Compounds containing a pyrazole fragment in their structure are part of many medicines and have a wide range of bioactivity (for example, antimicrobial, anti-tuberculosis, etc.), and are also successfully used for the development of various synthetic anti-tumor agents. Interest in them is also caused by the presence of hydrogen bonds, which are the main motive for self-organization of molecules. A theoretical study of the nature of hydrogen bonds in various hydrogen-bound motifs in 3,5-dimethylpyrazole was performed using the DFT/B3LYP/6-31G(d,p) method. The results obtained indicate the possible existence of dimeric, trimeric, and tetrameric cyclic forms. Geometric and energy parameters of hydrogen bonds N-H...N are determined and the energies of donor-acceptor interaction in possible forms of self-organization of the molecules of the studied compound are calculated. It has been established that the hydrogen bond (H-bond) is the result of the interaction of a hybrid unshielded pair of a nitrogen atom of one molecule and a loosening natural orbital between the nitrogen atoms of one molecule and the hydrogen of another molecule (σ* N-H). The formation of the binding σ-orbital of the H-bond indicates the predominance of covalent interaction in the hydrogen bond. The study and analysis of the results showed that the formation of supramolecular systems of 3,5-dimethylpyrazole most likely structures are trimers and tetramers.
Investigation of the nature of hydrogen bonds in 3,5-dimethylpyrazole