Question

Consider the above compounds and choose the correct option(s) regarding nucleophilic aromatic substitution?

• A. (I) is more reactive than (II)
• B. (III) is less reactive than (II)
• C. $C-X$ bond does not break in the rate determinig step
• D. $C-X$ bond is broken in the rate determinig step

Answer 1

Answer: (A), (B), (C)

The correct options are
A (I) is more reactive than (II)
B (III) is less reactive than (II)
C $C-X$ bond does not break in the rate determinig step

(a) More electrongative $F$ atom increases the electrophilicity of the carbon to which it is attached hence 1-fluoro-4-nitrobenzene is more reactive.

(b) Reactivity will be more when $-N{O}_2$ is attached at ortho and para position to the leaving group and activates the ring towards nucleophilic substitution..

(c) In RDS, attack of nucleophile happens and $C-X$ bond breaks in fast step.