%0 Journal Article
%A Sedó, Josep
%A Ventosa, Nora
%A Molins, Ma Antònia
%A Pons, Miquel
%A Rovira, Concepció
%A Veciana, Jaume
%D 2001
%T Stereoisomerism of Molecular Multipropellers. 2. Dynamic
Stereochemistry of Bis- and Tris-Triaryl Systems
%U https://acs.figshare.com/articles/journal_contribution/Stereoisomerism_of_Molecular_Multipropellers_2_Dynamic_Stereochemistry_of_Bis-_and_Tris-Triaryl_Systems/3685578
%R 10.1021/jo000474g.s001
%2 https://ndownloader.figshare.com/files/5775936
%K Interconversion graphs
%K propeller interconversion
%K triaryl systems
%K NMR time scale
%K Molecular Multipropellers
%K basis
%K exchange pathways
%K multipropeller
%K molecule
%K threshold mechanism
%K 2. Dynamic Stereochemistry
%K NMR study
%K stereochemical analysis
%K activation energy
%X The dynamic stereochemistry of bis- and tris-triaryl systems, the most simple “molecular
multipropellers”, is discussed on the basis of an extension of a systematic stereochemical analysis
based on a symmetry-adapted symbolic notation developed specifically for these molecules. A suitable
theoretical basis for our study is provided by the classical hypotheses concerning the dynamics of
simple triaryl systems as formulated by Mislow and co-workers (J. Am. Chem. Soc. 1973, 95, 1535−1547), which, once applied to molecular multipropellers, show the existence of two modes of
rearrangement for each propeller. Interconversion graphs for all molecules under study, covering
a wide span of structural complexity, are presented. A complete NMR study of a two- and a three-propeller molecule indicates that all experimentally observable exchange pathways are indeed
predicted by theoretical analysis. Moreover, quantitative analysis of 2D-EXSY experiments affords
the activation energy of the subset of pathways that give rise to observable interconversions on
the NMR time scale. Assuming that two-ring flips are the threshold mechanism for individual
propeller interconversion, the experimental evidence indicates a preference for the flip of the central
ring and one of the outer rings over the flip of two outer rings.
%I ACS Publications