Structural isomerization of 2-anilinonicotinic acids to 4-anilinonicotinic acids leads to an increase of ΔpKa, thus leading to the formation of a carboxylate–pyridinium NH dimer in the solid state.

To study whether C2 symmetric oligoureas form secondary structures such as sheets and helices/turns to serve as peptidomimetics, conformations of oligoureas composed of 1,2‐diaminocyclohexane and 1,2‐diphenyl‐1,2‐diaminoethane were investigated using X‐ray diffraction, UV, CD and NMR spectroscopic methods. Alternating heterochiral diamines in these chains strongly favored helical conformations. The conformations of C2‐symmetric chains of homochiral diamines were more conditional, giving indications of conditional extended and helical structure.