A Spectroscopic and Computational Investigation of the Conformational Structural Changes Induced by Hydrogen Bonding Networks in the Glycidol-Water Complex

Rotational spectra were recorded in natural abundance for the C-13 isotoporners of two conformers of glycidol. Moments of inertia from the C-13 isotoporners were used to calculate the substitution coordinates and C-C bond lengths of two glycidol monomer conformations. The structures of seven different conformational minima were found from A initio (MP2/6-311++G(d,p)) optimizations of glycidol-water. The rotational spectrum of glycidol-water wits recorded using microwave spectroscopy, and the rotational constants were determined to be A = 3902.331 (11) MHz, B = 2763.176 (3) MHz, and C = 1966.863 (3) MHz. Rotational spectra were also recorded for glycidol-(H2O)-O-18, glycidol-DbOH, and glycidol-d(O)-D2O. The rotational spectra were assigned to the lowest-energy A initio structure, and the structure was improved by fitting to the experimental moments of inertia. The best-fit structure shows evidence for structural changes in glycidol to accommodate formation of the intermolecular hydrogen bonding network: the O-C-C-O torsional angle in glycidol was found to increase from 40.8 degrees for the monomer to 49.9 degrees in the water complex.