Which of the following statements is not correct for sigma and pi-bonds formed between two carbon atoms:
- Sigma-bond is stronger than a pi-bond
- Bond energies of sigma- and pi-bonds are of the order of 264 KJ/mol and 347 KJ/mol, respectively
- Free rotation of atoms about a sigma bond is allowed but not in case of a pi-bond
- Sigma-bond determines the direction between carbon atoms but a pi-bond has no primary effect in this regard
The Correct Option is B
Solution and Explanation
Option (B) is not correct. The bond energies of sigma- and pi-bonds are not of the order mentioned in option (B).
In reality, sigma bonds are generally stronger than pi bonds. The typical bond energy for a sigma bond is higher than that for a pi bond. The values for bond energies can vary depending on the specific compounds and circumstances, but the order of bond strength is generally sigma > pi.
So, 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
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Concepts Used:
Tetravalence of Carbon
The valency of carbon is - 4 (Four). Tetravalency of Carbon is the ability of carbon to bond with the other 4 atoms of carbon or atoms of other monovalent elements. The term 'Tetra' means ‘Four’ and the term ‘Valency’ means ‘Combining capacity’. When carbon is said to be Tetravalent, it means that the valency of carbon is 4 and it can form 4 covalent bonds with other atoms. Catenation is the ability of carbon to form bonds of covalent nature with other carbon atoms.
Electronic Configuration and Valency of Carbon:
The valency of carbon can be described by understanding the Electronic Configuration of Carbon. There are two types of the electronic configurations of carbon:
- Carbon at ground state: A ground-state atom is an atom in which the total energy of electrons cannot be let down by transferring one or more electrons to different orbitals. In the ground state carbon, all electrons are in the lowest possible energy levels. Although carbon has 4 electrons, it can make only 2 bonds because it has only 2 unpaired electrons in ground state carbon.
- Carbon at excited state: A carbon is said to be in an animated state when the total energy of electrons can be taken down by transferring an electron from the 2P orbital to the 2S orbital. In the animated state of carbon, there are 4 unpaired electrons so it can make bonds with 4 other atoms.