2-nitrophenol
Nitrophenols consist of a phenol molecule with one or more nitro-groups attached to the aromatic ring. The term is most often used to describe singly nitrated phenols.
with the formula HOC6H4NO2. Three isomeric nitrophenols exist:
The mononitrated phenols are often hydrogenated to the corresponding aminophenols that are also useful industrially.
2,4-Dinitrophenol (m.p. 83 °C) is a moderately strong acid (pKa = 4.89). 2,4,6-trinitrophenol is better known as picric acid, which has a well-developed chemistry.
Nitrophenols are poisonous. Occasionally, nitrophenols contaminate the soil near former explosives or fabric factories and military plants, and current research is aimed at remediation.
...
Wikipedia