Thermodynamics of hydrogen bonding in hydrophilic and hydrophobic media
2006 (English)In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 110, no 9, 4393-4398 p.Article in journal (Refereed) Published
The thermodynamics of hydrogen bond breaking and formation was studied in solutions of alcohol (methanol, ethanol, 1-propanol) molecules. An extensive series of over 400 molecular dynamics simulations with an aggregate length of over 900 ns was analyzed using an analysis technique in which hydrogen bond (HB) breaking is interpreted as an Eyring process, for which the Gibbs energy of activation Delta G(not equal):can be determined from the HB lifetime. By performing simulations at different temperatures, we were able to determine the enthalpy of activation Delta H-not equal and the entropy of activation T Delta S-not equal for this process from the Van't Hoff relation. The equilibrium thermodynamics was determined separately, based on the number of donor hydrogens that are involved in hydrogen bonds. Results (Delta H) are compared to experimental data from Raman spectroscopy and found to be in good agreement for pure water and methanol. The Delta G as well as the Delta G(not equal) are smooth functions of the composition of the mixtures. The main result of the calculations is that Delta G is essentially independent of the environment (around 5 kJ/mol), suggesting that buried hydrogen bonds (e.g., in proteins) do not contribute significantly to protein stability. Enthalpically HB formation is a downhill process in all substances; however, for the alcohols there is an entropic barrier of 6-7 kJ/mol, at 298.15 K, which cannot be detected in pure water.
Place, publisher, year, edition, pages
2006. Vol. 110, no 9, 4393-4398 p.
IdentifiersURN: urn:nbn:se:kth:diva-77462DOI: 10.1021/jp0572535ISI: 000235944500080OAI: oai:DiVA.org:kth-77462DiVA: diva2:491646
QC 201202072012-02-072012-02-072016-04-20Bibliographically approved