Dynamic behavior of hydrogen bonding in hydrogen 5,6-acenaphthenedicarboxylate

The dynamic hydrogen bond behavior of hydrogen 5,6-acenaphthenedicarboxylate has been studied using NMR spectroscopy at variable concentration and temperature. From the concentration experiments, it is clear that there is an equilibrium between monomeric (intramolecularly hydrogen bonded) and aggregated (intermolecularly hydrogen bonded) species at room temperature. Upon cooling, the equilibrium shifts completely toward intramolecular hydrogen bonding, thereby overcoming the steric cost required to form the necessary eight-membered ring. This compound is one of the few examples which exhibits such behavior, and the first within the series of hydrogen dicarboxylates where it has been observed by NMR spectroscopy.