Nitrophenols are compounds of the formula HOC
6H
5−x(NO
2)
x. The conjugate bases are called nitrophenolates. Nitrophenols are more acidic than
phenol itself.
Mono-nitrophenols
with the
chemical formula HOC
6H
4NO
2. Three
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.
-
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
hydrogenation to the corresponding
that are also useful industrially.
[
]
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.[ Fact sheet at atsdr.cdc.gov]
