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Using the reaction electronic flux, a new tool aimed at identifying and characterizing the electronic activity taking place during a chemical process, the chelotropic and cycloaddition reactions of 1,3-butadiene with sulfur dioxide are revisited. The mechanisms of both reactions were studied within the framework of the reaction force analysis; the electronic activity determined through the reaction electronic flux was rationalized in terms of chemical events, bond forming or breaking processes, and polarization and transfer effects localized on the reactants species. The results show interesting features and differences between both the mechanisms; while the chelotropic path is driven by through space electrostatic interactions, the cycloaddition reaction is mainly driven by through bond electronic activity. The relation between these findings and the experimentally found kinetic (cycloaddition) and thermodynamic (chelotropic reaction) control is discussed. Int J Quantum Chem, 2012. © 2012 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Abstract: A theoretical study of the conformational dependence of energy and electronic properties of neutral and protonated histamine tautomers was performed with the aim of modelling its interaction with an hypothetical receptor. Analysis of chemical potential, electrophilicity, dipole moment, at the global level, as well as the dual descriptor por chemical reactivity, at local level, indicate that the π tautomer presents the right conformation and reactivity behavior to interact with the receptor. [Copyright &y& Elsevier]