open access

https://hdl.handle.net/2115/63104

Orbital Energy-Based Reaction Analysis of S(N)2 Reactions

英語

reaction path search

2016-09

MDPI

Computation

4(3)

23

An orbital energy-based reaction analysis theory is presented as an extension of the orbital-based conceptual density functional theory. In the orbital energy-based theory, the orbitals contributing to reactions are interpreted to be valence orbitals giving the largest orbital energy variation from reactants to products. Reactions are taken to be electron transfer-driven when they provide small variations for the gaps between the contributing occupied and unoccupied orbital energies on the intrinsic reaction coordinates in the initial processes. The orbital energy-based theory is then applied to the calculations of several S(N)2 reactions. Using a reaction path search method, the Cl- + CH3I -> ClCH3 + I- reaction, for which another reaction path called "roundabout path" is proposed, is found to have a precursor process similar to the roundabout path just before this S(N)2 reaction process. The orbital energy-based theory indicates that this precursor process is obviously driven by structural change, while the successor S(N)2 reaction proceeds through electron transfer between the contributing orbitals. Comparing the calculated results of the S(N)2 reactions in gas phase and in aqueous solution shows that the contributing orbitals significantly depend on solvent effects and these orbitals can be correctly determined by this theory.

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2079-3197