Aminophenyl

Aminophenyl refers to the arylamino substituent derived from phenyl with one amino group, having formula C6H4NH2. As a substituent, it is used in organic synthesis to assemble more complex molecules. The term covers three positional isomers depending on the location of the amino group relative to the point of attachment: o-aminophenyl (2-aminophenyl), m-aminophenyl (3-aminophenyl), and p-aminophenyl (4-aminophenyl). In many contexts, the prefix like 4-aminophenyl indicates a para relationship to another substituent on the same ring or the site of attachment.

Aminophenyl groups are strongly activating in electrophilic aromatic substitution due to the amino group's electron-donating nature; the amino group can be protonated under acidic conditions, reducing activation. The amino group can be converted into a diazonium salt, enabling azo coupling and other reactions that form azo dyes or other linkages.

Applications include serving as building blocks in dyes and pigments, pharmaceuticals, agrochemicals, and polymer precursors. Several commercial compounds incorporate the aminophenyl moiety, such as p-aminophenyl derivatives used in synthetic routes to analgesics and other medicines.

Synthesis typically involves reduction of a nitrobenzene to an aniline, or diazotization of an amine to form diazonium intermediates for subsequent coupling. Safety considerations reflect that aminophenyl compounds are often toxic and can be irritants; anilines require careful handling and appropriate disposal.