Abstract
This chapter develops a qualitative methodology for constructing states from their valence bond (VB) building blocks. The essence of the method is a mixing-diagram of the type used in qualitative molecular orbital (MO) theory. The method is used initially to describe states for representative species; a covalent bond, species which possess an average of one electron per site (e.g., allyl radical, etc.,) and mixed-valence species (i.e., molecular ions). Then the method is applied to piece up potential energy profiles for two prototypical reactions (the exchange reactions of H and H−). Finally, the conclusions are generalized to treat complex organic reactions, such as spin-transfer reactions (e.g., radical additions) electrophile-nucleophile combinations, cycloadditions and so on. The origins and variations of barriers and the importance of the quantum mechanical resonance energy of the transition state are discussed.
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Shaik, S.S. (1989). A Qualitative Valence Bond Model for Organic Reactions. In: Beltrán, J., Csizmadia, I.G. (eds) New Theoretical Concepts for Understanding Organic Reactions. NATO ASI Series, vol 267. Springer, Dordrecht. https://doi.org/10.1007/978-94-009-2313-3_7
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DOI: https://doi.org/10.1007/978-94-009-2313-3_7
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