CHAPTER 16 - CHAPTER 16 What makes something Aromatic? 1....

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CHAPTER 16 What makes something Aromatic? 1. Cyclic 2. Planar-flat with p -orbitals lined up 3. Continuous π –orbital pathway . Includes cations and anions ( sp 2 hybridized) 4. Must be especially stable (must show 36 kcal/mol) 5. Must follow Hückel’s Rule . Cyclic, fully conjugated, planar molecules with 4 n + 2 pi electrons ( n = any integer including zero). . 2 6 10 14 Highest Occupied Molecular Orbitals (HOMO’s) H The highest-energy molecular orbitals that contain electrons Antiaromatic H Meets criteria 1-3, but pi delocalization increases energy . Compounds with half-filled HOMO’s Non-Aromatic H Doesn’t fit rules 1-3 Heterocyclic Aromatic Compounds Two pi -electron Systems ( Aromatic) π Cyclopropenyl cation Four pi -electron Systems (Antiaromatic) π Cyclobutadiene . Cyclopropenyl anion . Cyclopentadienyl cation Six pi -electron Systems ( Aromatic) π Benzene . Cyclopentadienyl anion . Cycloheptatrienyl cation . Pyridine . Pyrrole . Furan Eight pi -electron Systems (Antiaromatic if planar)
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This note was uploaded on 05/04/2008 for the course CHM 228 taught by Professor Rosen during the Spring '08 term at Rhode Island.

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CHAPTER 16 - CHAPTER 16 What makes something Aromatic? 1....

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