Single Bonds as Neighboring Groups

The carbon-carbon single bond as a neighboring group.m... 

The Carbon-Carbon Single Bond as a Neighboring Group a. The 2-Norbornyl System. In the investigations to determine whether a C—C CT bond can act as a neighboring group, by far the greatest attention... 

Hydrolytic cleavage of single carbon-fluorine bonds generally requires activation by a neighboring group such as a carbonyl, sulfonyloxy, or olefinic bond or a negatively substituted aromatic group. 

In discussing nonclassical carbocations we must be careful to make the distinction between neighboring-group participation and the existence of nonclassical carbocations. ° If a nonclassical carbocation exists in any reaction, then an ion with electron delocalization, as shown in the above examples, is a discrete reaction intermediate. If a carbon-carbon double or single bond participates in the departure of the leaving group to form a carbocation, it may be that a nonclassical carbocation is involved, but there is no necessary relation. In any particular case, either or both of these possibilities can be taking place. 

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