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Unformatted text preview: Cyclic Systems Aromatic 4n + 2 electrons ( Hckels Rule ) Antiaromatic any other electron count Non Cyclic Systems Non Aromatic 6 electrons 4 electrons 6 electrons aromat c an aroma c nonaroma c aromatic antiaromatic nonaromatic Aromatic systems Cyclopentadiene is not stable for long at room temperature. It reacts with itself to form a dimer. 2 Diels Alder heat NaOH pKa = 16 n e = 6 FeCl 2 Fe(C 5 H 5 ) 2 ferrocene page 1011 in book Aromatic systems Cycloheptatrienyl cation n e = 6 n e = 6 Dibenzenechromium Cr(C H )(C H ) Cr(C 7 H 7 )(C 5 H 5 ) Cr(C 6 H 6 ) 2 Cycloheptatrienyl cation n e = 6 Stable cation also known as the tropylium ion BF 4- Antiaromatic system cylcooctatetraene non planar cylcooctatetraene n e = 8 non planar Aromatic system C H 2- n e = 10 C 8 H 8 e Heterocycles (cyclic molecules with at least one non carbon atom) N N All N N pyrimidine pyridine benzene N pyrazine n e = 6 sp 2 N N lone pai N H lone pair on Nitrogen pyridinium Heterocycles (cyclic molecules with at least one non carbon atom)...
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