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Spatial structure and NMR spectra of strained [2.2.2]cyclophanes

✍ Scribed by Helena Dodziuk; Maciej Ostrowski; Kenneth Ruud; Jarosław Jaźwiński; Henning Hopf; Wiktor Koźmiński

Publisher
John Wiley and Sons
Year
2009
Tongue
English
Weight
152 KB
Volume
47
Category
Article
ISSN
0749-1581

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✦ Synopsis

Abstract

The chemical shifts and coupling constants in the NMR spectra of the title compounds are influenced by their strain and the proximity of the aromatic rings. These parameters are studied by density functional theory (DFT) calculations for 1–4 and measured for 3 and 4. We find that, in spite of the strain, the calculations reproduce the experimental values satisfactorily. This finding is of special importance for novel hypothetical molecules like hexahydrosuperphane 5 for their future identification and in searches of hydrocarbons exhibiting unusual NMR parameters. Our results demonstrate the influence of strain on the parameters studied. Most proton and carbon chemical shifts for the molecules under study having nonplanar aromatic rings differ considerably from the corresponding values for the relatively unstrained trimethylbenzenes and ethylbenzene. In addition, the calculated values of the coupling constants through three bonds in most cases do not follow Karplus relation. Copyright © 2009 John Wiley & Sons, Ltd.

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