High-field 2Hmr spectrometry of deuteriated 1,3,3-trimethylbicyclo[2.2.1]heptan-2-ones. Determination of geminal deuterium isotope effects on deuterium chemical shift

By a high-field 2Hmr study of deuteriated 1,3,3-trimethylbicyclo[2.2.1]heptan-2-ones (fenchones), we have established that the geminal deuterium isotope effects on the exo-6-, endo-6-, and methyl deuterons are 1.46 ± 0.06 Hz (0.019 ppm), 1.61 ± 0.06 Hz (0.021 ppm), and 1.46 ± 0.06 Hz (0.019 ppm), respectively. From this study it is clear that high-field 2Hmr has the potential of providing directly all the information on the degree of deuterium substitution at carbon previously obtained indirectly by 13Cmr, while retaining the ability to identify chemically nonequivalent deuterons.