onitrophenol

Ortho-nitrophenol, commonly called o-nitrophenol, is the ortho isomer of nitrophenol, a class of compounds derived from phenol in which a nitro group is attached to the benzene ring adjacent to the hydroxyl group. The family includes ortho-, meta-, and para-nitrophenol; here the focus is on the ortho isomer. Its molecular formula is C6H5NO3. The molecule is typically a pale yellow solid and is only moderately soluble in water, with higher solubility in organic solvents.

Structure and properties are governed by the proximity of the nitro and hydroxyl groups. The ortho arrangement allows intramolecular interactions such as hydrogen bonding, which can influence acidity and spectral properties. Nitro substituents generally increase the acidity of the phenolic OH compared with phenol itself, with the exact pKa depending on the isomer and solvent.

Production and occurrence: o-Nitrophenol is typically produced by nitration of phenol in strongly acidic media, which yields a mixture of ortho and para nitrophenol isomers that are separated by crystallization or other purification steps. It can also arise as a degradation product or intermediate in the synthesis of other aryl compounds. It is encountered as a process chemical in industrial settings and can be released into the environment from manufacturing or agricultural sources.

Applications: It serves as an intermediate in the synthesis of dyes, pharmaceuticals, and agrochemicals. It can be converted to o-aminophenol, a common dye and polymer precursor, via reduction. In laboratory use, nitrophenols are also employed as UV-absorbers and, for the para isomer, as pH indicators; however, specific isomer behavior varies.

Safety: o-Nitrophenol is toxic and irritating to skin and eyes and can be harmful if inhaled or ingested. It should be handled with appropriate personal protective equipment and disposed of following regulatory guidelines.