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Friday, October 16, 2020

What is Pi-(π)Bond ?

According to Valance bond theory (VBT) by overlapping of atomic Orbitals three types of covalent bond formation take place.

(1) Sigma Bond:

(2) Pi (π)-Bond:

(3) Delta Bond

Pi(π) Bond:

(1) Pi (π) bond formed by sideways/lateral overlapping of pure atomic orbitals except Benzene where hybrid orbital formed π- bond.

(2)  Lateral overlapping is only partial, so bonds formed are weaker and hence more reactive than sigma bond (repulsion between nucleus is more as orbitals have to come much close to each other for pi bond formation).

For example-formation of oxygen molecule. Only Py and Pz of oxygen atom have unpaired electron in each orbital for bonding.

Electronic configuration of oxygen atom is 1s2,2s2,2Px2,Py1,Pz1

(3) Free rotation about a pi bond is not possible.

(4) pi bond is weaker than sigma bond .

(5) pi bond takes part in resonance.

(6) pi bond formed by pure or unhybrid orbitals.

Type of π- bond:

(1) Pπ-Pπ bond:

(2) Pπ-dπ bond:

(3) dπ-dπ bond:

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