- o-Nitrophenol (1-Hydroxy-2-nitrobenzene; OH and NO2 groups are neighboring; CAS number: 88-75-5)
- m-Nitrophenol (1-Hydroxy-3-nitrobenzene)
- p-Nitrophenol (1-Hydroxy-4-nitrobenzene, CAS number: 100-02-7).
The chemical formula for all isomers is C6H5NO3.
Ortho and para Nitrophenol develop in the mixture with nitrating of phenol. There are yellow crystalline solids with the melting points 46 °C (ortho isomer) and 114 °C (para isomer). p-Nitrophenol has a weakly phenol-like smell and is soluble in hot water, ethanol, ether and chloroform.
Nitrophenols are poisonous via inhalation, swallowing and contact with the skin.
They can irritate the eyes, cause blood poisoning, liver damage, nausea, headache and obstruction of the airways. In connection with alcohol the effect is strengthened. During contact with the skin they should be washed off immediately with much water.
Nitrophenols result in the chemical, pharmaceutical and armaments industry as intermediate products with the production of dyes, leathers, rubber, pesticides, fungicides, and ammunition. They have poisonous effect on the nervous system of organisms.
A large problem represents the distribution of Nitrophenols and related compounds in groundwater. Such contamination is found occasionally in former explosive or fabric factories and military plants.
A new development for the complete purification of Nitrophenols from groundwater is a catalyst, which consists of iron with a Tetra Amido Tetra-Amido-macrocycle ligand (Fe-TAML) and which oxidation of the poisons makes possible by hydrogen peroxide. No further poisonous substances result. The catalyst was developed in 2003 at Carnegie Mellon University.