2nitrophenyl

2-Nitrophenyl refers to the aryl group derived from benzene with a nitro substituent at the ortho (2) position relative to the attachment point to the rest of the molecule. In practice, the term often denotes the o-nitrophenyl moiety used as a substituent in larger compounds, or as part of 2-nitrophenyl esters, ethers, or glycosides. The designation “2-nitrophenyl” is distinct from the meta- and para-nitrophenyl isomers (3- and 4-nitrophenyl).

Structure and properties: The nitro group is a strong electron-withdrawing substituent that deactivates the ring toward further electrophilic substitution and influences the reactivity of the attached moiety. The ortho relationship can affect steric interactions and the stability of derivatives, including the ease of formation of corresponding esters, carbonates, or glycosides. The 2-nitrophenyl group is commonly encountered as a leaving group in activated esters and as a chromogenic or assay substrate in biochemistry.

Preparation and use: 2-Nitrophenyl groups are typically introduced by electrophilic nitration of suitably substituted benzenes or by subsequent modification of preformed aryl scaffolds to install the nitro group at the ortho position. In practice, 2-nitrophenyl derivatives appear in synthetic reagents such as 2-nitrophenyl esters and carbonates used for acyl transfer and protection strategies, and in glycoside substrates. A well-known example is 2-nitrophenyl beta-D-galactopyranoside, used as a chromogenic substrate for beta-galactosidase assays, where release of 2-nitrophenol yields a yellow color.

Safety: Nitroaromatic compounds can be toxic and irritants; many are hazardous and should be handled with appropriate precautions in well-ventilated areas.