Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, PR China.
Phys Chem Chem Phys. 2010 May 14;12(18):4800-8. doi: 10.1039/b919330h. Epub 2010 Mar 16.
Ketoprofen is an important photosensitive drug molecule that has received much attention for the study of its photochemistry in different solvents. In this paper, nanosecond time-resolved resonance Raman spectroscopy was utilized to investigate the photochemistry of ketoprofen in aqueous solutions with varying water concentrations. The rate constants and reaction mechanism of ketoprofen are strongly dependent on the concentration of the solvent. In neat acetonitrile and solvents with low concentrations of water (like water-acetonitrile <or= 1 : 1, v/v), ketoprofen exhibits mostly benzophenone-like photochemistry to generate a triplet state which in turn produces a ketyl radical-like species by a hydrogen abstraction reaction. However, in solvents with very high concentrations of water (such as water-acetonitrile >or= 9 : 1, v/v), the triplet state ketoprofen is observed first and then undergoes a prompt decarboxylation process to form a triplet protonated biradical carbanion species. For solvents with moderate higher water concentrations (such as between 50% and 90% water by volume), the hydrogen abstraction and decarboxylation processes are two competitive pathways with different rate constants. The triplet state of ketoprofen will simultaneously produce a ketyl radical species and a triplet protonated biradical carbanion species with the amount of each species dependent on the water concentration.
酮洛芬是一种重要的光敏感药物分子，因其在不同溶剂中的光化学反应而备受关注。在本文中，我们利用纳秒时间分辨共振拉曼光谱研究了不同水浓度下水溶液中酮洛芬的光化学反应。酮洛芬的速率常数和反应机制强烈依赖于溶剂的浓度。在纯乙腈和低水浓度的溶剂（如水-乙腈<或=1:1，体积比）中，酮洛芬主要表现出类似于二苯甲酮的光化学反应，生成三重态，进而通过氢提取反应产生酮基自由基样物质。然而，在水浓度非常高的溶剂（如水-乙腈>或=9:1，体积比）中，首先观察到三重态酮洛芬，然后经历快速脱羧过程，形成三重态质子化双自由基碳阴离子物质。对于具有中等较高水浓度的溶剂（如体积比为 50%至 90%的水），氢提取和脱羧过程是两条具有不同速率常数的竞争途径。酮洛芬的三重态将同时产生酮基自由基物质和三重态质子化双自由基碳阴离子物质，每种物质的数量取决于水的浓度。
