Question

How many sigma and Pi bonds are in ${\mathrm{HCONHCH}}_3$?

Answer 1

Sigma and pi bond in ${\mathrm{HCONHCH}}_3$ ($\mathrm{N}-\mathrm{Methylformamide}$)

• The covalent bond formed by the coaxial overlap of atomic orbitals is called sigma bonding. for example, methane molecules contain 4 C-H sigma bonding. It is represented by the Greek letter $\mathrm{\sigma }$.
• The covalent bond formed by the lateral overlap of atomic orbitals is called a pi bond. For example, an ethylene molecule contains 5 sigma bonding and 1 pi bonding in it. It is represented by $\mathrm{\pi }$.

1. To count sigma and pi bonds, first, you need to know how many single, double and triple bonds are present in the molecule.
2. A single bond contains one sigma bond.
3. A double bond contains one sigma and one pi bond.
4. A triple bond contains one sigma and 2 pi bonds.
5. There are four $\mathrm{C}-\mathrm{H}$ sigma bonds, two $\mathrm{C}-\mathrm{N}$ sigma bond, one $\mathrm{N}-\mathrm{H}$ sigma bond, and one $\mathrm{C}=\mathrm{O}$ pi bond.
6. So there are 8 sigmas and 1 pi bonds.

A single bond contains one sigma bond (direct head-on overlap of orbitals).

A double bond contains one sigma bond and one pi bond (side-on overlap of p orbitals).

A triple bond contains one sigma bond and 2 pi bonds.

The triple bond consists of a sigma bond and two pi bonds. The sigma bond is formed by the head-on overlap of two sp orbitals. The pi bonds are formed by the side-on overlap of 2p orbitals.

There are 8 sigma bonds between hydrogen, carbon, oxygen, and nitrogen. While oxygen is doubly bonded to carbon so it means that there is an additional pi bond between carbon and oxygen. Therefore there are 8 sigma bonds and 1 pi bond.

Hence the number of sigma and Pi bonds are in ${\mathrm{HCONHCH}}_3$ 8 and 1 respectively.