Nitrophenols are compounds of the formula HOC6H5−x(NO2)x. The conjugate bases are called nitrophenolates. Nitrophenols are more acidic than
phenol itself.[1]
with the
formula HOC6H4NO2. Three
isomeric nitrophenols exist:
o-Nitrophenol (2-nitrophenol; OH and NO2 groups are neighboring, a yellow solid.
m-Nitrophenol (3-nitrophenol, CAS number: 554-84-7), a yellow solid (m.p. 97 °C) and precursor to the drug
mesalazine (5-aminosalicylic acid). It can be prepared by nitration of
aniline followed by replacement of the amino group via its
diazonium derivative.[2]
p-Nitrophenol, yellow solid is a precursor to the
rice herbicide fluorodifen, the pesticide
parathion, and the human analgesic
paracetamol (also known as acetaminophen).
The mononitrated phenols are often
hydrogenated to the corresponding
aminophenols that are also useful industrially.[1]
Di- and trinitrophenols
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.
Safety
Nitrophenols are poisonous. Occasionally, nitrophenols contaminate the soil near former explosives or fabric factories and military plants, and current research is aimed at remediation.[3]