Questions tagged [hyperconjugation]

Hyperconjugation involves the donation of electrons from a filled orbital (commonly the bonding C-H sigma molecular orbital) into an adjacent/partially occupied p-orbital (for instance an adjacent carbocation) leading to stabilisation. The tag should be applied to questions where hyperconjugation is involved, even if the question does not explicitly refer to it.

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Inductive effect and hyperconjugation - one elephant, different parts?

Are the inductive effect and hyperconjugation both different ways of looking at the same phenomenon - i.e. methyl groups donate negative charge for example. Inductively we can argue that carbon is of ...
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3answers
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What is hyperconjugation?

What is hyperconjugation and how do you know if there is hyperconjugation in a compound? Which orbitals are involved in hyperconjugation?
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2answers
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The effect of hyperconjugation on the stability of alkenes with MO theory

Hyperconjugation stabilizes carbocations and that makes sense because electrons are given to the empty p orbital. But how does it stabilize alkenes? Can molecular orbital theory be used to explain it?...
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1answer
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Why are double bonds at more substituted carbon more stable?

That $\ce{C=C}$ bonds are more stable at more substituted carbon atoms is a common argument used throughout Clayden et al., but is never actually explained (at least not in the first 21 chapters). ...
2
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1answer
6k views

Why is a C–D bond stronger than a C–H bond?

I have heard that the carbon–deuterium bond is stronger than the carbon–hydrogen bond. What are the possible reasons for it? Is this also the reason that C–H bonds participate more in hyperconjugation ...
32
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1answer
794 views

Why does hyperconjugation help for ring cleavage?

The question was to rationalize it the ring cleavage happens concerted or non-concerted. The papers "The Mechanism of the Thermal Decomposition of 1-Pyrazolines and Its Relationship to ...
10
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1answer
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What is the directive influence of the tert-butyl group in electrophilic aromatic substitution?

We know that hydrocarbon side-chains on a benzene ring influence electrophilic substitutions by directing the incoming electrophile to attack at ortho and para positions. The following ...
9
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2answers
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Why is the eclipsed conformer more stable than the bisected conformer in 1-butene?

I have just started learning conformational analysis, and a major doubt came into my mind. In simple alkanes such as ethane, the staggered conformer is much more stable than the eclipsed conformer. ...
4
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1answer
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Stabilisation of carbocations through hyperconjugation

Our teachers told us that greater the number of alpha H, greater is the stability of carbocation. But consider this: $\ce{CH3CH2+}$ and. $\ce{CH3CH2CH2+}$ The first one has 3 alpha H ...
6
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2answers
646 views

Hyperconjugation in ethane conformers

I refer you to this set of presentation slides. On slide 8, the author explains the preference for the staggered conformation of ethane by saying that there is a favourable hyperconjugative ...
2
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1answer
127 views

Hyperconjugation involving other bonds

Hyperconjugation is often illustrated with C-C and C-H bonds donating electron density to the p orbital in the adjacent carbon atom. Since the concept revolves around sigma bonding orbitals donating ...
2
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1answer
85 views

Hyperconjugation and the stability of alkenes

Clearly, this issue has been touched on here and here. However, I would like to raise a new point on the issue. I have always thought that stabilisation of the $\ce {C=C}$ $\pi$ bond via ...
2
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0answers
169 views

Confusion about gauche effect

This recent question about the gauche effect led me to read this rather older answer. The problem is that I notice I am still confused. To take the case of 1,2 difluoroethane, I drew these orbitals: ...
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2answers
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How does hyperconjugation lead to the directing properties of alkyl group?

I have explained how hyperconjugation leads to the directing properties of alkyl groups below. Carbon joining substituent now need only single bond. So if we remove one bond between $\ce{H-C}$ along ...