MO's for Cyclobutadiene node y" antibonding bonding bonding antibonding antibonding > Chapter 16 11
Chapter 16 11 MO’s for Cyclobutadiene =>
Energy Diagram for Cyclobutadiene 米 ·Following Hund's rule,two electrons are in separate nonbonding元2 orbitals. line ·This diradical would be very reactive. => Chapter 16 12
Chapter 16 12 Energy Diagram for Cyclobutadiene • Following Hund’s rule, two electrons are in separate orbitals. • This diradical would be very reactive. =>
Polygon Rule The energy diagram for an annulene has the same shape as the cyclic compound with one vertex at the bottom. nonbonding line benzene cyclobutadiene cyclooctatetraene => Chapter 16 13
Chapter 16 13 Polygon Rule The energy diagram for an annulene has the same shape as the cyclic compound with one vertex at the bottom. =>
Aromatic Requirements Structure must be cyclic with conjugated pi bonds. Each atom in the ring must have an unhybridized p orbital. The p orbitals must overlap continuously around the ring.(Usually planar structure) 。 Compound is more stable than its open- chain counterpart. Chapter 16
Chapter 16 14 Aromatic Requirements • Structure must be cyclic with conjugated pi bonds. • Each atom in the ring must have an unhybridized p orbital. • The p orbitals must overlap continuously around the ring. (Usually planar structure) • Compound is more stable than its openchain counterpart. =>