Branching ratios in reactions of OH radicals with methylamine, dimethylamine, and ethylamine.
Branching ratios in reactions of OH radicals with methylamine, dimethylamine, and ethylamine.
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DOI：
10.1021/es502398r
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发表时间：
2014-08
影响因子：
11.4
通讯作者：
L. Onel;M. Blitz;M. Dryden;L. Thonger;P. Seakins
中科院分区：
文献类型：
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作者：
L. Onel;M. Blitz;M. Dryden;L. Thonger;P. Seakins
用脉冲激光光解-激光诱导荧光技术测定了OH自由基与甲胺（MA）、二甲胺（DMA）和乙胺（EA）等伯、仲烷基胺反应的支链比。初始OH提取后形成的碳中心自由基，用氧滴定生成HO2和亚胺，然后与NO反应将HO2转化为OH，在毫秒时间尺度上产生双指数OH衰变痕迹。通过双指数曲线分析得到HO2产率，即αC-H位置提取的分支比r（αC-H）。该技术通过甲醇和乙醇的OH提取的已知分支比例进行了验证。在298 K下，r(αC-H，MA) = 0.76±0.08,r(αC-H，DMA) = 0.59±0.07,r(αC-H，EA) = 0.49±0.06，其中误差是2σ水平的统计误差和估计10%的系统误差的正交组合。OH与（CH3） 2nhh和CH3CH2NH2反应的分支比r（αC-H）与OD与（CH3）2ND （d-DMA）和CH3CH2ND2 （d-EA）反应的分支比r(αC-H,d-DMA) = 0.71±0.12,r(αC-H,d-EA) = 0.54±0.07。基于G4理论的势能面主方程分析（使用MESMER软件包）证明了实验结果不受稳定过氧自由基形成的影响，并用于估计大气压力产率。在1atm N2条件下，O2与α碳中心自由基反应生成亚胺的支化比分别为r(CH2NH2) = 0.79±0.15,r(CH2NHCH3) = 0.72±0.19,r(CH3CHNH2) = 0.50±0.18。简要讨论了这项工作对亚硝胺和硝胺的潜在形成的影响。
The branching ratios for the reaction of the OH radical with the primary and secondary alkylamines: methylamine (MA), dimethylamine (DMA), and ethylamine (EA), have been determined using the technique of pulsed laser photolysis-laser-induced fluorescence. Titration of the carbon-centered radical, formed following the initial OH abstraction, with oxygen to give HO2 and an imine, followed by conversion of HO2 to OH by reaction with NO, resulted in biexponential OH decay traces on a millisecond time scale. Analysis of the biexponential curves gave the HO2 yield, which equaled the branching ratio for abstraction at αC-H position, r(αC-H). The technique was validated by reproducing known branching ratios for OH abstraction for methanol and ethanol. For the amines studied in this work (all at 298 K): r(αC-H,MA) = 0.76 ± 0.08, r(αC-H,DMA) = 0.59 ± 0.07, and r(αC-H,EA) = 0.49 ± 0.06 where the errors are a combination in quadrature of statistical errors at the 2σ level and an estimated 10% systematic error. The branching ratios r(αC-H) for OH reacting with (CH3)2NH and CH3CH2NH2 are in agreement with those obtained for the OD reaction with (CH3)2ND (d-DMA) and CH3CH2ND2 (d-EA): r(αC-H,d-DMA) = 0.71 ± 0.12 and r(αC-H,d-EA) = 0.54 ± 0.07. A master equation analysis (using the MESMER package) based on potential energy surfaces from G4 theory was used to demonstrate that the experimental determinations are unaffected by formation of stabilized peroxy radicals and to estimate atmospheric pressure yields. The branching ratio for imine formation through the reaction of O2 with α carbon-centered radicals at 1 atm of N2 are estimated as r(CH2NH2) = 0.79 ± 0.15, r(CH2NHCH3) = 0.72 ± 0.19, and r(CH3CHNH2) = 0.50 ± 0.18. The implications of this work on the potential formation of nitrosamines and nitramines are briefly discussed.