Strong Coupling in Nuclear Resonance Spectra. IV. Exact Analysis of Three‐Spin Spectra

A method is developed for calculating the chemical shifts and spin‐spin coupling constants for a system of three spin‐½ nuclei (ABC) directly from the nuclear resonance spectrum. Trial‐and‐error adjustment of these parameters is avoided entirely, and the values obtained are exactly consistent with the input information. The use of experimental intensities is kept separate from that of experimental frequencies, and the former may be omitted entirely when experimental values of sufficient accuracy are not available. It is shown that previously unknown ambiguities in the assignment of parameters sometimes arise, and that conventional iterative analyses may occasionally lead to the wrong answer. The proton resonance spectra of four compounds containing vinyl groups are discussed as illustrations of the method.