Analyse topologique de la densité électronique dans les réactions de cycloaddition [3+2] à l'aide de la Bond Evolution Theory

Abstract

In this thesis work, we have showed the progress that has been made towards gaining an understanding of the molecular mechanism of 32CA reactions using the Bonding Evolution Theory (BET), as a combination of topological analysis of the Electron Localization Function (ELF) and Thom’s catastrophe theory. By analyzing in detail the flow of electron density along the reaction pathway of four 32CA cycloadditions reactions, as case study, the nature of the molecular mechanisms has been characterized. The results of the present study provide : i) a deep insight on the reaction mechanism, based on the electron density rearrangements given by the Structural Stability Domain (SSD), and their connection with the bond breaking/forming processes along the reaction pathway, ii) a curly arrow representation of the whole reaction mechanism, in which four consecutive chemical events, associated to two transformations of double (triple for nitrile oxide) to single (double) bonds and two bond-forming processes (C−C and C−O bonds) are presented along the reaction pathway, iii) an analysis of how curly arrows meet electron density transfers in chemical reaction mechanisms, iv) how the Lewis structure can be recovered, and v) based on the structural stability domains of BET study along the intrinsic reaction coordinate, a new synchronicity index is proposed that allow us making some statements about the validity and limitations of the use of other criteria, such as geometry, bond order, and charge transfer at the transition structure for classifying and quantifying the (a)synchronicity of the 32CA reaction mechanisms and therefore the nature of the reaction mechanism.