2.共轭体系能量降低，分子稳定性增加 C +2H2 +2H2 +2H2 70.5 kcal/mole -60.8 kcal/mole 54.1 kcal/mole- 70.5 kcal/mole - 54.1 kcal/mole - 60.8 kcal/mole 2. 共轭体系能量降低，分子稳定性增加