Q16-69E - Organic Chemistry (Mcmurry)

Question

p-Bromotoluene reacts with potassium amide to give a mixture of m and p-methylaniline. Explain.

Step-by-Step Solution

Answer

The reaction followed as:

Step 1: Benzyne formation

When the elimination reaction occur in the substituted aromatic rings the unreactive and the unstable intermediate is formed called benzyne which is attacked by nucleophiles and followed by protonation to form the desired product.

Step 2: Reaction of p-Bromotoluene with potassium amide

When p- bromo toluene which is a substituted benzene react with potassium amide in which hydrogen is protonated by amide followed by Br ion removal benzyne formation takes place as an intermediate and then again ammonia is added to the triple bond of benzyne and the formation of two methylaniline observed.

Step 3: Mechanism

Mechanism followed as:

1. Abstraction of the proton with the elimination of Br ion 
2. Formation of benzyne intermediate
3. Addition of ammonia to benzyne
4. Formation of two methylaniline occur

Formation of methylaniline