Volumetric Properties of Binary Mixtures of 2,4,6-Trimethylpyridine with 1,2-Ethanediol, Methanol, and Water, and the Association Energies of the O-H•••N Bonded Complexes

2,4,6-Trimethylpyridine forms 1:1 complexes with methanol, 1,2-ethanediol, and water due to the O-H center dot center dot center dot N bonds. The association energy of the complexes was calculated using MP2 and DFT methods. The complexes with 1,2-ethanediol and water aggregate in the liquid phase as a result of the O-H center dot center dot center dot O bonds. In spite of the higher O-H center dot center dot center dot N bond energy, the aggregation of the ethanediolic complexes is less pronounced than that of the aqueous ones. That is probably caused by the weaker induction effect due to the C-C chain separating the hydroxyl groups in the diol molecule. Aggregation is impossible in the methanolic system, because of the lack of proton-donating functional groups. Differences in the hydrogen bond energy and in the ability to aggregate are manifested in the volumetric properties of the mixtures.