Question

Consider the following compounds : Chlorobenzene (I), 2,4,6-trinitrochlorobenzene (II), 2,4-dinitrochlorobenzene (III), 4-nitrochlorobenzene (IV). The correct order of increasing ease of nucleophilic substitution reactions of these compounds is :

• A. I < IV < III < II
• B. I < III < IV < II
• C. II < III < IV < I
• D. IV < III < II < I

Hint:

More o/p -NO2 groups stabilise the intermediate → faster NAS: 0 < 1 < 2 < 3 nitro groups.

Answer 1

The Correct Option is A

Rank by the count of ortho/para nitro groups, since each –NO₂ withdraws electron density and stabilises the intermediate formed when the nucleophile adds. Plain chlorobenzene has none and reacts the least; 4-nitro has one, 2,4-dinitro has two, and 2,4,6-trinitro (picryl chloride) has three and reacts the most.
So ease increases I < IV < III < II. Correct option: (A).