benzophenones

Benzophenones refer to a family of organic compounds that share a diaryl ketone structure, specifically a carbonyl group attached to two phenyl rings (Ph-CO-Ph). The parent compound, benzophenone, is a white crystalline solid. The term also covers numerous substituted derivatives in which one or both phenyl rings bear functional groups such as hydroxyl, alkyl, or halogen substituents. These derivatives differ in chemical reactivity and physical properties but retain the characteristic diaryl ketone core.

Production and structure are closely linked to the chemistry of Friedel–Crafts acylation. The parent benzophenone is typically prepared industrially by acylating benzene with benzoyl chloride in the presence of a Lewis acid catalyst (for example aluminum chloride). Substituted benzophenones are prepared by similar routes or by subsequent functional group transformations on the parent scaffold. Benzophenones are generally nonpolar and are insoluble in water, with the parent compound melting around 49°C and exhibiting high boiling points, making them suitable for use in nonpolar media.

Uses of benzophenones are diverse. They absorb ultraviolet light and are used as UV stabilizers and filters in plastics, coatings, and cosmetics; for example, certain derivatives function as UV absorbers to protect materials from UV degradation. Benzophenone derivatives also serve as photoinitiators in polymer chemistry, where they generate radicals upon exposure to light to drive polymerization. In some applications, they act as fragrance carriers or intermediates in organic synthesis.

Safety and regulation vary by derivative. While benzophenone itself has relatively low acute toxicity, some benzophenone-based UV filters (notably certain substituted derivatives) have raised environmental and health concerns, leading to regulatory scrutiny and restrictions in some regions. Proper handling and adherence to applicable safety data sheets and regulatory guidance are advised when working with these compounds.