Constructing Molecular Orbitals Pi molecular orbitals are the sideways overlap of p orbitals. p orbitals have 2 lobes.Plus (+and minus (-)indicate the opposite phases of the wave function,not electrical charge. When lobes overlap constructively,(and +or-and -)a bonding MO is formed. When and-lobes overlap,waves cancel out and a node forms;antibonding MO.= Chaper 15 6
Chaper 15 6 Constructing Molecular Orbitals • Pi molecular orbitals are the sideways overlap of p orbitals. • p orbitals have 2 lobes. Plus (+) and minus (-) indicate the opposite phases of the wave function, not electrical charge. • When lobes overlap constructively, (+ and +, or - and -) a bonding MO is formed. • When + and - lobes overlap, waves cancel out and a node forms; antibonding MO. =>
Ethylene Pi MO's ·The combination of node two p orbitals must π* (antibonding)= give two molecular orbitals. destructive overlap energy of the isolated p orbitals on CI and C2 ● Constructive overlap is a bonding MO. energy (bonding)= 。Destructive overlap is an anti-bonding constructive overlap MO. => Copyright2005 Pearson Prentice Hall.Inc Chaper 15
Chaper 15 7 Ethylene Pi MO’s • The combination of two p orbitals must give two molecular orbitals. • Constructive overlap is a bonding MO. • Destructive overlap is an anti-bonding MO. =>
MO for 1,3-Butadiene ·Lowest energy, bonding bonding bonding ·All bonding interactions. ● Electrons are delocalized over four nuclei. Copyright2005 Peerson Prentce Hall,ine > Chaper 15 8
Chaper 15 8 1 MO for 1,3-Butadiene • Lowest energy. • All bonding interactions. • Electrons are delocalized over four nuclei. =>
2 MO for 1,3-Butadiene 。2 bonding bonding antibonding bonding interactions. 。1 antibonding interaction. ·A bonding MO. node Copyright2005 Pearson Prentice Hall.Inc. > Chaper 15 9
Chaper 15 9 2 MO for 1,3-Butadiene • 2 bonding interactions. • 1 antibonding interaction. • A bonding MO. =>
3*MO for 1,3-Butadiene antibonding antibonding ·Antibonding MO. bonding ·Empty at ground state. ·Two nodes. node node Copyright 2005 Pearson Prentice Hall.Inc Chaper 15 10
Chaper 15 10 3 * MO for 1,3-Butadiene • Antibonding MO. • Empty at ground state. • Two nodes. =>