Question

Order of reactivity towards nucleophilic substitution reaction of the compounds is

• A. i > ii > iii > iv
• B. ii > i > iii > iv
• C. iv > iii > ii > I
• D. iii > iv > ii > i

Answer 1

Answer: (C)

iv > iii > ii > I

Answer 2

Nucleophile attacks readily to the compound that has least electron density. Electron withdrawing groups like $- Cl , NO _{2}$ etc decrease the electron density while electron releasing groups like $NMe _{2}$ increase the electron density at benzene nucleus.
Compound (iv) due to the presence of four electron withdrawing groups has the least electron density and thus, is more reactive towards nucleophilic substitution.
Hence, the correct order of reactivity towards nucleophilic substitution is as