Conjugation---Hyperconjugation

Conjugation has been discussed so far only as something taking place between p orbitals in a n system. However, it is possible to consider the conjugation of 

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The interaction between a and -it electrons of single and multiple bonds (or the -tt electrons in the aromatic ring) is usually interpreted (Baker, 1952) as a, -conjugation (hyperconjugation). In this process the hydrocarbons become stronger protolytes. For example, the acidic and basic behaviour of propene and toluene are more pronounced than the corresponding properties of ethylene and benzene. 

At present then, it is uncertain to what extent these three factors conjugation/hyperconjugation, hybridization, and polar attractions, (in addition to small steric interaction energies) are responsible for variations in hydrogenation heats. 

Direct Estimate of Conjugation, Hyperconjugation, and Aromaticity with the Energy Decomposition Analysis Method... 

Figure 12.1 Representative examples of compounds exhibiting conjugation, hyperconjugation, and aromaticity.

Luo, Y. R. (2003). Bond Dissociation Energies of Organic Compounds, CRC Press. Caveat one has to be careful not to attribute the BDE trends solely to the orbital size effects. Other factors (e.g. polarization, hybridization, conjugation, hyperconjugation, non-bonding electron repulsion) are in play as well as will be discussed in more detail in the subsequent parts of this hook. 

Three types of delocalization conjugation, hyperconjugation, and o-conjugation... 

Model 2 p Orbital to [Pg.202]

Electron donation by an alkyl group can be considered an inductive or a pseudo-resonance effect (See hyper conjugation). Hyperconjugation cannot be demonstrated with second-order resonance structures. 

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