Question

Show how the following compounds can be prepared from the given starting materials. You can use any necessary organic or inorganic reagents.

a.

b.

Short answer

Toluene cannot be directly converted to N-methylbenzamide. So it undergoes several processes. First, toluene is heated with chromic acid to form benzoic acid. Chromic acid is a very good oxidizing agent which oxidizes methyl group into carboxylic acid.Now benzoic acid is converted to acid chloride by treating it with thionyl chloride. The product formed is benzoyl chloride. This benzoyl chloride can be directly converted to N-methylbenzamide by treating it with two molecules of methylamine. Thus the product is formed. The complete reaction is given below:

Synthesis of (a)

1. 
2. 

Step-by-step solution

Conversion of toluene to N-methylbenzamide (a)

Toluene cannot be directly converted to N-methylbenzamide. So it undergoes several processes. First, toluene is heated with chromic acid to form benzoic acid. Chromic acid is a very good oxidizing agent which oxidizes methyl group into carboxylic acid.Now benzoic acid is converted to acid chloride by treating it with thionyl chloride. The product formed is benzoyl chloride. This benzoyl chloride can be directly converted to N-methylbenzamide by treating it with two molecules of methylamine. Thus the product is formed. The complete reaction is given below:

Synthesis of (a)

Conversion of toluene to phenyl acetic acid

Toluene is brominated in the presence of sunlight to form bromomethyl benzene.This is treated with magnesium metal in ether medium to form a Grignard reagent, where is the phenyl group. The Grignard reagent is passed with carbon dioxide in acidic medium to form the final product, i.e. phenyl acetic acid. The complete reaction is given below:

Synthesis of (b)