Deuterium isotope effects, chemical shifts mole fraction

The deuterium isotope effects on chemical shift consists of intrinsic isotope effect (direct perturbation of the shielding of X atom) and equilibrium isotope effect (perturbation of the equilibrium caused by the isotopic substitution). The values of deuterium isotope effects are to some extent independent of chemical shifts and allow determination of the mole fraction of the forms in equilibrium. 

Deuterium isotope effects on 1SN chemical shifts Deuterium isotope effects on 15N chemical shifts AN(D), similarly as for AC(D), can be employed in determination of mole fraction of the proton transferred form Schiff bases.44 A similar correlation between the mole fraction of NFI-form and AN(D) values was found (Figure 2). For the Schiff bases in which proton transfer takes place, the AN(D) values varied from —2 to + 5 ppm and depend on solvent and temperature. The AN(D) values of... 

Figure 3.11 Observed deuterium isotope effects on C chemical shifts of fl-diketones as a function of the mole fraction. (Reproduced from Bordner et al. [21]. Copyright (1989), with permission of Wiley-VCH.)...

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