A novel long path photolysis cell—application to the reactivity of selected organic compounds toward the nitrate radical (NO<sub>3</sub>)
作者:Davy Rousse、Christian George
DOI:10.1039/b400175c
日期:——
Bimolecular rate coefficients for the reactions of the nitrate radical, NO3, with methanol, ethanol, acetaldehyde tert-butyl methyl ether, propionic acid, dimethylmalonate, dimethylsuccinate, dimethyl carbonate and diethylcarbonate in aqueous solutions have been measured using a novel experimental approach. This study was performed using laser flash photolysis (LFP) with a capillary made of Teflon AF2400 as a long path capillary photolysis cell. Taking benefit of this new material allowing a long optical path length for a very limited irradiated solution volume, new rate constants were established. All experiments were carried out at room temperature. Measured rate coefficients for the reaction of the NO3 radical with methanol, ethanol, acetaldehyde, dimethylcarbonate, diethylcarbonate, dimethylmalonate, dimethyl succinate, propionic acid and tert-butyl-methyl ether are (units are 105 Mâ1 sâ1): kNO3â+âethanolâ=â4.8â±â0.5, kNO3â+âethanolâ=â19â±â3, kNO3â+âacetaldehydeâ=â20â±â3, kNO3â+âdimethylcarbonateâ=â0.15â±â0.04, kNO3â+âdiethylcarbonateâ=â0.84â±â0.12, kNO3â+âdimethylmalonateâ=â0.26â±â0.07, kNO3â+âdimethylsuccinateâ=â0.34â±â0.02, kNO3â+âpropionic acidâ=â0.77â±â0.02, kNO3â+âtert-butyl-methyl etherâ=â3.9â±â1.3. The uncertainties in the above expressions are ±2Ï and represent precision only. The reported rate coefficients for the reactions of NO3 with methanol, ethanol and acetaldehyde agree well with currently recommended values. To date, there is no kinetic data reported in the literature for the NO3 radical reaction with dimethylcarbonate, diethylcarbonate, dimethylmalonate, dimethylsuccinate, propionic acid and tert-butyl-methyl ether. The reaction mechanism is briefly discussed as a function of bond energies
已使用一种新颖的实验方法测量了硝酸根自由基(NO3)与甲醇、乙醇、乙醛、叔丁基甲基醚、丙酸、二甲基马来酸盐、二甲基丁二酸盐、碳酸二甲酯和碳酸二乙酯在水溶液中的双分子反应速率系数。该研究采用激光闪光光解法(LFP),使用由特氟龙AF2400制成的毛细管作为长光程光解池。得益于这种新材料,它允许在非常有限的辐照溶液体积内实现较长的光学路径长度,建立了新的速率常数。所有实验均在室温下进行。NO3自由基与甲醇、乙醇、乙醛、二甲基碳酸酯、二乙基碳酸酯、二甲基马来酸盐、二甲基丁二酸盐、丙酸和叔丁基甲基醚反应的速率系数(单位为 10⁵ M⁻¹ s⁻¹)为:kNO3 + 乙醇 = 4.8 ± 0.5, kNO3 + 乙醇 = 19 ± 3, kNO3 + 乙醛 = 20 ± 3, kNO3 + 二甲基碳酸酯 = 0.15 ± 0.04, kNO3 + 二乙基碳酸酯 = 0.84 ± 0.12, kNO3 + 二甲基马来酸盐 = 0.26 ± 0.07, kNO3 + 二甲基丁二酸盐 = 0.34 ± 0.02, kNO3 + 丙酸 = 0.77 ± 0.02, kNO3 + 叔丁基甲基醚 = 3.9 ± 1.3。上述表达式中的不确定性为 ±2σ,仅表示精确度。NO3与甲醇、乙醇和乙醛反应的速率系数与目前推荐的值高度一致。到目前为止,文献中尚无NO3自由基与二甲基碳酸酯、二乙基碳酸酯、二甲基马来酸盐、二甲基丁二酸盐、丙酸和叔丁基甲基醚反应的动力学数据。反应机制将简要讨论作为键能的函数。