Question

which of the following is the rate determining step in the nitration of benzene?

1.protonation of nitric acid 2.loss of a water 3. formation of arenium ion 4.loss of a proton by the arenium ion .

Answer 1

Correct answer is 3.

The electrophilic nitronium ion (NO₃)⁺ reacts with the nucleophilic C=C of the benzene. This is the rate determining step as it destroys the aromaticity of the benzene.

Generally, Benzene or any aromatic compound are very stable due to delocalization of electrons over all the connected atom in the respective ring (say 6 Carbon atom in benzene) hence it is little difficult to break the aromaticity for nitronium ion which leads the slow down of reaction and always slowest steps in a reaction determines its rate.