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+ Hyperconjugation
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Laiba Athar

Electron density in benzene ring

Michael J. McFadden  Follow

Well, tetrahydrocannabinol, you said it correct only the correct reason/explanation is hyperconjugation only.More the number of (alpha) hydrogen atoms on a C=C [isolated as in alkenes or in resonance as in benzene], more the possibility of hyperconjugation.

In benzene, this will shift the electron density from C-H bond of CH3 group towards the ring, making it electron rich.

Contrary to what could have been thought from +I effect of corresponding alkyl groups on the ring, hyperconjugation is more in CH3.

Since hyperconjugation involves complete shifting of electron from valence shell of atoms to the other, it is more "effective" that INDUCTIVE which just pushes electron little more towards more EN (more correctly, towards group with more -I) atom.Hyperconjugation in alkyl benzenes

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George Warner  Follow
Both C-C and C-H bonds can act as hyperconjugative donors. So your reasoning is not justified.More
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Jim Ashton  Follow
@Jan even if this would be a mesomeric structure (I never seen an actual sigma bond shifted while describing mesomeric structures) it doesnt make sense and is a mesomeric structure that shouldnt be used since its extremly far away from the actual structure. Hyperconjugation is too weak to justify such a form.More
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John Hubbling  Follow
-butylbenzene has the highest electron density so there More
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Eric Weatherby  Follow
First of all: C-C bonds are able to engage in hyperkonjugation, so "NO hyperconjugation possible" is just wrong. And Second: the drawing is terribly wrong, since no bonds are broken in case of hyperconjugation, and for hyperconjugation you need a certain orientation of the orbitals to each other, for a methyl group only one CH bond can really engage in hyperconjugation, the other two arent aligned very well.More
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Geoff Richardson  Follow
connected by More
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