J. A m . Chem. SOC.1984, 106, 5634-5640
5634
isotope effect was first advocated by Robertson and co-workers about one a n d one-half decades ago,I5 and very recently has received support from theoretical calculations by van der Zwan and H y n e ~ . ~ ~
Experimental Section Materials. Aldrich spectrophotometric grade CH,CN [(H,O] = 0.01 M by Karl Fischer titration) was used without further purification in preparing solutions with high water concentrations ([L,O] > 1 M). For use in preparing solutions with lower water concentrations, 100-mL samples of this CH,CN were dried by two successive bulb-to-bulb distillations on a vacuum line from 12-g portions of freshly activated (>3 h at T > 300 OC and P < torr) 3-A molecular sieve. Karl Fischer titration of this dried CH3CN indicated [H20]
