臭氧与二乙胺和三乙胺气相反应的速率常数

利用自制的烟雾箱系统研究了臭氧与二乙胺和三乙胺的气相反应动力学. 实验过程中保证二乙胺和三乙胺浓度远远大于臭氧浓度, 使得实验在准一级条件下进行. 加入环己烷以消除实验过程中可能产生的OH自由基对反应的影响. 在(298±1) K和1.01×105 Pa条件下, 测得臭氧与二乙胺和三乙胺反应的绝对速率常数值分别为(1.33±0.15)×10^-17和(8.20±1.01)×10^-17 cm³·molecule^-1·s^-1. 与文献中已有的其它胺类的臭氧反应数据比较后发现, 臭氧与胺的反应可以用亲电反应机制来解释. 另外, 通过对比发现, 臭氧与三取代的烷基胺类的反应速率要远远大于其与二取代的烷基胺类的反应速率. 这在一定程度上可有助于解释外场观测到的气溶胶相中二烷基胺盐较多的事实. 利用测得的速率常数和大气中臭氧浓度, 还估算了二乙胺和三乙胺与臭氧反应的大气寿命. 结果显示, 与臭氧的反应是二乙胺和三乙胺在大气中的一种重要的消除途径, 尤其是在污染严重地区.

Rate Constants for the Gas Phase Reactions of Ozone with Diethylamine and Triethylamine

Kinetics of the reactions of ozone with diethylamine (DEA) and triethylamine (TEA) were investigated in a self-made Teflon chamber. Experiments were conducted under pseudo-first-order decay conditions using excess DEAand TEA. Cyclohexane was added to the reactor to quench OHradicals. At (298±1)Kand 1.01×105 Pa, the measured absolute rate constants were (1.33±0.15)×10^-17 cm³·molecule^-1·s^-1 for DEA and (8.20±1.01)×10^-17 cm³·molecule^-1·s^-1 for TEA. Comparing our results with data for the reactions of analogous amines with ozone, we propose that the amines react with ozone probably through an electrophilic reaction mechanism. In addition, the reactions of trialkylamines with ozone are all much faster than those of dialkylamines with ozone, which may explain the intriguing finding in several field studies where higher concentrations of dialkylammoniumwere detected in aerosol samples. The atmospheric lifetimes of DEA and TEA were also estimated based on the measured rate constants and the ambient tropospheric concentration of ozone, which indicates that the reaction with ozone is an important loss pathway for these amines in the atmosphere, especially in polluted areas.