Fenofibric acid.

Unlike the related fenofibrate molecule [Henry, Zhang, Gao & Bruckner (2003). Acta Cryst. E59, o699-o700], fenofibric acid {systematic name: 2-[4-(4-chlorobenzoyl)phenoxy]-2-methylpropanoic acid}, C17H15ClO4, contains a carboxylic acid moiety instead of an ester moiety. This polar moiety plays an important role in the formation of a rare acid-to-ketone hydrogen-bond-type packing interaction. The lack of an isopropyl group in fenofibric acid aligns the carboxyl group on the same side as the ketone carbonyl group; this conformation may play an important role in discrimination between the acid and the fenofibrate molecule in molecular recognition.