Thermodynamic stability of hydrogen-bonded systems in polar and nonpolar environments

Hasan Pašalić, Adélia J.A. Aquino, Daniel Tunega, Georg Haberhauer, Martin H. Gerzabek, Herbert C. Georg, Tatiane F. Moraes, Kaline Coutinho, Sylvio Canuto, Hans Lischka

Research output: Contribution to journalArticlepeer-review

25 Scopus citations

Abstract

The thermodynamic properties of a selected set of benchmark hydrogen-bonded systems (acetic acid dimer and the complexes of acetic acid with acetamide and methanol) was studied with the goal of obtaining detailed information on solvent effects on the hydrogen-bonded interactions using water, chloroform, and n-heptane as representatives for a wide range in the dielectric constant. Solvent effects were investigated using both explicit and implicit solvation models. For the explicit description of the solvent, molecular dynamics and Monte Carlo simulations in the isothermal-isobaric (NpT) ensemble combined with the free energy perturbation technique were performed, to determine solvation free energies. Within the implicit solvation approach, the polarizable continuum model and the conductor-like screening model were applied. Combination of gas phase results with the results obtained from the different solvation models through an appropriate thermodynamic cycle allows estimation of complexation free energies, enthalpies, and the respective entropic contributions in solution. Owing to the strong solvation effects of water the cyclic acetic acid dimer is not stable in aqueous solution. In less polar solvents the double hydrogen bond structure of the acetic acid dimer remains stable. This finding is in agreement with previous theoretical and experimental results. A similar trend as for the acetic acid dimer is also observed for the acetamide complex. The methanol complex was found to be tbermodynamically unstable in gas phase as well as in any of the three solvents.

Original languageEnglish
Pages (from-to)2046-2055
Number of pages10
JournalJournal of Computational Chemistry
Volume31
Issue number10
DOIs
StatePublished - Jul 30 2010

Keywords

  • Complexation in solution
  • Explicit and implicit solvation models
  • Hydrogen-bonded systems
  • Molecular dynamics and monte carlo simulations
  • Thermodynamic properties

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