Organic Chemistry,6th Edition L.G.Wade,Jr. Chapter 7 Structure and Synthesis of Alkenes
Chapter 7 Structure and Synthesis of Alkenes Organic Chemistry, 6th Edition L. G. Wade, Jr
Introduction Hydrocarbon with carbon-carbon double bonds ·Sometimes called olefins,“oil- forming gas” Chapter 7 2
Chapter 7 2 Introduction • Hydrocarbon with carbon-carbon double bonds • Sometimes called olefins, “oilforming gas
Functional Group Pi bond is the functional group. More reactive than sigma bond. Bond dissociation energies: >C=C BDE 611 kJ/mol >C-C BDE -347 kJ/mol >Pi bond 264 kJ/mol => Chapter 7 3
Chapter 7 3 Functional Group • Pi bond is the functional group. • More reactive than sigma bond. • Bond dissociation energies: ➢C=C BDE 611 kJ/mol ➢C-C BDE -347 kJ/mol ➢Pi bond 264 kJ/mol =>
Orbital Description Sigma bonds around C are sp2 hybridized. Angles are approximately 120 degrees. No nonbonding electrons. Molecule is planar around the double bond. Pi bond is formed by the sideways overlap of parallel p orbitals perpendicular to the plane of the molecule. > Chapter 7 4
Chapter 7 4 Orbital Description • Sigma bonds around C are sp2 hybridized. • Angles are approximately 120 degrees. • No nonbonding electrons. • Molecule is planar around the double bond. • Pi bond is formed by the sideways overlap of parallel p orbitals perpendicular to the plane of the molecule. =>
Bond Lengths and Angles 1.33 54 H 116.6° 121.7 ethylene ethane Hybrid orbitals have more s character. Pi overlap brings carbon atoms closer. Bond angle with pi orbital increases. >Angle C=C-His121.7° >Angle H-C-His116.6° => Chapter 7 5
Chapter 7 5 Bond Lengths and Angles • Hybrid orbitals have more s character. • Pi overlap brings carbon atoms closer. • Bond angle with pi orbital increases. ➢Angle C=C-H is 121.7 ➢Angle H-C-H is 116. 6 =>