Lesson eLearning

Outline the Gabriel synthesis for preparing (butylamine) from 1‑bromobutane. Include (i) the reaction of potassium phthalimide with 1‑bromobutane, (ii) the hydrolysis step using hydrazine hydrate, and (iii) write the overall balanced equation for the conversion of the phthalimide intermediate to butylamine. Also state the name of the key intermediate formed after the first step.

hard 5 marks Class 12 · Chemistry · Amines
Answer
Butylamine is obtained; key intermediate is N‑butylphthalimide

The correct answer is Butylamine is obtained; key intermediate is N‑butylphthalimide — The organic product after the first alkylation step is called N‑butylphthalimide, the key intermediate that protects the amine function until it is liberated by hydrazine.

Step-by-step solution

  1. Step (i) – Alkylation: , where Phth = phthalimide anion. This is an reaction because the carbon attached to Br is primary.
  2. Step (ii) – Hydrazinolysis: .
  3. Step (iii) – Acidic work‑up of the hydrazide: .
  4. Combine steps (i) and (ii) to write the overall balanced equation:
  5. .
  6. The organic product after the first alkylation step is called N‑butylphthalimide, the key intermediate that protects the amine function until it is liberated by hydrazine.
Common mistake: Assuming an pathway or omitting the hydrazine‑hydrolysis step

Concept tested: Gabriel synthesis of primary amines

Published · How this solution was prepared and checked

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