Modelling hydrogen bonds in NN-dimethylformamide

N, N-dimethylformamide (DMF) is a universal' solvent with the simplest amide structure. DMF has different interactions with many polymers and biomolecules. It is therefore necessary to study systematically the interactions in DMF itself first. In this study, both FT-IR and two molecular theoretical methods (MP2 and DFT/B3LYP) were used to study various hydrogen bonding interactions in DMF molecules based on its weak H-bonding donors CH/CH3 and strong H-bonding acceptor C=O. The possible H-bonding donors and acceptors in DMF molecules were first analysed followed by modelling the effect of different structural environments on vC=O bands in infrared spectra. Finally, H-bonding properties including distance, angles and the energy as well as the probability of H-bonding patterns were obtained. The results showed that there exist five possible different weak types of H-bonding dimers; among them, three dimers consist of a pair of weak H-bonds, whereas two other dimers have two pairs of H-bonds, leading to 14 (including eight different) H-bonds. Two types of dimers were dominant, whereas three others can be omitted.