Correlation of the O–H⋯N bonds energy with the excess compression of binary mixtures of pyridine and its methyl derivatives with methanol and water

Experimental excess molar isentropic compressions for six binary systems: (pyridine, 2-methylpyridine or 2,6-dimethylpyridine) + (water or methanol) are correlated with the calculated theoretically association energies of the ROH⋯NA complexes that increase in the order: pyridine < 2-methylpyridine < 2,6-dimethylpyridine. In spite of stronger O–H⋯N bonds, the negative excesses for methanolic systems are smaller than for the aqueous ones. That is mainly because of the aggregation of water-amine complexes due to the O–H⋯O bonds. Differences in partial molar compressions of the amines in water and methanol solvents result most probably from the hydrophobic hydration in aqueous solutions.