NMR studies of conformations and dynamic processes—II : [26]Bicyclophanes with ethylene bridges |
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| Authors: | Thomas Olsson David Tanner Bengt Thulin Olof Wennerstrōm |
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| Institution: | Department of Organic Chemistry, Chalmers University of Technology and University of Göteborg, S-412 96 Göteborg, Sweden |
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| Abstract: | The conformations and dynamic processes in two bicyclophanes have been analysed on the basis of temperature-dependent 1H NMR spectra. Both bicyclophanes are suggested to have a lowest-energy conformation of D3 symmetry in which the substituents at all ethylene bridges are gauche+ (or gauche?) oriented. The interconversion of the mirror image conformers of each bicyclophane equilibrates the two hydrogens in each methylene group, the barriers being ca 36 and 37 kJ mol?1, respectively, as determined by line-shape analysis. |
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