Effect of Homologation on the Polymorphism of Anthranilic Acids

A series of homologues (1–4) of fenamic acid have been synthesized by varying the length of the linker between the two aromatic rings, and their polymorphism has been investigated. Under the same crystallization conditions, each of the newly synthesized compounds leads to two forms, except for compound 1, which indicates that additional flexibility due to homologation does not necessarily lead to more polymorphs. The molecules in each polymorphic system show different conformations due to the rotation about specific sigma bonds. Phase transitions are observed between the polymorphs of each system. Conformational analysis and Hirshfeld surface analysis were applied to investigate the effect of conformational flexibility on the polymorphism of these compounds.