VALENCE-BOND STUDIES OF CONTACT NUCLEAR SPIN-SPIN COUPLING .3. PI-ELECTRON COUPLING IN AROMATIC AND CYCLIC UNSATURATED HYDROCARBONS

Theoretical calculations of π-electron contributions to contact proton spin-spin coupling constants in aromatic and cyclic unsaturated systems are performed by means of a previously developed formalism which uses the generalized product approximation with intergroup configuration interaction and valence-bond wave functions. Theoretical results for a number of aromatic and unsaturated cyclic fragments are compared with the experimental data, and their significance for coupling mechanisms are discussed. Agreement of theoretical results with experiment is best for small, long-range coupling constants. Theoretical values for all of the indene long-range coupling constants should be useful for the detailed spectral analysis. Comparisons of the calculated and experimental results for cycloheptatriene suggest that the unsaturated portion of the molecule is very nearly planar in the liquid phase. © 1969, American Chemical Society. All rights reserved.