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NEET CHEMISTRYAldehydes, Ketones and Carboxylic AcidsMedium

Question

Nucleophilic addition reaction will be most favoured in:

A

CH₃CH₂CH₂COCH₃

B

(CH₃)₂C=O

C

CH₃CH₂CHO

D

CH₃CHO

Step-by-Step Solution

  1. Reactivity Principle: Aldehydes are generally more reactive than ketones in nucleophilic addition reactions due to steric and electronic reasons.
  2. Steric Effect: The presence of two alkyl groups in ketones hinders the approach of the nucleophile to the carbonyl carbon more than the single alkyl group in aldehydes. Therefore, aldehydes are more reactive than ketones.
  3. Electronic Effect: Alkyl groups are electron-releasing (+I effect). They reduce the electrophilicity (positive charge density) of the carbonyl carbon. Ketones have two electron-releasing alkyl groups, whereas aldehydes have only one. This makes the carbonyl carbon in aldehydes more electrophilic and susceptible to nucleophilic attack.
  4. Comparison of Options:
  • Option 1 (Ketone): Least reactive due to larger alkyl groups and ketone nature.
  • Option 2 (Acetone - Ketone): Less reactive than aldehydes.
  • Option 3 (Propanal - Aldehyde): Reactive, but has a larger ethyl group compared to acetaldehyde.
  • Option 4 (Acetaldehyde - Aldehyde): Most reactive among the given options because it has only one small methyl group, offering the least steric hindrance and the least +I effect reduction of electrophilicity.
  1. Conclusion: Acetaldehyde (CH3CHOCH_3CHO) is the most reactive towards nucleophilic addition among the choices.

Exam Context & Concepts Covered

This question aligns with the NEET CHEMISTRY syllabus, specifically targeting concepts from Aldehydes, Ketones and Carboxylic Acids. 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.

CHEMISTRYAldehydes, Ketones and Carboxylic Acidsnucleophilicadditionreactionfavoured

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