8 8©8 se 8C ǒ白 se 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 very unstable stable 8 a-electrons; 10π-electrons; not aromatic aromatic
并环戊二烯负离子
环辛五烯 Would you predict cyclodecapentaene to be an aromatic compound? 空间障碍 Cyclodecapentaene
空间障碍 环辛五烯
Steric repulsion between the opposing hydrogens forces the x system out of planarity,therefore the molecule is not aromatie
◆大环芳香体系 具有交替的单双键的单环多烯烃，通称为轮烯(annulenes) 共平面性或接近平面性，平面扭转又大于0.1nm 芳香性 轮内氢原子间没有或很少有空间排斥作用 π电子数目符合4n+2规则 H [10]轮烯 [14]轮烯 [18轮烯
◆ 大环芳香体系 具有交替的单双键的单环多烯烃，通称为轮烯（annulenes） 芳香性 共平面性或接近平面性，平面扭转又大于0.1nm 轮内氢原子间没有或很少有空间排斥作用 π电子数目符合4n+2规则 [18]轮烯 ［10］轮烯 ［14］轮烯