INVESTIGADORES
VALLEJOS Margarita De Las Mercedes
congresos y reuniones científicas
Título:
Preferential formation of the different hydrogen bonds during the microhydration of cycloether
Autor/es:
VALLEJOS, MARGARITA; PERUCHENA, NÉLIDA M.
Lugar:
Rivera Maya
Reunión:
Congreso; XXXVII Congress of Theoretical Chemists of Latin Expression; 2011
Resumen:
Hydration is a universal phenomenon
in nature, many chemical and biological processes occur in aqueous media. In
the hydration of organic compounds which have polar groups, water molecules
interact with them through both hydrophilic and hydrophobic hydration. One of
the most important intermolecular interactions that occurs in this type of hydration
is the hydrogen bond (H-bond). In the present work we have explored the
microhydration of tetrahydrofuran (THF) and tetrahydropyran (THP) compounds
considering the complexes THF/(H2O)n and THP(H2O)n(with n = 1-4) in order to gain insight about which intermolecular
interactions, either cycloether-water or water-water, are dominant and what
type of hydrogen bonding patterns are involved in the most stable microhydrated
structures of n-size. Geometry optimizations for the microhydrated
complexes were carried out with various possible initial guess structures using
the density functional approach. The changes in the different properties due to
the increase of n were also discussed. In addition, an analysis based on
atom in molecule (AIM) theory has also been carried out to understand the
charge distribution and to pinpoint the atoms or regions that experiencing the
larger changes in electron population, and in energy, upon the microhydration.
For the most favorable microhydrated complexes, two different hydrogen bonding
patterns were found. In one of them, a chain of water molecules engaged by Ow-Hw···Ow
H-bonds is simultaneously bonded to both hydrophilic and hydrophobic portion of
the cycloether by Ow-Hw··O1 and C-H···Ow
H-bonds, respectively. In the other one, the water molecules are
self?associated forming a close-loop and one of them also forms a Ow-Hw···O1
H-bond. A linear correlation is obtained for the sum of electron density at the
bond critical points (rb) with the interaction energy (DE) and
with the solute?solvent interaction energy (DEs?w) of the
microhydrated complexes. In addition, a new way to estimate the energetic contribution
as well as the preferential formation of the cycloether-water and water-water H-bonds
based completely on charge density was found. Even more, it allows to
differentiate the contribution from cycloether-water interactions in both
hydrophilic and hydrophobic contributions, it is therefore a useful tool for
studying the hydration of large biomolecules. It was revealed that as n
raises, the water-water contribution also increases whereas the cycloether-water
contribution decreases but it is not negligible. During the microhydration the
changes in atomic properties occur on the whole system, particularly in the
water groups wherein it was identified that the remarkable stabilization of
their oxygen atoms is crucial for the stabilization of the complexes.