Question

Which of the following statements is not correct for sigma- and pi- bonds formed between two carbon atoms?

• A. Sigma-bond is stronger than a pi-bond.
• B. Bond energies of sigma- and pi-bonds are of the order of 264 KJ/mol and 347 KJ/mol, respectively.
• C. Free rotation of atoms about a sigma bond is allowed but not in case of a pi-bond.
• D. Sigma-bond determines the direction between carbon atoms but a pi-bond has no primary effect in this regard.

Answer 1

The correct option is B Bond energies of sigma- and pi-bonds are of the order of 264 KJ/mol and 347 KJ/mol, respectively.

Sigma bond is a covalent bond resulting by end to end overlap of atoms, and its energy is stronger and the carbon atoms have free rotation because of head to head overlapping, due to its formation, it determines the direction of bond, intermolecular distance etc.

Pi bond is a bond formed due to side overlapping of the atoms and due to its side overlapping, the energy is weaker compared to sigma bond and the movement across the bond is not possible die to its rigid nature. It has no effect in determining the direction of the bond. The bond energy of the sigma bond and pi bonds are given in wrong order respectively, and thus the given sentence is not correct.

Because the bond energy of the sigma bond should be greater compared to the pi bond.