Question

Write an equation showing how you could prepare 2-bromo-4-nitroanisole from anisole and any necessary organic or inorganic reagents. If an ortho, para mixture is formed in any step of your synthesis, assume that you can separate the two isomers.

Answer 1

Answer:

(1) Sulphonation, (2) Bromination and (3) Desulphonation

Explanation:

• In the first step, anisole is being treated with $H_{2}SO_{4}$ to produce 4-methoxybenzenesulphonic acid as a predominat product.
• In the second step, 4-methoxybenzenesulphonic acid is being treated with $Br_{2}/FeBr_{3}$ to produce 3-bromo-4-methoxybenzenesulphonic acid predominantly due to combined directing effect of -OMe and $-SO_{3}H$ group.
• In the third step, 3-bromo-4-methoxybenznesulphonic acid is being treated with $H_{3}O^{+}/heat$ for desulphonation and to produce 2-bromo-4-nitroanisole.
• Full reaction scheme has been shown below.