The Foundations of Chemistry

Figure 9-11 Representations of the bonding in the benzene molecule, C 6 H 6. (a) Lewis
formulas of the two valence bond resonance structures. (b) The six porbitals of the benzene
ring, shown overlapping to form the (hypothetical) double bonds of the two resonance forms
of valence bond theory. (c) In the MO description the six electrons in the pi-bonded region
are delocalized,meaning they occupy an extended pi-bonding region above and below the
plane of the six C atoms.

9-6 Delocalization and the Shapes of Molecular Orbitals 367

HH

HH

HH

C C

C C

C C

HH

HH

HH

C C

C

C C

(a) Lewis formulas for valence bond resonance structures

HH

H

H H

H CC

CC

CC HH

H

H H

H CC

CC

CC

H

H

H

H

H

HC C

C

CC

(b) p-orbital overlap in valence bond resonance structures

(c)Delocalized MO representation

C