Author : Rubén H. Contreras,Cláudio F. Tormena,Lucas C. Ducati

Publisher : Elsevier Inc. Chapters

Release : 2013-06-08

ISBN : 0128083026

Language : En, Es, Fr & De

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**Book Description : **

In this chapter, several nJXY SSCC trends involving the X and Y light atoms are discussed with considerable detail for different values of n, the number of formal bonds separating both coupling nuclei. First, couplings contributed mainly by the FC interaction are considered. Insight into their transmission mechanisms is obtained using at least one of the following three approaches: (a) the qualitative model described in ; (b) the FCCP-CMO approach, that is, studying Fermi contact coupling pathways in terms of canonical molecular orbitals; and (c) by using explicitly the known connection between the Fermi Hole and the FC term transmissions. Among others, the following interesting examples are mentioned, the “Perlin effect” for n=1 and X=C and Y=either C or H. The different signs known experimentally for analogous geminal couplings are discussed in terms of exchange interactions taking place in the region where both bonds overlap. For multicyclic compounds with n=4, the FC transmission between bridgehead carbon atoms is rationalized in terms of series of concatenated sequences of hyperconjugative interactions involving those bridgehead atoms. Although the main emphasis is put on the FC term for different SSCCs, some discussions include also “noncontact” terms, where the PSO and DSO terms are described in some detail. In some cases, they are discussed in terms of the qualitative model described in , and examples where the “geometric effect” can be envisaged on physical grounds are described. This is only a brief description of some of the many interesting examples discussed within this chapter.