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Th.D. Ferris, Th.C. Farrar
The Concentration and Temperature Dependence of the Deuterium Quadrupole Coupling Parameter and Rotational Correlation Time of Ethanol-Carbon Tetrachloride Binary Mixtures
Concentration and temperature dependent measurements of the hydroxyl proton chemical shift and deuterium longitudinal relaxation time of binary mixtures of ethanol and carbon tetrachloride were made over a 60 degree temperature range. Concentrations ranged from 1.02 mole percent to neat ethanol. Ab initio calculations performed on thirteen different ethanol clusters (both cyclic and linear) show a linear correlation (R2 = 0.99) between the deuterium quadrupole coupling parameter, χD, and the hydroxyl proton chemical shift, δH: χD (kHz) = 291.48 - 14.96 δH, where δH is the proton chemical shift in ppm relative to TMS. From this correlation and experimental values of the chemical shift, values of χD were obtained. The values for χD range from 204 kHz for the neat liquid at 238 K to 284 kHz for infinite dilution in CCl4at 300 K. The χD values along with the measured deuterium relaxation times were used to calculate the rotational correlation time, τc. The correlation times range from 70 ps (238 K, 12.4 mole percent ethanol) to 1.3 ps (300 K, 1.0 mole percent). These correlation times and bulk viscosity data were used to calculate the average volume of the different ethanol supramolecular clusters present in the mixture. The average volumes range from 40 Å3 (monomer) in very dilute solution to 325 Å3 (cyclic pentamer) for the neat liquid.
Zeitschrift für Physikalische Chemie, Oldenbourg Wissenschaftsverlag
Print ISSN: 0942-9352
Volume: 214, 12/2000
Pages: 1659