INVESTIGATIONS UTILIZING THE O-18 ISOTOPE SHIFT IN C-13 NUCLEAR-MAGNETIC-RESONANCE SPECTROSCOPY - 3 - OBSERVATION OF A SOLVENT DEPENDENCE FOR TERT-BUTYL ALCOHOL

Solvent effects on the magnitude of the O-18 isotope shift in C-13 NMR for the carbon bonded to the hydroxyl group in tert-butyl alcohol wer e investigated using an array of deuterated solvents and a more accura te measurement of the isotope shift at natural abundance C-13. For the first time, a solvent effect on the magnitude of the isotope shift wa s detected which was smallest in pyridine, and increased in the follow ing order: pyridine < acetone/p-dioxane < nitromethane < benzene < wat er. These results indicate that assignments of carbon signals based on the magnitude of isotope shifts must take into account the possibilit y of a solvent effect. (C) 1998 Elsevier Science Ltd. All rights reser ved.