Read the following passage and answer the next five questions based on it.
Aldehydes are generally more reactive than ketones in nucleophilic addition reactions due to steric and electronic reasons. Sterically, the presence of two large groups in ketones hinders the attack of nucleophile to carbonyl carbon than in aldehydes. Electronically, aldehydes are more reactive than ketones because two alkyl groups reduce the electrophilicity of the carbonyl carbon more effectively than in the former.
The order of reactivity of the given haloalkanes towards nucleophile is
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → RI > RBr > RCl
In a nucleophilic substitution, the C–X bond breaks and the halide ion leaves. The C–X bond becomes longer and weaker from Cl to I, because the larger halogen atom overlaps less with carbon, and the larger halide ion is also the better leaving group. So for the same alkyl group the reactivity towards nucleophiles is:
R–I > R–Br > R–Cl >> R–F
So R–I comes first, R–Br second and R–Cl last; this order holds for both SN1 and SN2 mechanisms.
Note: This question is from the chapter Haloalkanes and Haloarenes, while the passage is from the chapter Aldehydes, Ketones and Carboxylic Acids.
NCERT (2026-27 edition):
Reactions of Haloalkanes – …
