An investigation into intramolecular hydrogen bonding: impact of basis set and electron correlation on the ab initio conformational analysis of 1,2-ethanediol and 1,2,3-propanetriol

An NMR investigation of the importance of intramolecular hydrogen bonding in determining the conformational equilibrium of ethylene glycol in solution

“…These preferences are often attributed to the electron-attracting power of fluorine and oxygen, but quantum calculations that essentially agree on the fraction of gauche to be expected for simple molecules have been interpreted in different ways. 7,8,15,16,56 It would seem that electron-attracting power is not the only, or even the most important, influence in the gauche effect, because the cyano groups of 1,4-butanedinitrile, which, by conventional comparison, are more electron attracting than either fluorine or oxygen, have, at most, a rather feeble gauche effect. 28 2-Fluoroethanol (2) provides an instructive example of operation of the gauche effect with a substance for which strong intramolecular hydrogen bonding is often evoked.…”

“…Most significantly for the discussion here is the degree to which the preferences should be interpreted as the result of strong intramolecular hydrogen bonding between hydroxyl groups, especially when the geometries of such hydrogen bonds would not seem to be very favorable. Some representative pro examples involve infrared and Raman, 1 microwave, 2 electron and neutron diffraction, 3,4 molecular dynamics 5,6 and quantum calculations, 7,8 whereas con examples include infrared and Raman, 9 -13 molecular dynamics 5,6,14 and quantum calculations. 15 -17 This is an area where NMR can be expected to provide important information.…”

Conformational Preferences of Glycerol in the Gas Phase and in Water

“…In order to understand the conformational preferences of glycerol in gas phase and water, considerable experimental [5][6][7][8][9][10][11][12] and theoretical [12][13][14][15][16][17][18][19] studies have been carried out. In the gas phase, the electron diffraction experiments indicated that the two conformations αα and αγ are major conformations of glycerol, 5 whereas the microwave spectroscopic studies † This paper is to commemorate Professor Kook Joe Shin's honourable retirement.…”

“…Most of the previous works [13][14][15][16][17] took only the relatively small numbers (i.e., 8-13) of feasible conformers into account in interpreting the conformational distributions obtained from the electron diffraction, 5 microwave measurement, 11 and infrared spectra. 16 Although Law et al identified the 84 local minima from the 576 starting structures generated by the combination of the possible torsion angles, they optimized the structures at the relatively lower HF/3-21G level of theory in the gas phase and no comparison was made with the observed results.…”

“…Several ab initio HF and MP2 calculations [13][14][15]18,19 and density functional B3LYP studies [16][17][18] have been carried out in order to investigate the conformational preferences of glycerol in the isolated state (i.e., gas phase) and/or in water using various basis sets. Most of the previous works [13][14][15][16][17] took only the relatively small numbers (i.e., 8-13) of feasible conformers into account in interpreting the conformational distributions obtained from the electron diffraction, 5 microwave measurement, 11 and infrared spectra.…”