Experimental and Theoretical study of substituent effects on 3J(C-H) coupling constants in 1-X-biciclo(1.1.1) pentanes

DELLA, E. W.; LOCHERT, I. J.; NELIDA MARIA PERUCHENA; AUCAR, G.; CONTRERAS, R. H.

JOURNAL OF PHYSICAL ORGANIC CHEMISTRY

JOHN WILEY & SONS LTD

Año: 1996 vol. 9 p. 168 - 178

0894-3230

 series of 23 bridgehead-substituted bicyclo[1.1.1]pentanes were synthesized and the 3J(C1-H) coupling constants determined from their proton-coupled 13C NMR spectra. It was found that the values of the couplings are strongly dependent upon the type of substituent present, with powerful effects exerted by the halogens in particular. The IPPP-CLOPPA-INDO theoretical approach, which was employed to provide a measure of the extent of through-bond versus through-space transmission of coupling information, was found to give 3J(C1-H) values in good agreement with experimental data. Empirical substituent parameter regressions were performed and found to be consistent with the CLOPPA description of the increase in both the through-bond and through-space contributions to the coupling. The substituent parameter regressional analyses also demonstrated that electronegativity effects play a predominant role in determining the magnitude of the couplings, particularly in those substrates in which the substituent is attached to the ring system by a second-row element.