4-Nitrophenol

4-Nitrophenol

Names
IUPAC name 4-Nitrophenol
Other names p-Nitrophenol para-Nitrophenol 4-Hydroxynitrobenzene PNP
Identifiers
CAS Number	100-02-7
3D model (JSmol)	Interactive image
ChemSpider	955
ECHA InfoCard	100.002.556
PubChem CID	980
CompTox Dashboard (EPA)	DTXSID0021834
InChI InChI=1/C6H5NO3/c8-6-3-1-5(2-4-6)7(9)10/h1-4,8H Key: BTJIUGUIPKRLHP-UHFFFAOYAP
SMILES O=[N+]([O-])c1ccc(O)cc1
Properties
Chemical formula	C6H5NO3
Molar mass	139.110 g·mol−1
Appearance	Colorless or yellow pillars
Melting point	113–114 °C
Boiling point	279 °C (534 °F; 552 K)
Solubility in water	10 g/L (15 °C) 11.6 g/L (20 °C) 16 g/L (25 °C)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

4-Nitrophenol (also called p-nitrophenol or 4-hydroxynitrobenzene) is a phenolic compound that has a nitro group at the opposite position of hydroxy group on the benzene ring.

Properties

4-Nitrophenol shows two polymorphs in the crystalline state. The alpha-form is colorless pillars, unstable at room temperature, and stable toward sunlight. The beta-form is yellow pillars, stable at room temperature, and gradually turns red upon irradiation of sunlight. Usually 4-nitrophenol exists as a mixture of these two forms.

In solution, 4-nitrophenol has a dissociation constant (pKa) of 7.08 at 22 °C. Solution of 4-nitrophenol alone appears colorless or pale yellow, whereas its phenolic salts tend to develop a bright yellow color. This color-changing property makes this compound useful as a pH indicator.

Uses

4-Nitrophenol is an intermediate in the synthesis of paracetamol. It is reduced to 4-aminophenol, then acetylated with acetic anhydride.

4-Nitrophenol is used as the precursor for the preparation of phenetidine and acetophenetidine, indicators, and raw materials for fungicides. Bioaccumulation of this compound rarely occurs.

In peptide synthesis, carboxylate ester derivatives of 4-nitrophenol may serve as activated components for construction of amide moieties.

4-Nitrophenol is a product of the enzymatic cleavage of several substrates. Amounts of 4-nitrophenol produced by a particular enzyme in the presence of its corresponding substrate can be measured with a spectrophotometer at or around 400 nm and used as a proxy measurement for the amount of the enzyme in the sample.

Toxicity

4-Nitrophenol irritates eyes, skin, and respiratory tract; and may cause the inflammation of those parts. It has a delayed interaction with blood and forms methaemoglobin which is responsible for methemoglobinemia, potentially causing cyanosis, confusion, and unconsciousness. When ingested, it causes abdominal pain and vomiting. Prolonged contact with skin may cause allergic response. Genotoxicity and carcinogenicity of 4-nitrophenol are not known. LD50: mouse, p.o. 282 mg/kg; rat, p.o. 202 mg/kg.

See also

• Nitrophenols