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JEE Main levelSingle correct optionDifficulty 2 of 3o1135

Imine formation between benzaldehyde and aniline becomes very slow at pH about 1 mainly because

  1. Abenzaldehyde is destroyed by acid
  2. Bmost of the aniline is protonated and is no longer nucleophilic
  3. Cthe carbinolamine cannot lose water in acid
  4. Dthe C=N bond is hydrolysed instantly

Answer: B

At low pH aniline exists as , which has no lone pair for attack on the carbonyl. The dehydration step itself is acid-catalysed and would be fast, so the first step becomes rate limiting and the overall rate falls.
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