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Energetics of Bond Shift in Monohalogen-Substituted Cyclooctatetraenes

✍ Scribed by Stuart W. Staley; Russell A. Grimm; Gregory S. Martin; Rachel A. Sablosky

Publisher
Elsevier Science
Year
1997
Tongue
French
Weight
995 KB
Volume
53
Category
Article
ISSN
0040-4020

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✦ Synopsis

The free energies of activation for bond shift in fluoro-, chloro-, bromo-ad iodocyclocxtatetraencin THF-d8weredeterminedby 13CNMR spectroscopyto lx 12.7, 15.0, 15.4 sad 16.1 kcal/mol, respectively, at 298 K. Anafysis of HF/6-31G*-op!imizedgeomcuies and natural atomicchargesfor the groundstate and ring inversion trarzsitionstate for cyclooctatctraene(COT) ml its monoftuoroand monochloroderivativesindicatczthat the bond shift transition state for COT-F is stabilized (relative to COT) by electrostatic interactions between the fluorine and the flanking hydrogens,whereasthose of the largeshalogensare destabilizedby steric interactionswith the vicinal CH groups. G 1997Elsevier ScienceLtd.

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