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Experimental and theoretical study of substituent effects on 3 J ( 13 C1‐ 1 H) coupling constants in 1‐X‐bicyclo[1.1.1]pentanes
Author(s) -
Della Ernest W.,
Lochert Ian J.,
Perucheélida M.,
Aucar Gustavo A.,
Contreras Rubén H.
Publication year - 1996
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/(sici)1099-1395(199603)9:3<168::aid-poc766>3.0.co;2-v
Subject(s) - substituent , chemistry , electronegativity , computational chemistry , coupling constant , bicyclic molecule , coupling (piping) , chemical shift , proton , stereochemistry , organic chemistry , quantum mechanics , physics , mechanical engineering , engineering
A series of 23 bridgehead‐substituted bicyclo[1.1.1]pentanes were synthesized and the 3 J (C1‐H) coupling constants determined from their proton‐coupled 13 C 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 3 J (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.