Reaction Equilibrium of the ω-Transamination of (S)-Phenylethylamine: Experiments and ePC-SAFT Modeling
Reaction Equilibrium of the ω-Transamination of (S)-Phenylethylamine: Experiments and ePC-SAFT Modeling
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DOI：
10.1021/acs.oprd.7b00078
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发表时间：
2017-07-01
影响因子：
3.4
通讯作者：
Sadowski, Gabriele
中科院分区：
文献类型：
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作者：
Voges, Matthias;Abu, Rohana;Sadowski, Gabriele
研究了水溶液中ω-转氨酶催化苯乙胺与环己酮反应生成苯乙酮和环己胺的热力学平衡。为此，在不同的反应条件下，实验研究了反应的平衡浓度。观察到温度（30 - 37 ℃）、pH（pH 7 - 9）以及初始反应物浓度（5 - 50）影响反应的平衡位置。mmol.kg反应平衡的位置适度地向产物侧移动，通过降低温度或降低pH值。相反，反应物的初始比率对平衡位置仅表现出边际影响。进一步的实验表明，增加初始反应物浓度显着移动的平衡位置的反应物侧。为了解释这些影响，计算了反应试剂的活度系数，并确定了反应的基于活度的热力学平衡常数Kth。为此，使用状态方程电解质PC-SAFT（ePC-SAFT）在其各自的实验平衡浓度下模拟反应剂的活度系数。平衡时反应试剂的浓度和它们各自的活度系数的组合提供了热力学上一致的平衡常数Kth。出乎意料的是，实验Km值偏离热力学平衡常数Kth高达四倍。所观察到的浓度依赖性的实验Kt值可以解释浓度对活度系数的影响。此外，发现这些活度系数强烈依赖于温度，这对于确定标准反应焓是重要的，在这项工作中发现标准反应焓为+7.7 +/-2.8 kJ·mol（-1）。使用如此确定的Kth和活性系数的反应剂（ePC-SAFT），反应的平衡浓度进行了预测，为不同的初始反应物浓度，这被发现是在良好的协议与实验行为。这些结果表明，反应试剂的活度系数对平衡位置的影响不可忽略，因此，对产物产率的影响不可忽略。实验和ePC-SAFT预测表明，平衡位置只能通过考虑活度系数来准确描述。
This work focuses on the thermodynamic equilibrium of the co-transaminase-catalyzed reaction of (S)-phenylethylamine with cyclohexanone to acetophenone and cyclohexylamine in aqueous solution. For this purpose, the equilibrium concentrations of the reaction were experimentally investigated under varying reaction conditions. It was observed that the temperature (30 and 37 degrees C), the pH (between pH 7 and pH 9), as well as the initial reactant concentrations (between 5 and 50 mmol.kg(-1)) influenced the equilibrium position of the reaction. The position of the reaction equilibrium was moderately shifted toward the product side by either decreasing temperature or decreasing pH. In contrast, the initial ratio of the reactants showed only a marginal influence on the equilibrium position. Further experiments showed that increasing the initial reactant concentrations significantly shifted the equilibrium position to the reactant side. In order to explain these effects, the activity coefficients of the reacting agents were calculated and the activity-based thermodynamic equilibrium constant Kth of the reaction was determined. For this purpose, the activity coefficients of the reacting agents were modeled at their respective experimental equilibrium concentrations using the equation of state electrolyte PC-SAFT (ePC-SAFT). The combination of the concentrations of the reacting agents at equilibrium and their respective activity coefficients provided the thermodynamically consistent equilibrium constant Kth. Unexpectedly, the experimental Km values deviated by a factor of up to four from the thermodynamic equilibrium constant Kth. The observed concentration dependency of the experimental Kt values could be explained by the influence of concentration on activity coefficients. Further, these activity coefficients were found to be strongly temperature dependent, which is important for the determination of standard enthalpy of reactions, which in this work was found to be +7.7 +/- 2.8 kJ.mol(-1). Using the so-determined Kth and activity coefficients of the reacting agents (ePC-SAFT), the equilibrium concentrations of the reaction were predicted for varying initial reactant concentrations, which were found to be in good agreement with the experimental behavior. These results showed a non-negligible influence of the activity coefficients of the reacting agents on the equilibrium position and, thus, on the product yield. Experiments and ePC-SAFT predictions showed that the equilibrium position can only be described accurately by taking activity coefficients into account.