Ágúst Kvaran*, Ásgeir E. Konrádsson,
Christopher Evansa) and Jón K.F. Geirsson
Science Institute, University of Iceland, Dunhaga 3, 107 Reykjavík,
Iceland.
a) Current Address: Department of Chemistry, Biology and Chemical Engineering, Ryerson Polytechnic University, 350 Victoria St., Toronto, ON, Canada, M5B-2K3
Abstract
1H NMR and UV-Vis spectroscopic studies as well as molecular
mechanics calculations have been performed for the trans and cis isomers
of a series of chlorine substituted stilbenes (2
- 10). Correlations are found between predicted molecular
conformations and various NMR and UV-Vis spectroscopic parameters, indicating
that these are suitable for conformational studies. The ethylene
proton chemical shifts, in particular, are found to be sensitive to anisotropy
effects of nearby C-Cl bonds. Both ethylene and some ring proton chemical
shifts are found to be dependent on ring current effects, which are substituent
and ring orientation dependent. UV spectra support the structural predictions
based on the molecular mechanic vs. NMR correlation analysis. Average minimum
energy conformations of compounds1
- 10 are given in the paper.