用从头算对丙烯和甲苯2个超共轭体系进行计算,结果表明甲基上氢原子参与超共轭时,其碳氢键键长增大,氢上集居数减少,丙烯、甲苯的甲基旋转势垒为7.61及0.096 kJ/mol.超共轭基作用相当于一带有孤对电子参与共轭之杂原子,超共轭体系不同构型稳定性可用M=sum from i=1 to 3(sinθ_i[sin(θ_i-α)+sinα])来表征。 The ab initio calculations of two hyperconjugated systems of propylene and toluene showed that when the hydrogen atom on the methyl group participates in the hyperconjugation, the carbon-hydrogen bond length increases and the number of hydrogen bonds decreases. The basal rotary barrier is 7.61 and 0.096 kJ / mol, respectively. The superconjugation effect is equivalent to a heteroatom with a lone pair of electrons participating in the conjugation. The stability of the different conformations of the hyperconjugated system is given by M = sum from i = 1 to 3 (sinθ_i [sin (θ_i-α) + sinα]).