Measurements of long-range homonuclear coupling constants

Coupling constants in proton systems provide access to useful structural information, Several methods have been proposed to measure these constants in high-resolution spectra, but many of them are not well suited when the coupling constants are comparable to the spectral linewidth. In such a case the measurement of the apparent splitting, obtained from conventional NMR or from two-dimensional correlation spectroscopy (COSY), fan cause a miscalculation of the true coupling constant value, In this work, data processing for extracting small coupling constants is described. Signals are obtained from spin-echo experiments and analysed in the time domain in such a way that couplings are apparently multiplied by n + 1, where n is positive. Small coupling constants in 4-methyl-1,3-dioxane were obtained by this method. (C) 1997 by John Wiley & Sons, Ltd.