A novel organic reaction leading to new 2-N-substituted benzoic acid ion-pair. A combination of physicochemical and theoretical calculations approaches

The 2-aminobenzimidazole (ABZ)-2-N-propanoyl benzoic acid 1 which is an intermediate of synthesis of various heterocyclic compounds was synthesized. The structure of 1 was confirmed by FT-IR, NMR (1D and 2D) spectra and XRD. The molecular structure of compound 1 was characterized by single-crystal X-ray structure determination and theoretical calculations based on DFT, HF and MP2 methods. The NBO analysis was used mainly in order to study the influence of electronic delocalization on the mechanism. Experimental, DFT, HF and MP2/6-31G(d) optimized bond lengths, bond angles and hydrogen bonding for the structure are studied also. The structure analysis shows that the 3D-supramolecular architecture of 1 is stabilized by means six-(S6) intramolecular and eight-( R 2 2 (8)) membered intermolecular hydrogen bonds, together with extensive C—H…O and C—H…π interactions between the carboxylate anion and the 2-aminobenzimidazolium cation. Furthermore, parameters derived from density functional theory in a local sense, in particular the softness and Fukui function were used to interpret and predict the mechanism of the reaction.