Gibbs energy of cooperative hydrogen-bonding interactions in aqueous solutions of amines and pyridines

摘要

A method to determine the Gibbs energy of specific (hydrogen bonding) interactions of a solute with water isproposed. The energies of hydrogen bonding in bulk water are very difficult to determine by any method. The Gibbsenergy of hydration of substances forming hydrogen bonds with water is considered as the sum of contributions dueto non-specific interactions, the hydrophobic effect, and specific interactions. The first two terms were found to berather accurately described by empirical equations. The Gibbs energies of hydrogen bonding of aliphatic amines andpyridines in bulk water are determined, and the results are compared with the energies of their complexes with onemolecule of water. The cooperativity of hydrogen bonding is proved in aqueous solutions of amines and pyridines. Touse our equations, experimental values of the Gibbs energies of solvation in 'standard' solvents need to be known. TheGibbs energies of solvation of ten amines and pyridines in dimethyl sulfoxide are determined experimentally usingchromatographic head space analysis. The tendencies observed for the series of amines and pyridines are inagreement with other studies.