In alkenes, the carbon atoms participating in the double bond undergo sp² hybridization, a key concept for understanding the geometry and reactivity of these molecules.
Hybridization Process
Formation: One s orbital and two p orbitals on a carbon atom hybridize to form three sp² orbitals.
Geometry: The sp² orbitals arrange themselves in a trigonal planar geometry around the carbon atom, with an angle of approximately 120° between them.
Sigma Bonds: Each carbon atom forms three σ bonds using its sp² orbitals: two with adjacent carbon or hydrogen atoms and one with the carbon atom sharing the double bond.
Pi Bond Formation
Unhybridized p Orbital: The p orbital not involved in sp² hybridization remains perpendicular to the plane of the sp² orbitals.
Double Bond Composition: The double bond in alkenes consists of one σ bond (from the overlap of sp² orbitals) and one π bond (from the side-to-side overlap of the unhybridized p orbitals).
Example: Ethene (C₂H₄)
Hybridization: Both carbon atoms in ethene are sp² hybridized.
Bonding: Each carbon forms two σ bonds with hydrogen atoms and one σ bond with the other carbon. The π bond between the carbon atoms arises from the overlap of their unhybridized p orbitals.