Question

A mixture of 0.10 mol benzene and 0.10 mol p-xylene was allowed to react with 0.10 mol nitronium ion until all the nitronium ion was gone. Two products were obtained: 0.002 mol of one and 0.098 mol of the other.

1. What was the major product?
2. Why was more of one product obtained than of the other?

Short answer

a. Major product is shown below:

b. Para-xylene is more reactive than benzene towards electrophilic substitution. Ortho position is having more chance for methyl substitution.

Step-by-step solution

Synthesis of 1,4-dimethyl-2-nitrobenzene

The major product 1,4-dimethyl-2-nitrobenzene is obtained by reaction benzene with 1,4-xylene in the following way:

Synthesis of 1,4-dimethyl-2-nitrobenzene

Reason for major product

Para-xylene is more reactive than benzene towards electrophilic substitution. Ortho position is having more chance for methyl substitution.

Alkyl substituents are ortho-para directors because they attached directly to the positively charged carbon.