DFT at the B3LYP/6-311++G(d,p) level of theory was performed to geometrically, thermodynamically, and kinetically investigate the tautomerism process of 2-aminobenzothiazole (ABT) with n water molecules ( n = 1–3) and without water in the gas phase and in different solvents with a gradual increase in their dielectric constants. The geometries of the envisaged tautomers were optimized in the gas phase and in solution with the polarized continuum model (PCM). Equilibrium and rate constants for the forward and reverse intra-/intermolecular isolated and water-assisted tautomerism reactions were also calculated. The results suggest that the activation energy of the transition state of direct proton transfer in the isolated reaction is very high and that the rate constant is very slow (~ 10 −24 s), reflecting that the reaction is thermodynamically unfavored, whereas the barrier differences between the transition states of the tautomers decrease gradually as the number of water molecules increases from one to three. Moreover, the rate constants of the proposed reactions are ~ 10 23 –10 25 faster than those of the isolated reaction, and the water-assisted tautomerism paths can be performed quickly, especially with the assistance of two molecules of water.

中文翻译：

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气相和不同溶剂中 2-氨基苯并噻唑 (ABT) 中分子内和分子间质子转移过程的 DFT 研究

在 B3LYP/6-311++G(d,p) 理论水平上进行 DFT 以几何、热力学和动力学研究 2-氨基苯并噻唑 (ABT) 与 n 个水分子 (n = 1–3) 的互变异构过程并且在气相中和在介电常数逐渐增加的不同溶剂中没有水。设想的互变异构体的几何形状在气相和溶液中使用极化连续模型 (PCM) 进行了优化。还计算了正向和反向分子内/间分离和水辅助互变异构反应的平衡和速率常数。结果表明，孤立反应中直接质子转移过渡态的活化能非常高，速率常数非常慢（~10 -24 s），反映该反应在热力学上是不利的，而随着水分子数从 1 增加到 3，互变异构体过渡态之间的势垒差异逐渐减小。此外，所提出的反应的速率常数比孤立反应的速率常数快~10 23 –10 25 ，并且水辅助的互变异构路径可以快速进行，特别是在两个水分子的帮助下。