On the spin-spin coupling between13C and H separated by two bonds

Abstract

The model of Jameson and Gutowsky which has been successful in explaining systematic trends in coupling between directly bonded nuclei is applied to coupling constants across two bonds, in particular the CCH coupling. Empirical correlations of signs and magnitudes of CCH coupling with changing bonding situations for both carbons are explained on the basis of the model and the calculated values of γ for CCH, the nature of the transfer of spin information via the electrons in the sigma bonds between the coupled nuclei (which in these calculations is expressed as a function of a collection of resonance integrals) is examined, and the applicability of the results obtained here to the XCH coupling constant is discussed. The model and the calculations are found to be successful in explaining the observed correlations in CCH couplings, and appear to hold promise of the possibility of an overall understanding of K _XYZ down and across the periodic table.