CHEM267 Chapter Notes - Chapter 18: Annulene, Steric Effects, Antiaromaticity
5 Mar 2013
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Each c=c and c-c in benzene is not a double bond or single bond, but each is a 1. 5 bond . Cyclic compounds consisting of alternating single and double bonds do not have the same reactivity as benzene (aromatic stabilization) H ckel"s rule: there must be an odd number of electron pairs ( bonds) to be aromatic: must have 4n+2 electrons (2, 6, 10, 14, 18, etc. ) Simple method of drawing the energy levels of the mos of conjugated systems (frost circle): Aromatic compounds must satisfy the following 2 criteria: the compound must contain a ring comprised of continuously overlapping p orbitals, the number of electrons in the ring must be a h ckel number. Examples of nonaromatic compounds (don"t satisfy the 1st criterion): Antiaromatic = cyclic compounds that have 4n electrons. Annulenes = compounds consisting of a single ring containing a fully conjugated system.
