A PROTON NMR-STUDY OF THE DEUTERIUM-PROTIUM FRACTIONATION IN AQUEOUS-SOLUTIONS OF SOME ORGANIC IONS

The dependence of the proton chemical shift of water on the concentration of sodium methane sulfonate, tetramethylammonium bromide, and tetrabutylammonium bromide was measured in water and in water-D//2O mixtures. Chemical shift data were used to calculate the fractionation factors ( phi ) for the methane sulfonate anion, the tetramethylammonium-, and the tetrabutylammonium cation. In agreement with the results of other studies the obtained fractionation factors (0. 97 plus or minus 0. 03, 1. 0 plus or minus 0. 05 for the above mentioned ions, respectively) indicate that the methane sulfonate anion decreases the structure of water (relative to that of bulk water) whereas the tetrabutylammonium cation is clearly a structure maker. The effect of the tetramethylammonium ion appears to be negligible.