Experimental and theoretical study of substituent effects on 3J(13C1-1H) coupling constants in 1-X-bicyclo[1.1.1]pentanes

✍ Scribed by Ernest W. Della; Ian J. Lochert; Nélida M. Peruchena; Gustavo A. Aucar; Rubén H. Contreras

• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: English
• Weight: 942 KB
• Volume: 9
• Category: Article
• ISSN: 0894-3230
• DOI: 10.1002/(sici)1099-1395(199603)9:3<168::aid-poc766>3.0.co;2-v

✦ Synopsis

A series of 23 bridgehead-substituted bicyclo[l.l.l]pentanes were synthesized and the 3J(Cl-H) coupling constants determined from their proton-coupled I3C 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(Cl-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 secondrow element.