Isotope Effects on Magnetic Resonance Parameters in Hydrogen Bonded Systems
Roderick E. Wasylishen1, Victor V. Terskikh2, Maria A. Matlinska1, Qichao Wu1, Guy M. Bernard1, Michelle Ha1 and Andreas Brinkmann3
1Dept. of Chemistry, University of Alberta, Edmonton, Alberta, T6G 2G2, Canada
2Dept. of Chemistry, University of Ottawa, Ottawa, Ontario, K1N 6N5, Canada
3Metrology, National Research Council Canada, 1200 Montreal Road, Ottawa, Ontario, K1A 0R6, Canada
An early classic review of isotope effects on molecular properties was that of A.D. Buckingham and W. Urland (Chem. Rev., 1975, 75, 113-117). Isotope effects on NMR parameters have been studied and reviewed by many researchers including C.J. Jameson, P.E. Hansen, and H-H. Limbach. Here we report 2H/1H isotope effects on 13C NMR isotropic magnetic shielding constants in several molecules containing O–H–O fragments. The advantages of performing such measurements on solid samples will be illustrated. We find that the two-bond isotope effects, i.e., 2∆C(2/1H) values, in the hydrogen-bonded systems are often an order of magnitude larger than those observed in hydrocarbons. While qualitative interpretation of the experimental results is generally straightforward, quantitative interpretations are much more challenging. Several specific examples illustrating the computational challenges will be presented.