From:	<SCHMITZ "-at-" MARSHALL.EDU>
Date:	Mon, 28 Jul 1997 18:49:48 -0400 (EDT)
Subject:	barrelene

Douglas A. Smith wrote:

< I need some help, references, etc.

< I know a number of years ago Lou Allinger did some ab initio calculations
< on barrelene, i.e., bicyclo[2.2.2]actatriene.  I believe these were at the
< HF/6-31G* level and were published in the Journal of Computational
< Chemistry.
<
< (1)  Has anyone published more recent calculations, or using a higher level
< of theory and/or larger basis set?  What about methods including
< perturbation, correlation, CI, or DFT?
<
< (2)  Is barrelene aromatic or antiaromatic?  I recall the latter, but
< cannot prove it to myself.

I was involved in the Allinger study you referred to.  The reference is:
L.R. Schmitz, N.L. Allinger, K.M. Flurchick, J. Comput. Chem. 9, 281(1988).
In that study we calculated step-wise heats of hydrogenation of barrelene.
The first was unusually large; implying barrelene is less stable than expected
for simple alkenes.  Note: this study used various empirical schemes from the
literature for estimating heats of formation from 6-31G*//3-21G calculations.

Later I developed another empirical schemes for estimating heats of formation
from 6-31G*//6-31G* calculations.  This gave similar results.  The reference
is:
L.R. Schmitz, Y.R. Chen, J. Comput. Chem. 15, 1437 (1994).

Finally, I have developed another scheme that uses MP2/6-31G**//6-31G*
energies as a starting point.  When applied to the heats of hydrogenation of
barrelene, this predicts that heat of hydrogenation of the first double bond
is still large.  However, the magnitude is reduced from what we calculated
using HF energies.  This has not been published yet but will be submitted
soon.

There are experimental heats of hydrogenation (in solution) available and
the results are similar to our calculated results.

If barrelene is antiaromatic, it would be less stable than expected for simple
alkenes.  However, the strain in these rings is an alternative explanation.

Larry Schmitz
Department of Chemistry
Marshall University
Huntington, WV 25705

schmitz $#at#$ marshall.edu  or chm001 $#at#$ marshall.wvnet.edu



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