Alkynes contain two pi (π) bonds.
Understanding Alkynes and Pi Bonds
Alkynes are organic molecules characterized by the presence of at least one carbon-carbon triple bond (C≡C). This triple bond is composed of one sigma (σ) bond and two pi (π) bonds.
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Sigma (σ) bond: This is a single, strong bond formed by the direct overlap of atomic orbitals along the internuclear axis. In alkynes, the sigma bond is formed by the end-to-end overlap of sp-hybridized orbitals from each carbon atom.
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Pi (π) bonds: These are weaker bonds formed by the sideways overlap of p orbitals above and below (or to the sides of) the internuclear axis. Because the triple bond includes two such regions of overlap, alkynes have two pi bonds.
Structure of an Alkyne Triple Bond
| Bond Type | Description |
|---|---|
| Sigma (σ) | Formed by the direct, head-on overlap of sp hybrid orbitals. |
| Pi (π) | Formed by the sideways overlap of p orbitals above and below the sigma bond. |
| Pi (π) | A second pi bond, perpendicular to the first, also formed by p orbitals. |
Therefore, the triple bond in an alkyne consists of one strong sigma bond, providing the primary link between the carbon atoms, and two weaker pi bonds, contributing to the overall electron density and reactivity of the molecule.
