to , , -trinitrophenol. The product is commonly known as picric acid. The yield of the reaction product is poor. Nowadays picric acid is prepared by treating phenol first with concentrated sulphuric acid which converts it to phenol- , -disulphonic acid, and then with concentrated nitric acid to get , , -trinitrophenol.
Can you write the equations of the reactions involved? , , - Trinitrophenol is a strong acid due to the presence of three electron withdrawing –NO groups which facilitate the release of hydrogen ion. (ii) Halogenation: On treating phenol with bromine, different reaction products are formed under different experimental conditions. (a) When the reaction is carried out in solvents of low polarity such as CHCl or CS and at low temperature, monobromophenols are formed.
The usual halogenation of benzene takes place in the presence of a Lewis acid, such as FeBr (Unit , Class XII), which polarises the halogen molecule. In case of phenol, the polarisation of bromine molecule takes place even in the absence of Lewis acid. It is due to the highly activating effect of –OH group attached to the benzene ring. (b) When phenol is treated with bromine water, , , -tribromophenol is formed as white precipitate.
Write the structures of the major products expected from the following reactions: (a) Mononitration of -methylphenol (b) Dinitration of -methylphenol (c) Mononitration of phenyl methanoate. The combined influence of –OH and –CH groups determine the position of the incoming group.