Question

For the nitration of methyl benzoate, nitronium ion was prepared in a separate flask by adding HNO3 and H2SO4 together. However, methyl benzoate was added to H2SO4. What is the purpose of adding methyl benzoate to H2SO4?

Answer 1

The nitration of methyl benzoate occurs by electrophilic attack of nitronium ion on the ring.

During this attck, there is a carbonyl group present on the benzene which withdraws the electrons and hence, the nitronium ions attack at the meta position.(carbonyl withdraws the electrons)

In order to increase the yield of pure meta- compound, we add the methyl benzoate to the H2SO4 solution and this increases the electron withdrawing effect of the carbonyl due to protonation( O is protonated and hence, the carbonyl gains a posititve charge which increases the electron withdrawing effect).