Macdonald R Glen
Chemistry Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439, USA.
Phys Chem Chem Phys. 2007 Aug 21;9(31):4301-14. doi: 10.1039/b701900a. Epub 2007 May 1.
The rate constant and product branching ratios for the reaction of the cyanato radical, NCO(X (2)Pi), with the ethyl radical, C(2)H(5)(X (2)A''), have been measured over the pressure range of 0.28 to 0.59 kPa and at a temperature of 293 +/- 2 K. The total rate constant, k(1), increased with pressure, P(kPa), described by k(1) = (1.25 +/- 0.16) x 10(-10) + (4.22 +/- 0.35) x 10(-10)P cm(3) molecule(-1) s(-1). Three product channels were observed that were not pressure dependent: (1a) HNCO + C(2)H(4), k(1a) = (1.1 +/- 0.16) x 10(-10), (1b) HONC + C(2)H(4), k(1b) = (2.9 +/- 1.3) x 10(-11), (1c) HCN + C(2)H(4)O, k(1c) = (8.7 +/- 1.5) x 10(-13), with units cm(3) molecule(-1) s(-1) and uncertainties of one-standard deviation in the scatter of the data. The pressure dependence was attributed to a forth channel, (1d), forming recombination products C(2)H(5)NCO and/or C(2)H(5)OCN, with pressure dependence: (1d) k(1d) = (0.090 +/- 1.3) x 10(-11) + (3.91 +/- 0.27) x 10(-10)P cm(3) molecule(-1) s(-1). The radicals were generated by the 248 nm photolysis of ClNCO in an excess of C(2)H(6). Quantitative infrared time-resolved absorption spectrophotometry was used to follow the temporal dependence of the reactants and the appearance of the products. Five species were monitored, HCl, NCO, HCN, HNCO, and C(2)H(4), providing a detailed picture of the chemistry occurring in the system. Other rate constants were also measured: ClNCO + C(2)H(5), k(10) = (2.3 +/- 1.2) x 10(-13) , NCO + C(2)H(6), k(2) = (1.6 +/- 0.11) x 10(-14), NCO + C(4)H(10), k(4) = (5.3 +/- 0.51) x 10(-13), with units cm(3) molecule(-1) s(-1) and uncertainties of one-standard deviation in the scatter of the data.
在0.28至0.59 kPa的压力范围内以及293±2 K的温度下，测量了异氰酸根自由基NCO(X²Π)与乙基自由基C₂H₅(X²A″)反应的速率常数和产物分支比。总速率常数k₁随压力P(kPa)增加，其关系为k₁ = (1.25±0.16)×10⁻¹⁰ + (4.22±0.35)×10⁻¹⁰P cm³·分子⁻¹·s⁻¹。观察到三个与压力无关的产物通道：(1a) HNCO + C₂H₄，k₁a = (1.1±0.16)×10⁻¹⁰；(1b) HONC + C₂H₄，k₁b = (2.9±1.3)×10⁻¹¹；(1c) HCN + C₂H₄O，k₁c = (8.7±1.5)×10⁻¹³，单位为cm³·分子⁻¹·s⁻¹，数据散射的不确定性为一个标准偏差。压力依赖性归因于第四个通道(1d)，形成重组产物C₂H₅NCO和/或C₂H₅OCN，其压力依赖性为：(1d) k₁d = (0.090±1.3)×10⁻¹¹ + (3.91±0.27)×10⁻¹⁰P cm³·分子⁻¹·s⁻¹。自由基通过在过量C₂H₆中对ClNCO进行248 nm光解产生。采用定量红外时间分辨吸收分光光度法跟踪反应物的时间依赖性和产物的出现。监测了五种物质，HCl、NCO、HCN、HNCO和C₂H₄，从而详细了解了系统中发生的化学反应。还测量了其他速率常数：ClNCO + C₂H₅，k₁₀ = (2.3±1.2)×10⁻¹³；NCO + C₂H₆，k₂ = (1.6±0.11)×10⁻¹⁴；NCO + C₄H₁₀，k₄ = (5.3±0.51)×10⁻¹³，单位为cm³·分子⁻¹·s⁻¹，数据散射的不确定性为一个标准偏差。
