Delocalized Pi Bond: Explanation and Examples

Delocalized pi bonds are those bonds that contain delocalized electrons among nuclei of the atoms. These bonds are situated below and above the sigma bonds. The p orbitals combine with each other. As a result of the overlapping of p orbitals, π bonds are formed.


Basic carbon skeletons are made up of sigma bonds. In some cases, there is a large pi framework that spread over atoms. This framework is responsible for the unexpected stability of polyunsaturated compounds like benzene.

Ethene (CH2=CH2)

Ethene contains sigma and pi bonds. It is chemically more interesting than ethane because of the pi bonds. The C-C π orbital is the highest occupied molecular orbitals (HOMO). This means it contains more electrons for reacting to other substances. The π orbital result from the overlapping of two 2p orbitals of separate carbon atoms. This combination can be in phase or out of phase. The in-phase combination account for the bonding molecular orbitals (π) and out-of-phase leads the anti-bonding molecular orbitals(π*).

delocalization of pi bond

The π bond contains two electrons. The filling of energy levels from the lowest to highest, So both electrons go into the BMO. In order to have a strong π bond, two atomic p orbitals overlap effectively. That means they must be parallel.

Benzene (C6H6)

Benzen has three strongly interacting double bonds. The π electrons in benzene as delocalized. That is not localized in specific double bonds between two particular carbon atoms. It is spread out over all six atoms in the ring.

delocalized pi bond of benzene

Concepts Berg

What are localized chemical bonds?

The bonds that are formed between only two nuclei and electrons are localized. Mostly they are sigma bonds.

What is the difference between localized and delocalized chemical bonds?

Localized bonds contain electrons between only two nuclei while delocalized bond contains electrons among more than two nuclei.

How to tell, in any given molecule, if a pi bond is localized or delocalized?

If a pi bond is present between two nuclei is localized. The pi bond located among more than two nuclei is delocalized.

Why do pi bond electrons delocalize?

the electron in pi bonds is delocalized because they are free to move between nuclei due to the resonance.

What are delocalized pi bonds?

Delocalized pi bonds are those bonds that contain free-moving electrons. It is because the p orbitals overlap in such a way that their electrons make contact with each other.

Does benzene have delocalized pi bonds or pi electrons?

Benzene has delocalized bonds and electrons. the pi orbitals make a donut shape above or below the sigma bond.

Do all compounds with a double bond have delocalized pi electrons?

Mostly, cyclo alkene has delocalized pi electrons.

Why sigma binds are always localized and pi bonds are always delocalized?

Sigma bonds are located between the two nuclei and they are head to head overlap. So electron will remain there but pi bonds are the result of side by overlapping. The pi-electron is free to move above and below the sigma bond.

How many electrons are delocalized in a carbonate ion?

Carbonate ions have four electrons that are delocalized.

How many sigma and pi bonds are there in CH4?

Methane has only sigma bonds. The structure of methane also shows that it contains carbon atoms single-bonded with the four hydrogen atoms.

What is the sigma and pi bond of benzene?

Benzene has 12 sigma bonds and 3 pi bonds.

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