Lesson eLearning

Which reagent combination is used in the Gabriel synthesis to obtain a primary amine from an alkyl halide?

easy MCQ 1 mark Class 12 · Chemistry · Amines
  1. Potassium phthalimide and potassium hydroxide
  2. Sodium cyanide and water
  3. Hydrogen gas over a nickel catalyst
  4. Alkyl lithium followed by aqueous NH₃
Answer
Potassium phthalimide and potassium hydroxide

The correct answer is Potassium phthalimide and potassium hydroxide — Hence the correct reagent pair is potassium phthalimide and potassium hydroxide.

Step-by-step solution

  1. Identify the reagents that generate the phthalimide anion, which is the key nucleophile in the Gabriel synthesis.
  2. Potassium phthalimide reacts with KOH to give the phthalimide anion; this anion displaces the halide in an SN2 reaction to give N‑alkylphthalimide.
  3. Subsequent hydrolysis (not required in the question) liberates the primary amine.
  4. Hence the correct reagent pair is potassium phthalimide and potassium hydroxide.
Common mistake: Confusing the Gabriel reagent with cyanide or hydrogenation reagents

Concept tested: Gabriel synthesis of primary amines

Published · How this solution was prepared and checked

← All Amines questions