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Hyperconjugation - Practice Questions & MCQ

Edited By admin | Updated on Sep 25, 2023 25:24 PM | #NEET

Quick Facts

  • Hyperconjugation is considered one the most difficult concept.

  • 18 Questions around this concept.

Solve by difficulty

In which of the following compounds, the C - CI bond ionisation shall give most stable carbonium ion ?

Among the following compounds the one that is most reactive towards electrophilic nitration is:

Consider the following compounds   

Hyperconjugation occurs in:

Which one of the following groupings represents a collection of isoelectronic species?

(At. nos.: Cs-­55, Br­-35)

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 which accept the 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.

Study it with Videos

Hyperconjugation
Nomenclature of Compounds(Arenes) - 1
Application of Electrophile and Nucleophile

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Books

Reference Books

Hyperconjugation

Chemistry Part II Textbook for Class XI

Page No. : 355

Line : 42

Nomenclature of Compounds(Arenes) - 1

Chemistry Part II Textbook for Class XI

Page No. : 343

Line : 1

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