CORRELATION OF C-13-H-1 COUPLING-CONSTANTS WITH ELECTRONIC-STRUCTURE IN BI-CYCLOALKANE AND POLYCYCLOALKANE - A PM3 AND HF 6-31G-ASTERISK ANALYSIS/

Muller-Pritchard-type ((1)J(13C-1H) = a x % s(C)) and related expressi ons are explored for the prediction, from standard quantum chemical mo dels, of one-bond C-H spin-spin coupling constants, in a series of bi- and polycyclics. Correlations of experimental (1)J(13C-1H) with quant ities computed from NBO analyses of PM3 and HF/6-31G wave functions// geometries are critically examined for 38 aliphatic hydrocarbons (61 d istinct tertiary C-H sites; J range >100 Hz). Experimental vs calculat ed coupling constants are best fit when the model includes contributio ns from atomic charges (q(H) and q(C)) along with s character at carbo n (% s(C)). Previously used geometrical measures of hybridization are also discussed. The relationships obtained can be employed to easily p redict one-bond C-H coupling constants at tertiary sites in polycyclic saturated hydrocarbons with experimentally useful accuracy. By using common computational chemistry methods for a large data set, we offer both a predictive tool for the practicing chemist and insights into th e validity of hybridization-based interpretations of coupling.