A NEW METHOD FOR THE DETERMINATION OF THE DYNAMIC ISOTOPE EFFECT AND THE DEUTERIUM QUADRUPOLE COUPLING-CONSTANT IN LIQUIDS

Using a self-consistent NMR method, it is now possible to determine bo th the deuterium quadrupole coupling constant as well as the rotationa l dynamic isotope effect in liquids. We successfully tested the method on benzene for temperatures between 280 K and 293 K, The average valu e of 185(3) kHz for the coupling constant is compared with measurement s in solid state and gas phase. As might be expected for liquids witho ut hydrogen bonds, no difference can be detected. A rotational dynamic isotope effect of 6(3)% is observed. This value is significantly smal ler than 20(5)%, the only other result reported in the literature. The results are corrected for the influence of vibrational motion. (C) 19 98 Academic Press.