The Friedel-Crafts reaction between an aliphatic dibasic anhydride and an aromatic group results in the formation of an aroyl fatty acid with the aroyl group situated at the last carbon atom of an aliphatic chain. Since the lowest know dibasic anhydride is succinic anhydride, the number of methylene groups between the carboxyl group and the carbonyl group cannot be less than two. Since the time of the original reaction, it has been extended to include substituted succinic and maleic anhydride, glutaric anhydride, and the polymeric anhydrides of higher dibasic acids. Such as adipic acid or sebacic acid. The basic and extended reactions are discussed in this chapter.