Physiker versus Organiker Views of Reaction “Mechanism”: How Natural Resonance Theory Bridges the Gap

• Eric D. Glendening ^[1] ; Steven D. Burke ^[2] ; John W. Moore ^[2] ; Frank Weinhold ^[2]
  1. [1] Indiana State University

     Indiana State University

     Township of Harrison, Estados Unidos

     
  2. [2] University of Wisconsin–Madison

     University of Wisconsin–Madison

     City of Madison, Estados Unidos

     
• Localización: Journal of chemical education, ISSN 0021-9584, Vol. 99, Nº 11, 2022, págs. 3702-3712
• Idioma: inglés
• Texto completo no disponible (Saber más ...)
• Resumen

  • Traditional physical chemistry conceptions of reaction mechanism are formulated in terms of stationary points of an Arrhenius-style “energy profile” that differs sharply (in purpose and form) from the corresponding Robinson-style “arrow-pushing” mechanistic conceptions of organic chemistry. We show here how these diverse “mechanistic” conceptions can be reconciled in a unified computational protocol based on a natural resonance theoretic (NRT) description of successive bond shifts between reactant and product bonding patterns. For pedagogical purposes, we employ a model SN2 halide exchange reaction described at a routine level of density functional theory, but the outlined NRT protocol involves no intrinsic dependence on theory level, reaction order, or perceived “elementary” character of the reaction. The NRT-based characterization of electronic bond-shifts provides a rigorous criterion for judging the correctness of a proposed arrow-pushing mechanism, while also adding rich details of the multiple electronic “transitions” that may accompany a chemical transformation along the reaction pathway, even if the associated energy profile is barrierless or marked by a single maximal “transition state” feature.