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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Theoretical Studies of Methyleneamino (CH_2N) Radical Reactions. 1. Rate Constants and Product Branching Rations for the CH_2N + N_2O Process by ab Initio Molecular Orbital/Statistical Theory Calculations.
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Theoretical Studies of Methyleneamino (CH_2N) Radical Reactions. 1. Rate Constants and Product Branching Rations for the CH_2N + N_2O Process by ab Initio Molecular Orbital/Statistical Theory Calculations.

机译：亚甲基氨基（CH_2N）自由基反应的理论研究。 1.通过从头算分子轨道/统计理论计算，得出CH_2N + N_2O过程的速率常数和产物支化比。

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High level molecular orbital calculations have been performed in the framework of the G2M method to study the kinetics and mechanism for the bimolecular reaction of CH_2N with N_2O, one of the key reactions considered in the RDX combustion modeling. Three different reaction channels have been identified for this reaction. The direct abstraction reaction, which occurs via transition state TS1 producing CH_2NO and N_2, has an activation barrier of 42.4 kcal/mol. A transition state theory calculation employing the predicted energies and molecular parameters gave rise to rate constant k(CH_2NO) = 2.84 * 10~(11) exp(-24900/T) cm~3/(molecules) in the temperature range 1000-3000 K. The CH_2N_N_2O reaction can also produce CH_2N_2 and NO either by the formation and decomposition of CH_2NN_2O intermediate LM1 via TS2 and TS3 or from the cyclic intermediate LM3 via transition state TS7, LM1 can also be formed from it isomer LM2 via TS5, which appears as an additional reaction path for the formation of CH_2N_2 and NO through the same TS3 transition state. LM3 can be formed by direct side-on addition of N_2O to CH_2N via a five-membered ring transition state (TS6) with a barrier of 37.3 kcal/mol. The RRKM theory predicted the total rate constant for the formation of CH_2N_2 by these three channels: k(CH_2N_2) = 9.93 * 10~(12) exp(-22000/T) in the same temperature range. The cyclic intermediate (LM3) can also undergo stepwise decomposition to form endothermic products CH_2O and N_3 via TS8, intermediate LM4 and TS9; the predicted maximum barrier of this path is 32.9 kcal/mol at TS8 with respect to the reactants. The results of RRKM calculations carried out at various temperature and pressure conditions indicate that the CH_2O+N_3 channel is least competitive, whereas the CH_2N_2_NO channel dominates the reaction up to 2500 K.
机译：已在G2M方法的框架内进行了高级分子轨道计算，以研究CH_2N与N_2O的双分子反应的动力学和机理，这是RDX燃烧建模中考虑的关键反应之一。已经为该反应确定了三个不同的反应通道。经由过渡态TS1产生CH_2NO和N_2的直接提取反应的活化势垒为42.4 kcal / mol。利用预测的能量和分子参数进行的过渡态理论计算得出了温度范围1000-3000时的速率常数k（CH_2NO）= 2.84 * 10〜（11）exp（-24900 / T）cm〜3 /（分子） K. CH_2N_N_2O反应还可以通过经由TS2和TS3形成和分解CH_2NN_2O中间体LM1或通过过渡态TS7由环状中间体LM3生成和分解CH_2N_2和NO，也可以通过TS5由异构体LM2形成LM1。作为通过相同TS3过渡态形成CH_2N_2和NO的附加反应路径。 LM3可以通过将N_2O通过五元环跃迁状态（TS6）直接侧向添加到CH_2N上而形成，势垒为37.3 kcal / mol。 RRKM理论预测了在相同温度范围内通过这三个通道形成CH_2N_2的总速率常数：k（CH_2N_2）= 9.93 * 10〜（12）exp（-22000 / T）。环状中间体（LM3）也可以通过TS8，中间体LM4和TS9逐步分解形成吸热产物CH_2O和N_3;相对于反应物，该路径在TS8的预测最大势垒为32.9 kcal / mol。在各种温度和压力条件下进行的RRKM计算结果表明，CH_2O + N_3通道的竞争性最低，而CH_2N_2_NO通道在2500 K以下主导反应。

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