Departament de Química Física, Universitat de València, 46100 Burjassot, Spain.
J Am Chem Soc. 2012 Jun 27;134(25):10509-14. doi: 10.1021/ja3026455. Epub 2012 Jun 19.
Decarboxylation of mandelylthiamin in aqueous solution is analyzed by means of quantum mechanics/molecular mechanics simulations including solvent effects. The free energy profile for the decarboxylation reaction was traced, assuming equilibrium solvation, while reaction trajectories allowed us to incorporate nonequilibrium effects due to the solvent degrees of freedom as well as to evaluate the rate of the diffusion process in competition with the backward reaction. Our calculations that reproduce the experimental rate constant show that decarboxylation takes place with a non-negligible free energy barrier for the backward reaction and that diffusion of carbon dioxide is very fast compared to the chemical step. According to these findings catalysts would not act by preventing the backward reaction.
在包括溶剂效应的量子力学/分子力学模拟的帮助下，对水溶液中马黛因硫胺的脱羧反应进行了分析。追踪了脱羧反应的自由能曲线，假设平衡溶剂化，而反应轨迹使我们能够将由于溶剂自由度引起的非平衡效应以及评估扩散过程与逆向反应竞争的速率纳入其中。我们的计算再现了实验速率常数，表明脱羧反应对于逆向反应具有不可忽略的自由能障碍，并且与化学步骤相比，二氧化碳的扩散非常快。根据这些发现，催化剂不会通过阻止逆向反应起作用。
