Sigma bond and Pi bond

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Sigma bond
The bond which is formed by end to end  or axial overlapping of orbitals are called Sigma Bond.

Its bonding orbital consists of a single electron cloud symmetrical about inter nuclear axis.

Since, the overlapping along the axis is maximum, the bond formed is strong.

• Sigma-electrons are reffered as localized.
• Sigma-electrons are less reactive.
• Sigma bond can have independent existance.
• Groups or atoms with small size attached to it are torsially rotated about sigma-bond.
• Sigma-bonds help to determine the shape of molecule.

Pi-Bond

It is a weak covalent bond formed by side wise or lateral overlapping.

Pi bond is weak because of lateral overlapping of orbitals. The bonding consists of two electron clouds - one above and other below the plane of participating atoms.

• Pi-electrons are referred as delocalized.
• Pi-bonds are more reactive.
• Pi-bonds always exists with Sigma bonds.
• Groups or atoms attached to it are not rotated about this bond.
• Pi bonds does not effect the shape of the molecule.
• It is formed by pure orbitals.

How to find the pi and sigma bond in structures.

Sigma-bond -  The first bond made with any other atom. They are made from hybridized orbitals.

Pi-bond - Any 2nd or 3rd bond made with any other atom. They are made from left over p-orbitals.

Dry Ether In Wurtz Reaction

As we know that Wurtz Reaction is carried out with Sodium metal which is highly reactive. Hence, we have to select a solvent which will not react with Sodium. Thus, ether becomes the best choice. Similarly, the alkyl halide should also dissolve in the solvent. The Sodium should be insoluble in the solvent which can be easily removed and alkanes formed should remain in solution, therefore it requires an aprotic solvent as the medium of the reaction. Dry ether is a very good non-polar, aprotic solvent for this purpose. Hence Dry ether is used.