羟自由基与水杨酸反应机理的初探

探讨羟自由基与水杨酸的反应动力学过程。水杨酸与Fenton反应产生的的羟自由基反应,采用紫外-可见分光光度法（UV）和质谱法（MS）,考察反应物的浓度、反应时间、反应温度、溶剂pH值等对反应产物的浓度以及反应速率的影响。水杨酸与.OH反应生成的紫色产物在波长530nm处有最大UV吸收峰,但仅于pH=4.51的缓冲溶液和水中有吸收峰;且该产物的吸光度值,随着反应物浓度的增加而增加;随反应时间的延长而减少;随着反应温度的升高而减少。反应速率t=5s达到最大值,其后随着反应时间的延长而逐渐降低,1min时达到平衡。通过MS分析,可得到质荷比（m/Z）=153,248,249,288,289,304,328,329,344,345的离子峰。推测羟自由基与水杨酸反应的中间产物是紫色的大分子自由基,而最终产物为二羟基苯甲酸,该反应可能是加成反应和聚合反应同时进行。

Investigation on Reaction Kinetics of Salicylic Acid and Hydroxyl Radical

The reaction dynamics of hydroxyl radical and salicylic acid was explored. Hydroxyl radical was produced by fenton reaction. The impact dynamics factors of this reaction were studied by ultraviolet and visible spectrophotometry （UV） and mass spectrometry （MS）,such as the reaction of concentration,reaction time,temperature,the pH of solvents. The purple intermediate product was generated by the reaction of salicylic acid and ·OH.The UV λmax=530nm was measured just in distilled water and pH=4.51 buffer solution.The concentration of the intermediate product was increased with increased concentration of reaction, Reduced with extension of reaction time, Reduced with rose temperature. In addition, the reaction rate reached maxium at t = 5s, then gradually reduced , it reached balance at t = lmin. Mass spectra of ion m/Z = 153,248,249,288,289,304,328, 329,344,345 was generated. Based on the reaction kinetics study of hydroxyl radical and salicylic acid, it estimated that the purple intermediate products were free radicals of weight molecular, the reaction could be addition and polymerization reaction.