ArCOAr

ArCOAr is a general representation for diaryl ketones, a class of organic compounds in which a carbonyl group links two aryl rings. In this shorthand, Ar denotes an aryl group such as phenyl or substituted phenyl. The simplest member is benzophenone (Ph-CO-Ph). When the two aryl groups are different, the compound is an unsymmetrical diaryl ketone (Ar-CO-Ar′).

Structure and properties: The carbonyl carbon in diaryl ketones is connected to two aromatic rings, which can lead to conjugation and influence UV absorption, color, and reactivity. Diaryl ketones are typically colorless solids or liquids; bulky or electron-rich aryl groups can alter melting points and solubility. Benzophenone and many derivatives absorb UV light and are used as UV absorbers and photoinitiators in polymer chemistry.

Synthesis: The most common preparation is Friedel–Crafts acylation: arenes (Ar-H) react with aryl carbonyl chlorides (Ar′-CO-Cl) in the presence of a Lewis acid such as AlCl3 to yield diaryl ketones Ar-CO-Ar′. Unsymmetrical diaryl ketones may require selective acylation strategies or alternative routes, including catalyzed cross-coupling approaches using suitable acyl electrophiles.

Applications: Diaryl ketones, especially benzophenone and substituted relatives, are used as UV stabilizers and UV absorbers, as well as photoinitiators in UV-curing coatings and plastics. They also serve as intermediates in organic synthesis and appear in fragrance and material-science contexts.