H MOs for Cyclobutadiene 8 antibonding bonding bonding antibonding antibonding 88 Chapter 16
Chapter 16 11 MO’s for Cyclobutadiene =>
H Energy diagram for Cyclobutadiene 4 Following Hund's rule. two electrons are in separate nonbonding 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. =>
H 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 yclobutadiene 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. =>