Structure and Acid-Base Properties of 1-Propylimidazole-4,5-dicarboxylic Acid

摘要

Abstract NMR spectra of 1-propylimidazole-4,5-dicarboxylic acid and its 1-alkyl C1-C4 derivatives in DMSO-d6 were studied. It was shown that these compounds are present in the zwitterion form in this solvent. The ionization constants of 1-propylimidazole-4,5-dicarboxylic acid in water were determined and their assignment was carried out, which is compatible with the assumption that this compound has a zwitterionic form in this solvent as well. Quantum chemical calculations confirmed both this assumption and the correctness of the assignment of deprotonation constants, and also allowed us to choose the preferred zwitter-ionic and monoanionic form of 1-propylimidazole-4,5-dicarboxylic acid from several alternative structures.