Nitrobenzene can be prepared from benzene by using a mixture of conc. `HNO_3` and conc. In the nitrating mixture, `HNO_3` acts as a/an

Options

A. Base
B. Acid
C. Reducing agent
D. Catalyst

Answer

A

Explanation

In nitration, nitronium ion `overset(+)NO_2` is the nitrating agent. It is produced by the reaction of nitric acid and sulphuric acid
`HO - NO_2 + H_2SO_4 hArr overset(+)(H_2O) - NO_2 + HSO_4^(-)`
`overset(+)(H_2O) - NO_2 hArr H_2O + overset(+)(NO_2)`
`H_2O + H_2SO_4 hArr overset(+)(H_3O) + HSO_4^(-)`
On adding `HNO_3 + 2H_2SO_4 hArr NO_2^(+) + overset(+)(H_3O) + 2HSO_4^(-)`
Sulphuric acid acts as an acid and protonates nitric acid (which thus acts as a base) to form protonated nitric acid `(overset(+)H_2O - NO_2)`. The latter decomposes into nitronium ion.