2-巯基吡啶质子迁移过程的理论研究

采用密度泛函理论,在B3LYP/6-311G**基组水平上,计算并考察了2-巯基吡啶分子硫醇式结构和硫酮式结构进行结构互变质子迁移过程中的4种可能途径:(a)分子内质子迁移,(b)水助质子迁移,(c)同种二聚体双质子迁移和(d)异种二聚体间双质子迁移.计算结果表明,途经c所需要的活化能最小(9.73 kJ.mol-1,逆反应则为55.28 kJ.mol-1),而过程a所需要的活化能最大(106.02 kJ.mol-1),途径b和d的活化能居中间(分别为32.05和15.91 kJ.mol-1).研究还表明,氢键在降低反应活化能方面起着重要的作用.

Theoretical Study on the Proton Transfer of 2-Thiopyridine

The processes of the proton transfer between two tautomers,thione and the thiol of 2-thiopyridine were investigated by using density functional theory at B3LYP/6-311G~(**) leve1.The four possible reaction pathways:(a) intramolecular proton transfer;(b) water assisted intermolecular transfer;(c) isomerization by double proton transfer in the dimer and(d) intermolecular proton transfer via the complex formed by thione tautomer and the thiol one of 2-thiopyridine,were investigated.The calculated results showed that the processes in(b),(c) and(d) have lower activation energies than that of(a) because of the formation of hydrogen bonded complexes in(b),(c) and(d).The activation energies corrected by scaled zero point vibrational energies for the four reaction processes calculated at the B3LYP/6 311G~(**)level are 106.02,32.05,9.73 and 15.91 kJ mol~(-1),respectively.It is likely that the hydrogen bonds formed in the complexes play an important role in the proton transfer process.