Quantitative valence bond computation of a curve crossing diagram for a model SN2 reaction, H- + CH3H′ → HCH3 + H′-

Gjergji Sini, Sason S. Shaik*, Jean Michel Lefour, Gilles Ohanessian, Philippe C. Hiberty

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

40 Scopus citations

Abstract

A quantitative avoided crossing diagram for the model SN2 reaction, Hl- + CH3Hr. → HlCH3 + Hr-, is computed by using a VB method based on local fragment orbitals. The essential parameters of curves are quantified at the 6-31G*+D level. The vertical electron-transfer energy gap, G, is 174 kcal/mol. The height of the crossing point (relative to H- + CH4) is 42% of G. The quantum mechanical resonance energy of the transition state, i.e., the avoided crossing interaction, is 15.9 kcal/mol. The barrier of 56.8 kcal/mol is computed as the difference between the height of the crossing point and the avoided crossing interaction. All these parameters show insignificant basis set dependence and support previous estimations of these parameters which formed the crucial hypotheses for the use of the avoided crossing model to discuss reactivity trends.

Original languageEnglish
Pages (from-to)5661-5665
Number of pages5
JournalJournal of Physical Chemistry
Volume93
Issue number15
DOIs
StatePublished - 1989
Externally publishedYes

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