Which statement among the following is correct?

\(\pi \)-bond always exist with \(\sigma \)-bond

The correct answer is option 1. \(\pi \)-bond always exist with \(\sigma \)-bond.

\(\sigma\)-Bond and \(\pi\) -Bond

\(\sigma\)-Bond:

Formed by the head-on overlap of atomic orbitals along the internuclear axis (the line connecting the nuclei of the bonded atoms). Exists in all types of covalent bonds, including single bonds (e.g., \(C-C\), \(C-H\)). Represents the strongest type of covalent bond due to direct overlap between orbitals.

\(\pi\)-Bond:

Formed by the side-by-side overlap of p orbitals that are perpendicular to the internuclear axis. Found in double bonds (e.g., \(C=C\)) and triple bonds (e.g., \(C≡C\)) where there is a second bond between the same pair of atoms. Generally weaker than sigma bonds due to the less effective overlap of orbitals

Analyzing the Statements:

1. \(\pi\)-bond always exists with \(\sigma\)-bond:

This statement is true. In molecules with double or triple bonds, there is always at least one \(\sigma\)-bond along the internuclear axis and one or more \(\pi\)-bonds formed by the side-by-side overlap of p orbitals. For example, in ethene \((C=C)\), there is one \(\sigma\)-bond and one \(\pi\)-bond between the carbon atoms.

2. \(\pi\)-bond can exist independently:

This statement is false. \(\pi\)-bonds cannot exist independently without a corresponding \(\sigma\)-bond. They are always associated with a \(\sigma\)-bond in double and triple bonds. A \(\sigma\)-bond must be present first for the formation of a \(\pi\)-bond between the same pair of atoms.

3. \(\sigma\)-bond is weaker than \(\pi\)-bond:

This statement is false. \(\sigma\)-bonds are generally stronger than \(\pi\)-bonds because \(\sigma\)-bonds involve a more effective overlap of orbitals along the bond axis. \(\pi\)-bonds are weaker due to the side-by-side overlap of p orbitals, which is less effective in orbital overlap.

4. \(\pi\)-bond is less reactive than \(\sigma\)-bond:

This statement is false. Reactivity depends on various factors such as bond strength and electron density, not on whether a bond is \(\sigma\) or \(\pi\). Both \(\sigma\)- and \(\pi\)-bonds can participate in chemical reactions depending on the nature of the reaction and the atoms involved.

Conclusion:

Based on the definitions and characteristics of sigma and pi bonds, the correct statement among the options provided is option (1): \(\pi\)-bond always exists with \(\sigma\)-bond.

This statement accurately describes the relationship between sigma and pi bonds in molecules with double or triple bonds, where both types of bonds are present between the same pair of atoms. Therefore, option (1) is the correct answer.