Question

Which of the following is an appropriate set of reactants for the preparation of $1-methoxy-4-nitrobenzene$ and why?

Answer 1

For the preparation of $1-methoxy-4-nitrobenzene$, set-2 is more appropriate because attack of phenoxide ion on methyl bromide is more favourable than attack of methoxide ion on aryl halide. It occurs because during the $S{N}_2$ attack, leaving group tendency of halogen in aryl halide is lower than that in alkyl halide because of double bond character in $C-Br$ bond of aryl halide due to resonance.

These reactions can be given as –

Set 1 Reaction


Here, In $1^{st}$ step addition of nucleophile occurs while in $2^{nd}$ step elimination of leaving group takes place.

Set 2 Reaction



Since, alkyl halides $\left(C{H}_{3}Br\right)$ are more reactive than aryl halides in nucleophilic substitution reactions, therefore set – 2 reactants are preferred.