Cycloheptatrienyl Cation Planar... 6πelectrons, therefore aromatic H OH H H (pH<3) H H+,H,O H H H H H H Tropylium Ion tropylium ion,six pi electrons Copyright 2010 Pearson Prentice Hall,Inc
Tropylium Ion
◆ 薁 l0元-electrons The two major (neutral)resonance forms for azulene... Aromatic “cyclopentadiene “cycloheptatriene Zwitterionic anion-like” cation-like” 两性离子的 ...and the very stable Zwiterionic form
◆ 薁 + _ Zwitterionic 两性离子的
8 薁 5 8 >350℃ 异构化 5 3 4
薁 1 2 3 5 4 6 7 8 1 2 3 5 4 6 7 8 > 350 ℃ 异构化
6日 s0 8e 6④ 6Φ Contrast the electron density map of azulene with that of napthalene,which has no significant Zwitterionic component
+ _
并环戊二烯负离子 Account for the differences in reactivity between pentalene (an unknown compound)and the well-known pentalene dianion: 2 K very unstable stable 8 a-electrons; 10π-electrons; not aromatic aromatic
并环戊二烯负离子