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.

4-nitrophenol is a member of the class of 4-nitrophenols that is phenol in which the hydrogen that is para to the hydroxy group has been replaced by a nitro group. It has a role as a human xenobiotic metabolite and a mouse metabolite. It is a conjugate acid of a 4-nitrophenolate.

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

Nitrophenols include two chemicals, 2-nitrophenol and 4-nitrophenol, which are very similar to each other. They are manufactured chemicals that do not occur naturally in the environment.

Nitrophenols (also referred to as mononitrophenols) exist in three isomeric forms: 2-nitrophenol (or ortho- or o-), 3-nitrophenol (or meta- or m-), and 4-nitrophenol (or para- or p-).

The most common effects noted at lethal doses are clinical signs of respiratory distress and neurotoxicity. Figure 1-1 shows the health effects found in animals following inhalation exposure to 2- or 4-nitrophenol; no inhalation data are available for 3-nitrophenol.

Everyone is exposed to very low levels of the nitrophenols in air, water, and soil. Workers who make or process the chemicals may be exposed to higher levels of them. Animal studies suggest that 4-nitrophenol may cause a blood disorder.

Direct ocular instillation of 4-nitrophenol in rabbits results in severe irritation, inflammation, corneal opacity and neovascularization, and visible destruction of the iris. No ocular effects were found following oral exposure to 4-nitrophenol.

Nitrophenol isomers (also referred to as mononitrophenols) are primarily used as intermediates to produce dyes, pigments, pharmaceuticals, rubber chemicals, photographic chemicals, and pesticides, including fungicides and lumber preservatives. 2-Nitrophenol is used to manufacture pesticides, fungicides, and other agricultural chemicals.

2-nitrophenol is a member of the class of 2-nitrophenols that is phenol in which one of the hydrogens that is ortho to the hydroxy group has been replaced by a nitro group. It is a conjugate acid of a 2-nitrophenolate.