Question

The compound which shows highest reactivity towards nucleophilic displacement reaction is

• A. $R_2C=CHR > R_2C = CH_2 > R_2C = CR_2$
• B. $R_2C = CR_2 > R_2C = CHR > R_2C = CH_2$
• C. $R_2C = CH_2 > R_2C = CR_2 > R_2C = CHR$
• D. $R_2C - CR_2 > R_2C = CH_2 > R_2C = CHR$

Answer 1

Answer: (D)

Option D is correct.

Answer 2

For nucleophilic aromatic substitution, the presence of strong –I/–M groups (like –NO₂) at the ortho or para positions to the leaving group (Cl) greatly enhances reactivity by stabilizing the intermediate σ‐complex.

• In structure (A): Cl is at position 2 with NO₂ groups at positions 1 (ortho) and 4 (meta).
• In structure (B) and (C): Cl is at position 1 with a single NO₂ at position 2 (ortho).
• In structure (D): Cl is at position 1 with NO₂ groups at positions 2 (ortho) and 4 (para).

Thus, (D) has both ortho and para –NO₂ groups relative to the leaving group, providing the best stabilization of the intermediate; hence, it shows the highest reactivity.