UNDERSTANDING DELOCALIZATION AND HYPERCONJUGATION IN TERMS OF (COVALENT AND IONIC) RESONANCE STRUCTURES
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Padeleimon KARAFILOGLOU*
Aristotle University of Thessaloniki, Faculty of Chemistry, Greece
Abstract
Electron transfer (from bonding to anti-bonding orbitals) effects, as delocalization and hyperconjugation, are translated into a language referring to resonance structures of covalent and ionic components of bonds. These effects are presented as examples destined to familiarize students with the translation of molecular orbital wave functions into the chemically meaningful language of resonance structures. ‘Structural multiplication tables’ are introduced as a pedagogical tool, allowing one to generate resonance structures in a pictorial manner. It is shown that the transfer of one electron from a bonding orbital,ωi,j (donor), to an anti-bonding one, ωk,l * (acceptor), creates an odd (an unpaired) electron in region (i,j) and another odd electron in region (k,l); the coupling of these two odd electrons provides the necessary covalent component(s) of the new bond(s) between the donor and the acceptor. [Chem. Educ. Res. Pract. Eur., 2002, 3, 119-127]