Controlled Formation of the Acid−Pyridine Heterosynthon over the Acid−Acid Homosynthon in 2-Anilinonicotinic Acids

Four substituted 2-anilinonicotinic acids were synthesized, and their crystal structures were analyzed. It was found that by chemically introducing bulky functional groups to the aniline ring of the molecules, it is possible to dislodge the planar conformation due to steric repulsion. As a result, acid−pyridine heterosynthons, not acid−acid homosynthons, are formed in the crystals. The study is believed to offer a refreshing case of how a molecule’s conformation can affect intermolecular interactions and consequent crystal packing.