尿酸质子转移反应的理论研究I——分子内质子转移研究

使用量子化学中的Hartree-Fock方法和密度泛函理论中的B3LYP方法，分别在3－21G^*和6－31G（d)水平上，计算了尿酸分子从三羰基异构体向三羟基异构体的转化。结果表明，转化过程经历了单羟基和双羟基异构体2种中间物和3种过渡态时的分子内质子转移（IPT），转移中的H原邻近的N，O和C原子形成了具有四元环结构的过渡态。随着IPT的进行，N－H键逐渐被削弱和断裂，O－H键则逐渐生成。3个反应的活化能分别为190.3kJ/mol,181.4kJ/mol和249.9kJ/mol(B3LYP/6-31G(d))。较高的活化能表明在室温下，无催化剂的IPT难以进行。

The theoretical study of the intramolecular proton transfer of uric acid molecule

Quantum chemistry theory of Hartree-Fock method at the 3-21G * basis set level and density functional theory with B3LYP method at the 6-31 G( d ) basis set level were employed to study the intramolecular proton transfer(IPT)process of uric acid molecule.In order to convert the three-carbonyl-group tautomer into the three-hydroxy-group one,the reaction undergoes two intermediates and three transition states.A four-membered cyclic substructure was formed in the transition state which involving transferring hydrogen atom and its neighboured nitrogen,oxygen and carbon atoms.The activation energies of the three reactions including scaled zero-point vibrational energies predicted by B3LYP/6-31G( d )are 190.3 kJ/mol,181 4 kJ/mol and 249 9 kJ/mol respectively and the last reaction is rate-determining step.