Organic Chemistry,7th Edition L.G.Wade,Jr. Chapter 7 Structure and Synthesis of Alkenes Copyright 2010 Pearson Education,Inc
Chapter 7 Copyright © 2010 Pearson Education, Inc. Organic Chemistry, 7th Edition L. G. Wade, Jr. Structure and Synthesis of Alkenes
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 2
Chapter 7 2 Introduction • Alkenes are hydrocarbon with carbon-carbon double bonds. • Alkenes are also called olefins, meaning “oilforming gas”. • The functional group of alkenes is the carboncarbon double bond, which is reactive
Sigma Bonds of Ethylene 2 p sp H H sigma bonding orbitals of ethylene Copyright2010 Pearson Prentice Hall,Inc. Chapter 7 3
Chapter 7 3 Sigma Bonds of Ethylene
Orbital Description ● Sigma bonds around the double-bonded carbon are sp2 hybridized. ·Angles are approximately12o°and the molecular geometry is trigonal planar. Unhybridized p orbitals with one electron will overlap forming the double bond (pi bond). Chapter 7 4
Chapter 7 4 Orbital Description • Sigma bonds around the double-bonded carbon are sp2 hybridized. • Angles are approximately 120ºand the molecular geometry is trigonal planar. • Unhybridized p orbitals with one electron will overlap forming the double bond (pi bond)
Bond Lengths and Angles 116.6° 121.7° H ethylene ethane Copyright2010 Pearson Prentice Hall,Inc. sp2 hybrid orbitals have more s character than the sp3 hybrid orbitals. Pi overlap brings carbon atoms closer shortening the C-C bond from 1.54 A in alkanes down to 1.33 A in alkenes. Chapter 7 5
Chapter 7 5 Bond Lengths and Angles • sp2 hybrid orbitals have more s character than the sp3 hybrid orbitals. • Pi overlap brings carbon atoms closer shortening the C—C bond from 1.54 Å in alkanes down to 1.33 Å in alkenes