Question

Show how to convert toluene to 3 -hydroxybenzoic acid using the same set of reactions as in Example \(23.12\) but changing the order in which two or more of the steps are carried out.

Short answer

Question: Describe the sequence of reactions needed to convert toluene to 3-hydroxybenzoic acid. Answer: To convert toluene to 3-hydroxybenzoic acid, the following sequence of reactions should be performed: 1. Nitration of toluene to produce 2-nitrotoluene. 2. Reduction of 2-nitrotoluene to ortho-toluidine. 3. Acylation of ortho-toluidine to form N-acetyl-o-toluidine. 4. Bromination of N-acetyl-o-toluidine to obtain 3-bromo-N-acetyl-o-toluidine. 5. Hydrolysis of 3-bromo-N-acetyl-o-toluidine to produce 3-hydroxybenzoic acid.

Step-by-step solution

Nitration of Toluene

First, we will perform the nitration of toluene using a mixture of concentrated nitric acid (HNO3) and concentrated sulfuric acid (H2SO4). This reaction will lead to the formation of 2-nitrotoluene as the major product, with the nitro group at the ortho position. Toluene + HNO3 + H2SO4 -> 2-Nitrotoluene

Reduction of 2-Nitrotoluene

In the second step, we will reduce the nitro group in 2-nitrotoluene to an amine group using a reducing agent like tin (Sn) and hydrochloric acid (HCl). This reaction will produce ortho-toluidine as the product. 2-Nitrotoluene + Sn + HCl -> ortho-Toluidine

Acylation of ortho-Toluidine

Next, we will perform acylation on ortho-toluidine by reacting it with acetyl chloride (CH3COCl) in the presence of pyridine as a base. This reaction will introduce an acetyl group to the amine, forming N-acetyl-o-toluidine. ortho-Toluidine + CH3COCl + Pyridine -> N-acetyl-o-toluidine

Bromination of N-acetyl-o-toluidine

In order to introduce the hydroxyl group, we need to brominate N-acetyl-o-toluidine first. This is done by reacting it with bromine (Br2) in the presence of an iron (III) bromide (FeBr3) catalyst. The major product from this reaction will be 3-bromo-N-acetyl-o-toluidine. N-acetyl-o-toluidine + Br2 + FeBr3 -> 3-Bromo-N-acetyl-o-toluidine

Hydrolysis of 3-Bromo-N-acetyl-o-toluidine

Finally, hydrolyze 3-bromo-N-acetyl-o-toluidine using a strong base such as sodium hydroxide (NaOH). This reaction will remove the acetyl group and replace the bromine with a hydroxyl group, resulting in the formation of 3-hydroxybenzoic acid. 3-Bromo-N-acetyl-o-toluidine + NaOH -> 3-Hydroxybenzoic acid Thus, changing the order of the steps followed in Example 23.12, we successfully converted toluene to 3-hydroxybenzoic acid.