Pi bond

Definition

A pi bond is a type of covalent bond that occurs when two atomic orbitals overlap sideways, allowing for the sharing of electron density above and below the bond axis. This bonding interaction is essential in the formation of double and triple bonds, alongside sigma bonds, and plays a significant role in the geometry and reactivity of molecules.

5 Must Know Facts For Your Next Test

1. Pi bonds are typically found in double and triple bonds; in a double bond, one is a sigma bond and one is a pi bond, while in a triple bond, there is one sigma and two pi bonds.
2. The electron density in a pi bond is concentrated above and below the plane of the atoms involved, which allows for greater molecular flexibility.
3. Unlike sigma bonds, which allow for free rotation around the bond axis, pi bonds restrict rotational freedom due to their lateral overlap.
4. Pi bonds are generally weaker than sigma bonds due to their sideways overlap; this makes them more reactive and easier to break during chemical reactions.
5. In molecules with multiple bonds, such as alkenes and alkynes, the presence of pi bonds influences their reactivity and physical properties, like boiling points and polarity.

Review Questions

• How does the formation of pi bonds influence the geometry of molecules?
  • The formation of pi bonds affects molecular geometry because they restrict rotation around the bond axis. This restriction leads to specific geometrical arrangements, such as planar configurations in alkenes where double bonds are present. The presence of pi bonds also contributes to the overall shape of molecules, influencing angles between other atoms bonded through sigma bonds.
• Compare and contrast pi bonds with sigma bonds regarding their formation and strength.
  • Pi bonds differ from sigma bonds in their formation; while sigma bonds result from head-on overlaps of atomic orbitals, pi bonds arise from the sideways overlap of p orbitals. Additionally, sigma bonds are generally stronger due to their direct overlap, allowing for greater electron density between the nuclei. In contrast, pi bonds are weaker because they rely on lateral overlap, which leads to less effective electron sharing.
• Evaluate the role of pi bonds in determining the reactivity of organic compounds such as alkenes and alkynes.
  • Pi bonds significantly influence the reactivity of organic compounds like alkenes and alkynes due to their relative weakness compared to sigma bonds. The presence of these unsaturated bonds makes alkenes and alkynes more susceptible to addition reactions, as reagents can easily attack the electron-rich regions above or below the bonding plane. This characteristic plays a critical role in organic synthesis and reactions, making compounds with pi bonds key players in various chemical transformations.

Related terms

sigma bond:

A sigma bond is a type of covalent bond formed by the head-on overlap of atomic orbitals, characterized by a cylindrical symmetry around the bond axis.

hybridization: Hybridization is the process by which atomic orbitals mix to form new hybrid orbitals that are used to create covalent bonds, influencing molecular geometry.

double bond: A double bond consists of one sigma bond and one pi bond, resulting in a stronger bond between two atoms compared to a single bond.