C-13,H-2 COUPLING-CONSTANTS AND H-2-INDUCED C-13 NMR ISOTOPE CHEMICAL-SHIFTS IN DEUTERIATED CYCLOHEXANES - APPLICATION FOR MEASUREMENTS OF CONFORMATIONAL EQUILIBRIUM ISOTOPE EFFECTSстатья
Информация о цитировании статьи получена из
Web of Science
Дата последнего поиска статьи во внешних источниках: 27 мая 2015 г.
Аннотация:C-13, H-2 coupling constants and H-2-induced C-13 isotope shifts have been measured-in [H-2(1)]-cyclohexane 1 and [1,1-H-2(2)]cyclohexane 2. We have observed differences in C-13, H-2 coupling constants in 1 and 2 and also between the C-13 isotope shifts in 1 and 2 for each deuterium substitution. The observed differences in coupling constants for C-1, C-2 and C-3 are sums of intrinsic and thermodynamic effects and the intrinsic contribution predominates for C-1 while the thermodynamic contribution predominates for C-3. The differences in the C-13 isotope shifts are almost completely due to the non-additivity effects. Thus only the vicinal isotope effects for C-13, H-2 or C-13, H coupling constants can be expected to be used for the estimates shifts of conformational equilibria in deuteriated cycloalkanes.