A bonding evolution analysis for the thermal Claisen rearrangement: an experimental and theoretical exercise for testing the electron density flow

Abstract

A comprehensive theoretical investigation of the thermal Claisen rearrangement of allyl vinyl ether (AVE) to allylacetaldehyde has been carried out. We present the use of the electron localization function (ELF) to monitor the bonding evolution aspects in the course of this thermal rearrangement and the results are compared with a photo-impulsive process where instantaneous vibration frequencies are monitored [I. Iwakura, Phys. Chem. Chem. Phys., 2011, 12, 5546-5555]. Our results reveal an asynchronous electron density rearrangement inasmuch that the breaking of the C3-O bond and the formation of C1-C5 do not take place simultaneously. We also demonstrate how the bonding evolution brings about the natural appearance of the curly arrows representing the electronic flow in molecular rearrangements. This holds the key to gaining an unprecedented insight into the mapping of the electron density flow while the bonds change throughout the reaction progress.

Are There Only Fold Catastrophes in the Diels–Alder Reaction Between Ethylene and 1,3-Butadiene?

“…Moreover, a description of changes of the topologically defined molecular structures as a response to the variation of control parameters can be addressed via the theory of elementary catastrophes. , It has been mainly exploited within both the QTAIM and ELF ,, frameworks. Within the so-called bonding evolution theory (BET) framework, the transformation of the topology of the ELF along a chosen reaction path (e.g., the intrinsic reaction coordinate (IRC) , ) are characterized in terms of Thom’s elementary catastrophes. ,,, The BET has a demonstrated capability for studying the evolution of the rearrangement of electron pairing (as measured by the ELF) along the reactive path, and hence, chemically significant events, including bond making/breaking processes, become naturally associated with specific structural stability domains (SSDs) separated by catastrophe bifurcations. ,,, BET has provided meaningful insights on an ever-increasing number of reactive processes related to problems in almost all fields of chemistry, , including, for instance, key questions on bonding and reactivity related to the activation of C–H bonds, proton/hydrogen transfer reactions, [4 + 2] cycloadditions, , [3 + 2] cycloadditions, , [1,3] dipolar cycloadditions, ,, the process of fixation of CO 2 by metal complexes, decarbonylation of unsaturated cyclic ketones, the nature of phase transitions for the group IV elements, the formation of hemiaminals, , Cope , and Claisen − rearrangements, the thermal decomposition of α-ketoesters, hydrometalation of acetylene, oxidative additions of ammonia to pincer complexes, the Curtis rearrangement, the catalytic Noyori hydrogenation, and the Wittig reaction . We stress that any chemical reaction can, in principle, be in such a way represented in terms of a precise sequence of catastrophic bifurcations associated with electron pairing topologies that enable a straightforward rationalization or interpretation of the evolution of the key chemical concept of bonding patterns. ,,, …”

Exploring The Sequence of Electron Density Along The Chemical Reactions Between Carbonyl Oxides And Ammonia/Water Using Bond Evolution Theory

“…However, the key questions that must be addressed to understand the nature of the molecular mechanisms remain related to fundamental chemistry: the distribution and the evolution of electron density along the reaction pathway. The bonding evolution theory, based on the changes described by Thom's catastrophe theory on the electron localization function topology along a given reaction path, is capable of unambiguously identifying the main chemical events happening throughout chemical reactions, [35–40] and generating the corresponding curly arrows to describe the reaction mechanism [41,42] …”

Unraveling the Bonding Nature Along the Photochemically Activated Paterno‐Büchi Reaction Mechanism

“…More specifically, we appeal to the topology analysis of the electron localization (ELF) function [23,[30][31][32] combined with Thom's catastrophe theory [33] as a theoretical background for elucidating underlying key bonding events. [20,28,[34][35][36][37][38][39] The ELF constitutes a measure of pair localization on the real-space, associated with seminal Lewis-like notions on the chemical bond. Notably, its topology in terms of basins of attractors and critical points provides a piece of valuable information about valence-shell structure representing essential concepts related to chemical thinking.…”