Hybridization resonance

The ally carbocation is an example of an intermediate whose structure has been extensively investigated by MO methods. The hybridization/resonance approach discussed earlier readily rationalizes some of the most prominent features of the allyl carbocation. The resonance structures suggest a significant stabilization and imply that the molecule would be planar in order to maximize the overlap of the n system. 

Know the meaning of Kekule structure, benzene resonance hybrid, resonance or stabilization energy. 

During my early years as an assistant professor at the University of Kentucky, I demonstrated the synthesis of a simple quinone methide as the product of the nucleophilic aromatic substitution reaction of water at a highly destabilized 4-methoxybenzyl carbocation. I was struck by the notion that the distinctive chemical reactivity of quinone methides is related to the striking combination of neutral nonaromatic and zwitterionic aromatic valence bond resonance structures that contribute to their hybrid resonance structures. This served as the starting point for the interpretation of the results of our studies on nucleophile addition to quinone methides. At the same time, many other talented chemists have worked to develop methods for the generation of quinone methides and applications for these compounds in organic syntheses and chemical biology. The chapter coauthored with Maria Toteva presents an overview of this work. 

The two resonance structures that contain an intact aromatic ring and place a negative charge on an O atom are major contributors to the hybrid. Resonance stabilizes phenoxide but not as much as... 

Hunsdiecker reaction, 341 Hybridization, 17 Hybrid orbital number, 17, 18, 32 Hybrid, resonance, 24 Hydration of cyclohexane derivatives, 191 Hydrazine, 4 Hydride shift, 93 Hydroboration, 95 Hydroboration-oxidation, 258, 270 Hydrocarbons, cyclic, 162 unsaturated, 87 Hydrogenation of alkenes, 57 Hydrogen bond, 22 Hydroperoxides in ethers, 284 Hydroquinone, 430 Hydroxy acids, 344... 

Draw contributing resonance structures and a hybrid resonance structure that explain two related facts the carbon—oxygen bond distances in the acetate ion are the same, and the oxygens of the acetate ion bear equal negative charges. 

This paper attracted Pauling s attention, who recognized that the Heitler-London procedure could not only be extended to larger molecules but also serve as a bridge between Lewis classical idea of chemical bond and the new quantum theory. In a series of papers ", where he introduced the concepts of hybridization, resonance, electronegativity, etc., and also in a famous book that influenced many generations of chemists, Pauling developed his ideas which formed the basis of the classical Valence-Bond theory. 

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