Homogeneous Catalysis Laboratory, Department of Chemistry, The University of Burdwan, Golapbag, Burdwan, 713 104 WB, India.
Spectrochim Acta A Mol Biomol Spectrosc. 2013 May 15;109:55-67. doi: 10.1016/j.saa.2013.02.019. Epub 2013 Feb 21.
The kinetics of oxidation of benzaldehyde by chromic acid in aqueous and aqueous surfactant (sodium dodecyl sulfate, SDS, alkyl phenyl polyethylene glycol, Triton X-100 and N-cetylpyridinium chloride, CPC) media have been investigated in the presence of promoter at 303 K. The pseudo-first-order rate constants (kobs) were determined from a logarithmic plot of absorbance as a function time. The rate constants were found to increase with introduction of heteroaromatic nitrogen base promoters such as Picolinic acid (PA), 2,2'-bipyridine (bipy) and 1,10-phenanthroline (phen). The product benzoic acid has been characterized by conventional melting point experiment, NMR, HRMS and FTIR spectral analysis. The mechanism of both unpromoted and promoted reaction path has been proposed for the reaction. In presence of the anionic surfactant SDS, cationic surfactant CPC and neutral surfactant TX-100 the reaction can undergo simultaneously in both aqueous and micellar phase with an enhanced rate of oxidation in the micellar phase. Both SDS and TX-100 produce normal micellar effect whereas CPC produce reverse micellar effect in the presence of benzaldehyde. The observed net enhancement of rate effects has been explained by considering the hydrophobic and electrostatic interaction between the surfactants and reactants. SDS and bipy combination is the suitable one for benzaldehyde oxidation.
在 303K 下，在促进剂存在下，研究了在水相和水相表面活性剂（十二烷基硫酸钠（SDS）、烷基苯聚乙二醇、吐温 X-100 和氯化 N-十六烷基吡啶，CPC）介质中，铬酸氧化苯甲醛的动力学。通过吸光度随时间的对数图确定了伪一级速率常数（kobs）。发现随着杂芳族氮碱基促进剂如吡啶甲酸（PA）、2,2'-联吡啶（bipy）和 1,10-菲咯啉（phen）的引入，速率常数增加。产物苯甲酸已通过常规熔点实验、NMR、高分辨质谱（HRMS）和傅里叶变换红外光谱（FTIR）分析进行了表征。提出了未促进和促进反应途径的反应机理。在阴离子表面活性剂 SDS、阳离子表面活性剂 CPC 和中性表面活性剂 TX-100 的存在下，反应可以在水相和胶束相同时进行，胶束相中的氧化速率得到提高。SDS 和 TX-100 均产生正常胶束效应，而 CPC 在存在苯甲醛时产生反胶束效应。通过考虑表面活性剂和反应物之间的疏水和静电相互作用，解释了观察到的速率增强的净效应。SDS 和 bipy 的组合是苯甲醛氧化的合适组合。
