Modified Karplus equations and their stereochemical applications

The current status of research on the Karplus equation for the vicinal spin—spin coupling constants (SSCC)³ J _HH, of fundamental significance in applications of NMR spectroscopy for establishing the configuration and conformational features of organic compounds in solutions, is discussed in the review. The data on the analysis of the fundamental molecular factors that affect the³ J _HH SSCC were generalized: the dihedral angle between interacting protons, the electronegativities of - and -substituents, the H-C-C valence angles, the C-C bond length, and effects of "proximity of substituents." The stereochemical applications of different modifications of the Karplus equation proposed in recent years were examined and comparatively analyzed. Possible ways of improving the accuracy of predicting the³ J _HH SSCC by using modern modifications of the Karplus equation and the method of molecular mechanics were discussed.N. N. Semenov Institute of Chemical Physics, Russian Academy of Sciences, 117977 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 7, pp. 1483–1506, July, 1992.