title: On the extent of intramolecular hydrogen bonding in gas-phase and hydrated 1,2-ethanediol.
abstract: We investigate the quantum dynamical nature of hydrogen bonding in 1,2-ethanediol and monohydrated 1,2-ethanediol using different levels of ab initio theory. Global full-dimensional potential energy surfaces were constructed from PW91/cc-pVDZ, B3LYP/cc-pVDZ, and MP2/cc-pVDZ ab initio data for gas-phase and monohydrated 1,2-ethanediol, using a modified Shepard interpolation scheme. Zero-point energies and nuclear vibrational wave functions were calculated on these surfaces using the quantum diffusion Monte Carlo algorithm. The nature of intra- and intermolecular hydrogen bonding in these molecules was investigated by considering a ground-state nuclear vibrational wavefunction with reduced complete nuclear permutation and inversion (CNPI) symmetry. Separate wavefunction histograms were determined from the ground-state nuclear vibrational wavefunction by projection into bondlength coordinates. The O-H and O-O wavefunction histograms and vibrationally averaged distances were then used to probe the extent of intra- and intermolecular hydrogen bonding. From these data, we conclude that gas-phase ethanediol may possess a weak hydrogen bond, with a relatively short O-O distance but no detectable proton delocalization. Monohydrated ethanediol was found to exhibit no intramolecular hydrogen bonding but instead possessed two intermolecular hydrogen bonds, indicated by both shortening of the O-O distance and significant proton delocalization. The degree of proton delocalization and shortening of the vibrationally averaged O-O distance was found to be dependent on the ab initio method used to generate the potential energy surface (PES) data set.
authors.affiliation: School of Chemistry, University of Sydney, NSW, Australia 2006. m.jordan@chem.usyd.edu.au
authors.forename: Deborah L
authors.initials: DL
authors.lastname: Crittenden
authors.forename: Keiran C
authors.initials: KC
authors.lastname: Thompson
authors.forename: Meredith J T
authors.initials: MJ
authors.lastname: Jordan
mesh_terms: D003198:Computer Simulation / Q000706:statistics & numerical data; D019855:Ethylene Glycol / Q000737:chemistry*; D005740:Gases / Q000737:chemistry*; D006859:Hydrogen / Q000737:chemistry; D006860:Hydrogen Bonding; D008968:Molecular Conformation; D009010:Monte Carlo Method; D010100:Oxygen / Q000737:chemistry; D014732:Vibration; D014867:Water / Q000737:chemistry*
chemical_list: D005740:Gases; D014867:Water; D006859:Hydrogen; D019855:Ethylene Glycol; D010100:Oxygen