Experimental and DFT studies on the transmission mechanisms of analogous NMR JCH and JCC couplings in 1-X- and 1-X-3-methylbicyclo[1.1.1]-pentanes

Experimental and DFT studies on the transmission mechanisms of analogous NMR JCH and JCC couplings in 1-X- and 1-X-3-methylbicyclo[1.1.1]-pentanes

Copyright (c) 2007 John Wiley & Sons, Ltd.

Bibliographische Detailangaben
Veröffentlicht in:Magnetic resonance in chemistry : MRC. - 1985. - 45(2007), 7 vom: 01. Juli, Seite 572-7
1. Verfasser: Contreras, Rubén H (VerfasserIn)
Weitere Verfasser: Esteban, Angel L, Díez, Ernesto, Lochert, Ian J, Della, Ernest W, Tormena, Cláudio F
Format: Aufsatz
Sprache:English
Veröffentlicht: 2007
Zugriff auf das übergeordnete Werk:Magnetic resonance in chemistry : MRC
Schlagworte:Journal Article
Beschreibung
Zusammenfassung:Copyright (c) 2007 John Wiley & Sons, Ltd.
The main aim of this work is to compare the transmission mechanisms for the Fermi contact term of spin-spin couplings, SSCCs, in series 1-X-bicyclo[1.1.1]-pentane, (1), and 1-X-3-methylbicyclo[1.1.1]pentane, (2), and from that comparison to gain insight into some subtle aspects of the FC transmission. To this end, 18 members of the latter series were isotopically enriched in (13)C at the methyl position and the following couplings were measured; 1JC3CMe, 3JC1CMe and 4JCXCMe. These three types of SSCCs in (2) are compared, respectively, with 1JC3H3, 3JC1H3 and 4JCXH in (1); these latter values were taken from previous works. Since electron delocalization plays an important role in the transmission of the FC interaction, the natural bond orbital (NBO) method is employed to quantify electron delocalization interactions within selected members of series (1) and (2). It is found that 1JC3H3 SSCCs in (1) is more efficiently transmitted than 1JC3CMe SSCCs in (2). On the other hand, 3JC1H3 and 4JCXH SSCCs in (1) are notably less efficiently transmitted than 3JC1CMe and 4JCXCMe SSCCs in (2), although substituent effects on these two SSCCs show the opposite trends. These different efficiencies are rationalized in terms of different sigma-hyperconjugative interactions in both series of compounds
Beschreibung:Date Completed 19.09.2007
Date Revised 04.06.2007
published: Print
Citation Status PubMed-not-MEDLINE
ISSN:1097-458X