Sec 2 Aromaticity and Reactivity 芳香性判别(Hiickel rules) 闭合的共轭体系（环状π电子流） .4n+2 Cyclopentadienyl Anion Planar... 6πelectrons, therefore aromatic Sec 2 Aromaticity and Reactivity ❖芳香性判别(Hückel rules) ◼闭合的共轭体系(环状电子流) ◼4n+2