Page 156 - Pharm.Org.Chem I 05-PC101 (1)
P. 156
Electronic structure of benzene
• Benzene has symmetrical planar hexagonal structure, with sp2
hybridized carbons, and bond angles of 120o .
• The six identical Carbon-carbon bond lengths are 1.39 A (C-C: 1.54,
C=C: 1.34 A). The six C-H bond lengths are identical 1.09 A.
• Benzene hydrogen atoms are electronically equivalent(sp2-s) .
• the p orbital of any one carbon overlaps equally well the p orbitals of
both carbon atoms to which it is bonded, and the result is:
2 doughnut-shaped electron clouds, one lying above and the
other lying below the plane of the atoms.
2025-026 Dr. Marwa El-Wakil The six π electrons are
said to be delocalized.
9
• Aromatic compounds are characterized by:
✓ Cyclic
✓ Planar
✓ Highly unsaturated
✓ Conjugated
✓ Resonance-stabilized
✓ Obeys Hückel’s Rule
2025-026 Dr. Marwa El-Wakil 10
154
