Conformational stability of the propylene oxide-water adduct: direct spectroscopic detection of O-H...O hydrogen bonded conformers.

摘要: The 1:1 molecular adduct of propylene oxide and water (PO-H(2)O) was studied using Fourier transform microwave spectroscopy high level ab initio methods. Two distinct structural conformers with the molecule acting as a proton donor were detected experimentally: one on same side methyl group respect to ether ring, i.e., syn-PO-H(2)O, other binding O-atom from opposite group, anti-PO-H(2)O. nonbonded hydrogen is entgegen ring in both conformers. Rotational spectra four isotopic species, namely PO-H(2)O, PO-DOH, PO-HOD, PO-D(2)O, recorded for two bond parameters: r(O(epoxy)...H), angle(ring-O(epoxy)...H), angle(O(epoxy)...H-O) are 1.908 A, 112 degrees, 177 degrees 1.885 104.3 161.7 anti-PO-H(2)O, respectively. experimental results suggest that syn-PO-H(2)O stronger monomer subunits more rigidly locked their positions than ethylene oxide-water adduct. stabilizing effect intermolecular discussed terms experimentally estimated energies, parameters, calculations.