Chapter 7 ?2010, Prentice Hall Organic Chemistry, 7th Edition L. G. Wade, Jr. Structure and Synthesis of Alkenes Chapter 7 * Introduction Alkenes are hydrocarbon with carbon-carbon double bonds. Alkenes are also called olefins, meaning ?oil-forming gas?. The functional group of alkenes is the carbon-carbon double bond, which is reactive. Chapter 7 Chapter 7 * Sigma Bonds of Ethylene Chapter 7 Chapter 7 * Orbital Description Sigma bonds around the double-bonded carbon are sp2 hybridized. Angles are approximately 120? and the molecular geometry is trigonal planar. Unhybridized p orbitals with one electron will overlap forming the double bond (pi bond) . Chapter 7 Chapter 7 * Bond Lengths and Angles sp2 hybrid orbitals have more s character than the sp3 hybrid orbitals.