The concentration dependence of the proton chemical shift and the deuterium quadrupole coupling parameter for binary solutions of ethanol

Concentration dependent experimental measurements of the ethanol hydroxyl proton chemical shift SH for binary solutions were carried out. The solvents used were carbon tetrachloride (CCl4), benzene, chloroform, acetonitrile, acetone and dimethylsulphoxide (DMSO). The chemical shift values range from 0.69 ppm (relative to TMS) for dilute ethanol (extrapolated to infinite dilution) in CCl4 to 5.34 ppm for neat liquid ethanol. Ab initio calculations of the ethanol-solvent hydrogen bond energies show a correlation with the values for the chemical shift. The hydrogen bond energies for ethanol-solvent dimers range from 0.63 kcal mol(-1) for ethanol-CCl4 to 9.34 kcal mol(-1) for ethanol-DMSO. Theoretical calculations show a linear correlation between the deuterium quadrupole coupling parameter chi(D) and the isotropic proton chemical shift delta(H): chi(D)(kHz) = 291.48 - 14.96 delta(H), where delta(H) is the proton chemical shift in ppm relative to TMS (R-2 = 0.99). Using the concentration dependent chemical shift data and this equation, chi(D) is observed to range from 280 kHz for very dilute concentrations in CCl4, where the primary species is ethanol monomer, to 210 kHz for the neat liquid that is comprised primarily of cyclic pentamers.