1,3 dipoles: Valence Bond study of their diradical character and reactivity toward alke(y)nes
B. Braïdaa, S. E. Galembeckb, C. Walterc, B. Engelsc, P. C. Hibertyd
aLaboratoire de Chimie Théorique - UMR 7616 UPMC & CNRS - Paris, France.
bDepartamento de Química, Universidade de São Paulo, Brazil.
cInstitut für Organische Chemie, Würzburg, Germany.
dLaboratoire de Chimie Physique, Université Paris Sud XI, France.
Mercredi 29 Novembre 2017, 11h00
bibliothèque LCT, tour 12 - 13, 4ème étage
Ozone and its sulfur-substituted isomers, prototype examples of 1,3-dipoles, are studied by means of the Breathing Orbital Valence Bond (VB) ab initio method, with the aim of estimating their controversial diradical characters. All 1,3-dipoles can be described in terms of three major VB structures, one diradical and two zwitterionic ones, out of the six structures forming a complete basis. It will be shown that the VB-calculated weight of the diradical structure of a molecule qualifies itself as a quantitative measure of diradical character, and not only an indicator of tendencies.[1] The reactivity of a selection of nine 1,3-dipoles toward ethylene and acetylene, as prototype reactions of 1,3-dipolar cycloaddition, will then be considered. It will be shown that the diradical character of 1,3-dipoles is a critical feature to favor 1,3-dipolar cycloaddition, and a new mechanism for 1,3-dipolar cycloaddition proposed.[2]
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References :
[1] B. Braïda, S. E. Galembeck and P. C. Hiberty, Submitted.
[2] B. Braïda, C. Walter, B. Engels and P. C. Hiberty J. Am. Chem. Soc. 2010, 132, 7631.