N_2H_4分子取代基效应的量子化学研究

Quantum Chemistry Study on the Substituent Effect of N_2H_4

计算了甲基(—CH_3)和羟基(—OH)对N_2H_4的取代基效应.引入甲基后,N_2H_4的N—N键长变长,电荷密度变小.羟基的引入,使得N—N键长变短,其中1,1,2,2-四羟基N_2H_4的N—N键长显著变化.通过NBO计算,N—N键的键级随着取代基个数的增加逐渐减小,超共轭作用在决定构型相对稳定性方面起了重要作用.引入取代基后,N原子的孤对电子与N—C(N—O)键之间发生相互作用,使得整个分子的超共轭作用增强.随着取代基数目的增多,分子的总能量和生成热均降低,取代基数目与分子相对稳定性之间具有较好的相关性.

Studies on substituent effects of the methyl（ —CH3） and hydroxyl（ —OH） group on hydrazine were performed. For derivatives substituted methyl,the N—N bond length of hydrazine was increased,and charge dengsity was lessened. For derivatives substituted hydroxyl,the N—N bond length of hydrazine was shortened. By NBO（ nature bond orbit）,the bond order of N—N bond was decreased with the increase of the number of the substituent. The hyperconjugation played a important role in the relative stability of isomers. The hyperconjugation from the lone pair electrons of atom N to the N—C（ N—O） bond was increased by the introduction of substituent. The total energy and formation heat were decreased with the addition of substituents. A good correlation was found between the numher of substituent and molecular relative stability.