GIAO/DFT calculations of relative conformer energies and 1H NMR shifts of unsaturated alcohols in benzene

摘要: Density functional theory calculations were performed on alkenols and alkynols at the PBE1PBE/6-311 + G(d,p) level with inclusion of solvent (benzene) effects by integral-equation-formalism polarizable continuum model (IEFPCM). For smaller molecules, conformers in which OH group is vicinity double or triple bond are preferred, but this preference falls as alkyl chain lengthened. The effect relative Gibbs energies different irregular, only two cases, 3-buten-1-ol 3-butyn-1-ol, there marked levelling. Gauge-including atomic orbital calculations, based geometries using a larger basis set, cc-pVTZ, give nuclear magnetic resonance shifts for all protons each conformer. Overall calculated weighing these according to conformer population. Calculated values well correlated experimental data from high-dilution spectra same solvent, ranging about 0.4 5.8 ppm, slope 1.09 ± 0.01. Calculations some alcohols hetero-atom substituents confirm that also prefer gauche (synclinal) gas phase, less benzene. shifts, however, be average over 0.8 ppm higher than observed. Copyright © 2011 John Wiley & Sons, Ltd.