Chemical potential and reaction electronic flux in symmetry controlled reactions

• Published in: Journal of computational chemistry Vol. 37; no. 19; pp. 1794 - 1800
• Main Authors: Vogt-Geisse, Stefan, Toro-Labbé, Alejandro
• Format: Journal Article
• Language: English
• Published: United States Blackwell Publishing Ltd 15.07.2016; Wiley Subscription Services, Inc
• Subjects: Approximation; Chemical bonds; Chemical reactions; conceptual DFT; denisty functional theory; electronic chemical potential; reaction electronic flux; Symmetry; denisty functional theory; conceptual DFT; symmetry; reaction electronic flux; electronic chemical potential
• ISSN: 0192-8651; 1096-987X
• DOI: 10.1002/jcc.24394

In symmetry controlled reactions, orbital degeneracies among orbitals of different symmetries can occur along a reaction coordinate. In such case Koopmans' theorem and the finite difference approximation provide a chemical potential profile with nondifferentiable points. This results in an ill‐defined reaction electronic flux (REF) profile, since it is defined as the derivative of the chemical potential with respect to the reaction coordinate. To overcome this deficiency, we propose a new way for the calculation of the chemical potential based on a many orbital approach, suitable for reactions in which symmetry is preserved. This new approach gives rise to a new descriptor: symmetry adapted chemical potential (SA‐CP), which is the chemical potential corresponding to a given irreducible representation of a symmetry group. A corresponding symmetry adapted reaction electronic flux (SA‐REF) is also obtained. Using this approach smooth chemical potential profiles and well defined REFs are achieved. An application of SA‐CP and SA‐REF is presented by studying the Cs enol‐keto tautomerization of thioformic acid. Two SA‐REFs are obtained, JA′(ξ) and JA′′ (ξ). It is found that the tautomerization proceeds via an in‐plane delocalized 3‐center 4‐electron O‐H‐S hypervalent bond which is predicted to exist only in the transition state (TS) region. © 2016 Wiley Periodicals, Inc. The proposed symmetry adapted electronic fluxes for the tautomerization of thioformic acid. The major electronic changes take place in the molecular plane, which is represented by JA′′(ξ), while the changes in the π‐cloud ( JA′′(ξ)) are of less breadth.