摘要
用密度泛函理论方法,在B3LYP/6-31G水平上研究了巴比妥酸的醇式和酮式结构的分子内质子迁移异构化反应,对反应势能面的研究发现,该化合物可能存在6种中间体和12种过渡态,对反应物、产物和过渡态进行了几何构型优化,在同一水平下计算了单点能量,并用频率振动模式和内稟坐标(IRC)确证了过渡态的存在,反应的活化能最小为107.50kJ·mol-1,最大为330.84kJ·mol-1。在GIAO-HF/6-31G//B3LYP/6-31G水平对反应物、产物,中间体和过渡态的非相关性化学位移(NICS)进行了计算,利用NICS值对反应过程中芳香性进行分析,发现如果分子中的C5与C6存在双键或者形成过渡态的四员环状结构,分子就有不同程度的芳香性,如果有C6上的羟基氢迁移到C5上,C5-C6以单键相结合,则分子就没有芳香性。
Density functional theory （DFT） of quantum chemistry method was used to investigate the proton transfer reaction of barbituric acid by studying the potential energy surface of the isomerization. Geometries were optimized at DFT levels by employing B3LPY/6-31G＊＊. It was found that there were 6 monomer isomers and 12 transition states in possible reaction pathways. The stationary points on each one of the reaction channels are confirmed by the IRC tracing and image frequency. The lowest and largest reaction activation energy were 107.50 kJ·mol^-1 and 330.84 kJ·mol^-1. The nucleus-independent chemical shifts of the reactant （NICS）, product, 6 monomer isomers and 12 transition states of barbituric acid have been calculated at the GIAO-HF/6-31G＊//B3LYP/6-31G＊＊ level, the NICS values were used to assess the aromaticity of the reactant, product, 6 monomer isomers and 12 transition states of barbituric.
出处
《合成化学》
CAS
CSCD
2007年第1期55-59,84,共6页
Chinese Journal of Synthetic Chemistry
关键词
巴比妥酸
密度泛函理论
互变异构化
过渡态
芳香性
barbituric acid
density functional theory
tautomerization
transition state
aromaticity
