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Empirical force-field andab initio calculations on delocalized open chain cations

✍ Scribed by Reindl, Bernd; Clark, Timothy; Schleyer, Paul von R.

Publisher: John Wiley and Sons
Year: 1997
Tongue: English
Weight: 592 KB
Volume: 18
Category: Article
ISSN: 0192-8651
DOI: 10.1002/(sici)1096-987x(19970115)18:1<28::aid-jcc4>3.0.co;2-1

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✦ Synopsis

Force-field calculations are reported for large delocalized cations. The results for the geometries, heats of formation, and -electron densities agree well with Ž . MP2 full r6-31G* ab initio calculations. Both methods give similar results for the distortion of the carbon skeletons of unsubstituted cations by hyperconjugating methyl groups. Because of the SCF treatment of -interactions, the MMP2 force-field technique enables calculations of resonance energies in delocalized cations. The additional resonance stabilization produced by extending conjugation is directly related to the -charge on the carbon at which a vinyl group is substituted. The good agreement of MMP2 results for nonbonded resonance effects in large delocalized cationic -systems with ab initio data suggests that MMP2 can be used to study the influence of these interactions in cationic -systems too large to be calculated by correlated ab initio methods.

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