Sigma bond and pi bond is very basics of organic chemistry. Nature of sigma bond as well as pi bond
- The bond formed by coaxial or internuclear overlapping of orbitals is called a sigma bond. The bond formed by lateral or sidewise overlapping of orbitals is called a Pi bond.
- Sigma bond consists of single electron cloud which is symmetrical about the internuclear axis. Pi bond consists of two electron clouds, one above and below the plane of participating atoms.
- In sigma bond formation a large amount of energy is evolved as compared to pi bond.
- In sigma bond, the overlapping is along the internuclear axis, the maximum overlapping takes place between two orbitals. Hence the bond formed is stronger. The energy of carbon-carbon sigma bond is 80 kcal.
pibond, overlapping of orbitals is lateral or sidewise. Hence the overlapping is a partial and resultant bond formed is weaker as compared to sigma bond. The energy of carbon-carbon pi bond is about 65 kcal.
Read also Properties of Noble Gases
- Sigma electrons are localized electrons because they are held by a strong force of attraction due to maximum overlapping. On the other hand, pi electrons are
referredas delocalized (mobile) electrons. These electrons can be easily polarized by the external charge.
- The atom or groups of atoms attached to sigma bond rotate (size of the molecule should be small). The atom or groups of atoms attached to the pi bond are not free to rotate. It is due to the resistance of the pi bond to rotate.
- Sigma bonds are less reactive while pi bonds are more reactive. Because sigma bonds are stronger due to coaxial overlapping hence a large amount of energy is required to break the bonds.
- Sigma bond can exist independent of the pi bond. On the other hand, pi bond exists along with a sigma bond.
- The shape of the molecule is determined by the presence of sigma bonds. The shape of molecules is not affected by pi bonds.