Phenol is nitrated much more easily than benzene. It reacts with dilute nitric acid at room temperature, with no need for concentrated sulfuric acid.Products
Mononitration gives a mixture of two isomers, 2-nitrophenol and 4-nitrophenol, and water:C6H5OH + HNO3 → C6H4(OH)NO2 + H2O The nitro group goes on at position 2 or 4 (numbering the carbon with the -OH group as 1). Position 6 is the same as position 2, so there are only two mononitrated isomers.Comparison with benzene
Benzene needs concentrated nitric acid and concentrated sulfuric acid at about 50 °C to form nitrobenzene; phenol reacts at room temperature with dilute acid. The difference is explained by the oxygen lone pair being partially delocalised into the ring, which increases its electron density and makes it more attractive to electrophiles.With concentrated nitric acid, phenol is nitrated three times, forming 2,4,6-trinitrophenol.Worked example: what is the maximum mass of nitrophenol that can form from 4.70 g of phenol (Mr 94.0)?
n(phenol) = 4.70 ÷ 94.0 = 0.0500 mol. Nitrophenol, C6H5NO3, has Mr = 72.0 + 5.0 + 14.0 + 48.0 = 139.0.mass = 0.0500 × 139.0 = 6.95 g This is the total for both isomers, which must then be separated.
Mononitration gives a mixture of two isomers, 2-nitrophenol and 4-nitrophenol, and water:
Benzene needs concentrated nitric acid and concentrated sulfuric acid at about 50 °C to form nitrobenzene; phenol reacts at room temperature with dilute acid. The difference is explained by the oxygen lone pair being partially delocalised into the ring, which increases its electron density and makes it more attractive to electrophiles.With concentrated nitric acid, phenol is nitrated three times, forming 2,4,6-trinitrophenol.Worked example: what is the maximum mass of nitrophenol that can form from 4.70 g of phenol (Mr 94.0)?
n(phenol) = 4.70 ÷ 94.0 = 0.0500 mol. Nitrophenol, C6H5NO3, has Mr = 72.0 + 5.0 + 14.0 + 48.0 = 139.0.