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Empirical force‐field and ab initio calculations on delocalized open chain cations
Author(s) -
Reindl Bernd,
Clark Timothy,
Schleyer Paul von R.
Publication year - 1997
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/(sici)1096-987x(19970115)18:1<28::aid-jcc4>3.0.co;2-1
Subject(s) - delocalized electron , ab initio , chemistry , ab initio quantum chemistry methods , resonance (particle physics) , computational chemistry , force field (fiction) , atomic physics , physics , molecule , organic chemistry , quantum mechanics
Force‐field calculations are reported for large delocalized cations. The results for the geometries, heats of formation, and π‐electron densities agree well with MP2(full)/6–31G * 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 π‐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 π‐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 π‐systems with ab initio data suggests that MMP2 can be used to study the influence of these interactions in cationic π‐systems too large to be calculated by correlated ab initio methods. © 1997 by John Wiley & Sons, Inc.