AIIMS 2019 Chemistry Nucleophilic Substitution Reactions MCQ Question
The Sₙ2 reaction is a single step reaction and given by less bulky groups. The ease of carbocation towards Sₙ2 reaction is shown below.
i > ii > iii
ii > i > iii
iii > ii > i
iii > i > ii
Correct Answer
Detailed Explanation
In an Sₙ2 reaction, the nucleophile attacks the electrophile in a single concerted step, favoring less sterically hindered substrates. Carbocation stability decreases with increasing steric hindrance, making option D (iii > i > ii) correct, as the least hindered substrate (iii) reacts more readily than the more hindered ones (i and ii). Options A, B, and C incorrectly rank the substrates based on steric hindrance, failing to recognize that greater steric bulk around the electrophilic carbon impedes the nucleophilic attack, thus slowing the reaction rate.
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