectively:

A.X = 2–Butyne; Y = 3–Hexyne
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Match the bond line structures of hydrocarbons given in List-I with the corresponding boiling points given in List-II. List-II (Boiling point in K): (i) 300.9 (ii) 282.5 (iii) 309.1 (iv) 341.9 Choose the correct answer from the options given below:

A.(a)-(i), (b)-(iv), (c)-(iii), (d)-(ii)
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A.$60^{\circ}$
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The correct statement regarding the comparison of staggered and eclipsed conformations of ethane is:

A.The eclipsed conformation of ethane is more stable than staggered conformation because eclipsed conformation has no torsional strain.
B.The eclipsed conformation of ethane is more stable than staggered conformation even though the eclipsed conformation has a torsional strain.
C.The staggered conformation of ethane is more stable than eclipsed conformation because staggered conformation has no torsional strain.
D.The staggered conformation of ethane is less stable than eclipsed conformation because staggered conformation has a torsional strain.
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