Ar2NH

Ar2NH denotes a class of diarylamines, which are secondary amines in which two aryl groups are attached to nitrogen and one hydrogen remains on the nitrogen. The general formula is Ar2NH, where Ar represents an aryl group. The simplest member is diphenylamine (Ph2NH). Diarylamines occur as colorless to pale solids or liquids and are typically soluble in organic solvents but sparingly soluble in water. The nitrogen is usually pyramidal, and the aryl substituents can engage in conjugation with the nitrogen lone pair, reducing basicity relative to aliphatic amines and often more than in aniline.

Synthesis of Ar2NH compounds is commonly achieved by N-arylation, where an aryl electrophile is coupled with an amine source. Methods include Buchwald–Hartwig and Ullmann-type copper-catalyzed couplings to form symmetrical diarylamines such as diphenylamine, as well as unsymmetrical variants when two different aryl groups are used. Other routes include reduction of diaryl nitro compounds or nucleophilic substitution on activated arenes under appropriate conditions. These approaches enable introduction of a wide range of aryl groups onto nitrogen.

Applications of diarylamines span organic synthesis and materials science. They serve as intermediates in the preparation of dyes, pigments, and pharmaceuticals, and as building blocks for more complex amines. Diphenylamine, in particular, is widely used as an antioxidant and stabilizer in polymers, rubber, and related materials. Diarylamines also find use as ligands in coordination chemistry and as components in agrochemical or pharmaceutical research.

Safety and handling follow standard procedures for amines. Diarylamines can be irritants and may pose health hazards with improper exposure, so appropriate protective equipment and ventilation are advised.