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Nucleophilic aromatic substitution happens in two steps; one is nucleophilic addition followed by elimination. This reaction is termed ${\mathbf{S}}_{\mathbf{N}}\mathbf{Ar}$ reaction. The incoming nucleophile must be a stronger base than the substituent being replaced.

a. Benzene reacts with $B{r}_2$ and $FeB{r}_3$ to form bromobenzene. This reacts with $HN{O}_3$ and $H_{2}S{O}_4$ to form o-nitrobromobenzene. This further reacts with base and heat to form p- nitrophenol.

Synthesis of o-nitrophenol from benzen

b. Benzene reacts with $B{r}_2$and $FeB{r}_3$ to form bromobenzene. This reacts with $HN{O}_3$ and $H_{2}S{O}_4$ to form p-nitrobromobenzene. This reacts with ammonia and heat to form p- nitrobenzeneaminium. This reacts with a base to form p-nitroaniline.

Synthesis of p-nitroaniline from benzene

c. Benzene reacts with localid="1668411677126" $B{r}_2$ and localid="1668411684403" $FeB{r}_3$ to form bromobenzene. This reacts with localid="1668411690639" $HN{O}_3$and localid="1668411697298" $H_{2}S{O}_4$ to form p-nitrobromobenzene. This reacts with localid="1668411704509" $C{H}_{3}O$ and heat to form 1-methoxy-4-nitrobenzene.

This reacts with localid="1668411711325" $H_2$and Pd/C to form 4-methoxyaniline. This reacts with sodium nitrite, HCl at zero degrees Celsius to form 4-methoxybenzenediazonium chloride. This reacts with CuBr to form p-bromoanisole.

Synthesis of p-bromoanisole from benzene

d. Benzene reacts with localid="1668411719159" $B{r}_2$ and localid="1668411726618" $FeB{r}_3$ to form bromobenzene. This reacts with localid="1668411734592" $HN{O}_3$and localid="1668411743113" $H_{2}S{O}_4$ to form p-nitrobromobenzene. This reacts with localid="1668411750681" $C{H}_{3}O$and heat to form 1-methoxy-4-nitrobenzene.

This reacts with localid="1668411758209" $H_2$ and Pd/C to form 4-methoxyaniline. This reacts with sodium nitrite, HCl at zero degreesCelsius to form 4-methoxybenzenediazonium chloride. This reacts with localid="1668411765706" $H_{3}P{O}_2$ to form anisole.

Synthesis of anisole from benzene