Hyperconjugation sacrificial

Hyperconjugation of the kind described above is called sacrificial hyperconjugation, since there is one less real bond in structures like II than in I. In contrast, the kind of... 

At present, there is no evidence for sacrificial hyperconjugation in neutral hydrocarbons. The concept of hyperconjugation is also applied to CARBENIUM ions and radicals, where the interaction is now between o-bonds and an unfilled or partially filled n or p-ORBiTAL. A contributing structure illustrating this for the tert-butyl cation is ... 

In this type of hyperconjugation, donor and acceptor interactions are balanced, and often there is no dominating effect. As a result, the importance of sacrificial hyperconjugation in neutral hydrocarbons has been initially controversial. However, now the effects of hyperconjugation on X-ray geometries of nentral molecules are well-documented. °... 

To summarize Baker and Nathan observed that hyperconjugation appeared to occur to a greater extent when H was the nonbonded fragment in the sacrificial valence bond form, compared with the case where CHJ was the fragment. This difference between the two (called the Baker-Nathan effect) was not very great in any case and was subsequently shown to be due to a solvation effect. This has led to the statement... 

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