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首页> 外文期刊>Physical chemistry chemical physics: PCCP >Toward elimination of discrepancies between theory and experiment: The gas-phase reaction of N2O5 with H2O
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Toward elimination of discrepancies between theory and experiment: The gas-phase reaction of N2O5 with H2O

机译：消除理论与实验之间的差异：N2O5与H2O的气相反应

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摘要

New reaction mechanisms are presented and the corresponding reaction rate constants are calculated for the homogeneous gas-phase reaction N2O5 + nH(2)O <-> 2HNO(3) + (n - 1)H2O with n = 1,2,3 using ab initio methods and canonical variational transition state theory including tunneling corrections. The reaction barriers for the new mechanisms are 21.1 kcal mol(-1) for n = 1, 18.9 kcal mol(-1) for n = 2 and for the two mechanisms with three water molecules 14.2 and 19.2 kcal mol(-1). Using the new reaction mechanism the rate constant for N2O5 hydrolysis with n = 1 is k(1) = 5.2 x 10(-25) cm(-3) molecule(-1) s(-1) at 298 K, which is in much better agreement with the experimental value being only two orders of magnitude smaller, compared to the old mechanism which is ten orders of magnitude smaller than the experimental value. Also the rate constant for the third order process second order with respect to [H2O] is in better agreement with experiment compared with the old mechanism (seven compared to approximately twelve orders of magnitude). For possible future confirmation of the new reaction mechanisms we determined kinetic isotope effects for the reactions and obtained KIEs of 1.55 and 1.09 for n = 1 and n = 2 water molecules, respectively, compared to 1.11 and 1.44 for the old mechanisms. [References: 66]
机译：提出了新的反应机理，并针对n = 1,2,3的均相气相反应N2O5 + nH（2）O <-> 2HNO（3）+（n-1）H2O计算了相应的反应速率常数从头算方法和规范的变分过渡状态理论，包括隧道校正。新机制的反应壁垒是n = 1时为21.1 kcal mol（-1），n = 2时为18.9 kcal mol（-1）以及两个具有三个水分子14.2和19.2 kcal mol（-1）的机理。使用新的反应机理，n = 1的N2O5水解速率常数为298 K时的k（1）= 5.2 x 10（-25）cm（-3）分子（-1）s（-1）。与旧机制相比，实验值仅小两个数量级，而实验值仅小两个数量级，因此更好地达成了一致。与旧机制相比，三阶过程[H2O]相对于[H2O]的速率常数与实验更好地吻合（与大约十二个数量级相比为七）。为了进一步确认新的反应机理，我们确定了反应的动力学同位素效应，对于n = 1和n = 2的水分子，KIE分别为1.55和1.09，而旧机理的KIE分别为1.11和1.44。 [参考：66]

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