2,4,6-Trinitrophenol (picric acid) can be prepared in good yield by:

Step-by-step solution

Direct nitration of phenol with concentrated nitric acid gives a poor yield of 2,4,6-trinitrophenol (picric acid) due to extensive oxidation of the highly activated aromatic ring. To achieve a good yield, the ring must be deactivated prior to the final nitration step. This is commonly done by first synthesizing 2,4-dinitrophenol (often from the hydrolysis of 2,4-dinitrochlorobenzene). The nitration of 2,4-dinitrophenol proceeds smoothly to give picric acid in good yield because the presence of two strongly electron