Forryan Claire L, Klymenko Oleksiy V, Brennan Colin M, Compton Richard G
Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ, United Kingdom.
J Phys Chem B. 2005 Apr 28;109(16):8263-9. doi: 10.1021/jp0407573.
Understanding the mechanisms of solid-liquid systems is fundamental to the development and operation of processes for the production of agrochemicals and pharmaceuticals. The use of a strong inorganic base in an organic solvent, typically, potassium carbonate in dimethylformamide, is often used to facilitate the formation of a required anionic organic nucleophile. In this paper, the dissolution kinetics of potassium carbonate in dimethylformamide at elevated temperatures is studied in the presence of ultrasound, as revealed via monitoring of the deprotonation of 2-cyanophenol by dissolved K2CO3. Two independent experimental methods were employed; the loss of 2-cyanophenol was detected electrochemically at a platinum microdisk working electrode, and the formation of the 2-cyanophenolate anion was monitored via UV/visible spectroscopic analysis. The results were modeled by fitting the experimental data to a theoretical model for the surface-controlled dissolution of solid particles. The dissolution rate constant, k, for the dissolution of K2CO3 in DMF was found to have a value of (1.3 +/- 0.2) x 10(-7) mol cm(-2) s(-1) at 100 degrees C, and the activation energy for the dissolution was 44.2 +/- 0.4 kJ mol(-1) over the temperature range of 70-100 degrees C studied.
了解固液体系的机制是农用化学品和药品生产工艺开发与运行的基础。在有机溶剂中使用强碱，通常是在二甲基甲酰胺中使用碳酸钾，常用于促进所需阴离子有机亲核试剂的形成。本文研究了在超声作用下，碳酸钾在二甲基甲酰胺中高温下的溶解动力学，通过监测溶解的K2CO3对2-氰基苯酚的去质子化来揭示。采用了两种独立的实验方法；在铂微盘工作电极上电化学检测2-氰基苯酚的损失，并通过紫外/可见光谱分析监测2-氰基酚盐阴离子的形成。通过将实验数据拟合到固体颗粒表面控制溶解的理论模型对结果进行建模。发现在100℃时，K2CO3在DMF中的溶解速率常数k值为(1.3±0.2)×10(-7)mol cm(-2)s(-1)，在所研究的70-100℃温度范围内，溶解的活化能为44.2±0.4kJ mol(-1)。
