Class Summary 11/01/04 Fun with Symmetry Answers

11/01 AROMATICITY

Four Accepted Criteria for Aromatic Systems

(a) Chemical behaviour: electrophilic substitution

(b) Structural effects: bond length equalization

(c) Energetics: enhanced stability

(d) Magnetic criteria: chemical shifts, magnetic anisotropy and diamagnetic susceptibility

Methods for assessing aromaticity

L Diamagnetic Susceptibility Exaltation (Schleyer)

Assess strain by fusing a 5-membered ring onto the system (W.C. Herndon approach)

PAPERS MENTIONED

Schleyer, P. v. R., Jiao, H. What is aromaticity? Pure & Appl. Chem. (1996), 68, 209-18.

Baldridge, K.K., Siegel, J.S. Stabilization of benzene versus oligoacetylenes: not another scale for aromaticity J. Phys. Org. Chem. (2004) 17, 740-742.

Herndon, W.C., unpublished results (personal communication to P.G. Wenthold).

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