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Hyperconjugation - Practice Questions & MCQ
Edited By admin | Updated on Sep 18, 2023 18:35 AM | #JEE Main
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39 Questions around this concept.
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IUPAC name of the following compound is
The compound which has one isopropyl group is:
The IUPAC name for
Arrange the following nucleophile in decreasing order of their nucleophilicity
1) $\mathrm{CH}_3-\mathrm{CO}-\mathrm{O}^{-}$
2) $\mathrm{CH}_3-\mathrm{O}^{-}$
3) $C N^{-}$
Which of the following alkane is most stable
Hyperconjugation involves delocalisation of ______.
(i) electrons of carbon-hydrogen bond of an alkyl group directly attached to an atom of unsaturated system.
(ii) electrons of carbon-hydrogen bond of alkyl group directly attached to the positively charged carbon atom.
(iii) -electrons of carbon-carbon bond
(iv) lone pair of electrons
Which one of the following groupings represents a collection of isoelectronic species?
(At. nos.: Cs-55, Br-35)
The compound which will have the lowest rate towards nucleophilic aromatic substitution on treatment with OH-is
The correct order of statbility for the following alkoxides is:
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Use NowThe electrophile, $E^{\oplus}$ attacks the benzene ring to generate the intermediate $\sigma$ - complex. Of the following, which $\sigma$-complex is of lowest energy?
Concepts Covered - 3
Hyperconjugation
Hyperconjugation is a general stabilising interaction. It involves delocalisation of σ electrons of C—H bond of an alkyl group directly attached to an atom of unsaturated system or to an atom with an unshared p orbital. The σ electrons of C—H bond of the alkyl group enter into partial conjugation with the attached unsaturated system or with the unshared p orbital. Hyperconjugation is a permanent effect.
To understand hyperconjugation effect, let us take an example of CH3CH2+(ethyl cation) in which the positively charged carbon atom has an empty p orbital. One of the C-H bonds of the methyl group can align in the plane of this empty p orbital and the electrons constituting the C-H bond in plane with this p orbital can then be delocalised into the empty p orbital as shown in the figure given below:
This type of overlap stabilises the carbocation because electron density from the adjacent σ bond helps in dispersing the positive charge.
In general, greater the number of alkyl groups attached to a positively charged carbon atom, the greater is the hyperconjugation interaction and stabilisation of the cation. Thus, we have the following relative stability of carbocations:
Hyperconjugation is also possible in free radicals, alkenes and alkylarenes.
In general, greater the number of hyperconjugative structures, greater is the stability.
Nomenclature of Compounds(Arenes) - 1
The IUPAC names and common names of some of the compounds are given below:
IUPAC name - Methylbenzene
Common name - Toluene
IUPAC name - Ethenylbenzene
Common name - Styrene
IUPAC name - 2-Methylphenol
Commoon name - o-Cresol
Application of Electrophile and Nucleophile
Electrophiles: These are those species that accept electrons. Usually, they are positively charged species.
Nucleophiles: These are those species which has a tendency to donate electrons pairs or react at electron-poor sites.
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Hyperconjugation
Nomenclature of Compounds(Arenes) - 1
Application of Electrophile and Nucleophile"Stay in the loop. Receive exam news, study resources, and expert advice!"
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