Question

What are the products formed when phenol and nitrobenzene are treated separately with a mixture of concentrated sulphuric acid and concentrated nitric acid?

Answer 1

A mixture of concentrated sulphuric acid and concentrated nitric acid introduces nitro group into benzene ring in an electrophilic aromatic substitution reaction.
When phenol is treated separately with a mixture of concentrated sulphuric acid and concentrated nitric acid, 2,4,6-trinitrophenol ( also known as picric acid) is acid is obtained. Hydroxyl group is activating and ortho, para directing.
When nitrobenzene is treated separately with a mixture of concentrated sulphuric acid and concentrated nitric acid, m-dinitrobenzene is acid is obtained. Nitro group is deactivating and meta directing.