Chapter 18: Q40P (page 908)

Show how each of the following compounds can be synthesized from benzene:
a. o-nitrophenol
b. p-nitroaniline
c. p-bromoanisole
d. anisole

Short Answer

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Step by step solution

Nucleophilic aromatic substitution

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

Synthesizing the given compounds from benzene

a. Benzene reacts with $B r_{2}$ and $F e B r_{3}$ to form bromobenzene. This reacts with $H N O_{3}$ 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 $F e B r_{3}$ to form bromobenzene. This reacts with $H N O_{3}$ 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" $F e B r_{3}$ to form bromobenzene. This reacts with localid="1668411690639" $H N O_{3}$ 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" $F e B r_{3}$ to form bromobenzene. This reacts with localid="1668411734592" $H N O_{3}$ 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.