Chemistry Tutorial: Aromaticity

Chemistry Tutorial: Aromaticity Based on a Chemistry 14C Honors Project Six carbons once formed in a ring, with sp 2 hybridization. The strain was relieved, and al six achieved electron delocalization ‘The stability, itself is dramatic,’ said a puzled o­chemist fanatic. ‘Al these factors at work just ad a new perk.’ And thus was proclaimed aromatic. Contents Section 1: Vocabulary Section 2: Determining Aromaticity Section 3: Conjugation and Aromaticity Section 4: Resonance and Aromaticity Section 5: Frequently Asked Questions Section

6: Common Errors Section 7: Readings and Sources Section 1: Vocabulary Exercise 1: (a) Define each term (b) Explain how it relates to aromaticity ‐ Aromaticity ‐ Conjugation ‐ Cyclic delocalization ‐ Resonance ‐ Pi bonds ‐ Partial Pi bonds ‐ Ring Strain Section 1: Vocabulary – Solutions Exercise 1: ‐ Aromaticity o A) Extra stability possessed by a molecule that meets specific criteria: pi bonds all must lie within a cyclic structure, loop of p orbitals, p orbitals must be planar and overlap, must follow Hückel’s Rule. o B) n/a ‐ Conjugation o A) The special stability provided by three or more adjacent, parallel, overlapping p orbitals. o B) Aromatic molecules, by default, have conjugation. As it takes a minimum of three, adjacent, overlapping p orbitals for planarity, aromaticity requires a minimum of this for conjugation. Aromaticity is like conjugation, but extra stable. ‐ Cyclic delocalization o A) Electron delocalization, or distribution of electron density, occurs as a result of overlapping p orbitals in a planar, cyclic structure. o B) A closed loop of overlapping p orbitals must be present for aromaticity to occur; therefore, cyclic delocalization occurs in aromatic molecules and is a contributor to the molecule’s extra...

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