In this issue, Coxon (Bethesda, Maryland) provides a comprehensive survey of the many empirical variants of the Karplus-type equation that have been proposed over the years as NMR spectroscopy has evolved to become the indispensable key tool in carbohydrate characterization. The treatment covers spin couplings over three, four, and five bonds, and includes both protons and heteronuclei.
The equations range from simple, two-parameter versions that depict only the torsional dependence of coupling constants, to complex 22-parameter forms that simulate the variation of the coupling with many different molecular properties.