Application of the deuterium isotope effect on NMR chemical shift to studyproton transfer equilibrium

Proton transfer processes play a key role in many reactions of organic comp ounds and in many biochemical mechanisms. In particular, proton transfer in hydrogen bond complexes in solutions has attracted considerable attention. NMR spectroscopy is known to be a powerful tool in studying hydrogen bond and the proton transfer equilibrium. This review focuses on one specific ap plication of this method, based isotope effect are shortly reviewed. The ma in subject of discussion is a relationship between the primary (p)DeltaA(D) on measurement of the deuterium isotope effect on chemical shifts. The fac tors affecting the magnitude of this and the secondary (n)Delta C-13(D),(n) Delta N-15(D), (n)Delta O-17(D) deuterium isotope effects and the hydrogen bond strength and symmetry, proton dynamic and position of the proton trans fer equilibrium. The possibility of using the deuterium isotope effect to s tudy proton transfer equilibrium is suggested and illustrated with represen tative examples of tautomeric equilibrium in beta -diketones, beta -thioket ones, Schiff and Mannich bases, and proton transfer equilibrium in complexe s of organic and inorganic acids with pyridine. Some experimental details o f the method are given and its advantages are indicated.