Allyl inductive, hyperconjugative

The 1,3-dipolar cycloadditions offluonnatedallenes provide a rich and varied chemistry Allenes, such as 1,1-difluoroallene and fluoroallene, that have fluorine substitution on only one of their two cumulated double bonds are very reactive toward 1,3-dipoles Such activation derives from the electron attracting inductive and hyperconjugative effects of the allylic fluorine substituent(s) that give nse to a considerable lowering of the energy of the LUMO of the C(2)-C(3) n bond [27]... 

The greater the number of alkyl substituents bonded to the positively charged carbon, the more stable the carbocation will be. The order of relative stability of carbocations is tertiary benzyhc > allylic secondary > primary vinyl> phenyl. The nature of electron release by alkyl groups is not very clear. It may be an inductive effect, a resonance effect (hyperconjugation), or a combination of the two. When we refer to the inductive effect of the alkyl groups, it should be clear that this might well include a contribution from hyperconjugation. 

In allyl halide, both inductive and hyperconjugative are electron withdrawing and thus rate reducing at either the p or the y position. 

The rate-retarding effect of the allylic halogen substituent is accounted both for inductive and hyperconjugation. Both of these are electron withdrawing and therefore, rate reducing at either the p position or y position [10]. 

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