Department of Chemistry, Emory University, Atlanta, Georgia 30322, USA.
J Phys Chem A. 2012 May 10;116(18):4466-72. doi: 10.1021/jp302247k. Epub 2012 Apr 27.
The mechanism and kinetics for the gas-phase hydrolysis of N(2)O(4) isomers have been investigated at the CCSD(T)/6-311++G(3df,2p)//B3LYP/6-311++G(3df,2p) level of theory in conjunction with statistical rate constant calculations. Calculated results show that the contribution from the commonly assumed redox reaction of sym-N(2)O(4) to the homogeneous gas-phase hydrolysis of NO(2) can be unequivocally ruled out due to the high barrier (37.6 kcal/mol) involved; instead, t-ONONO(2) directly formed by the association of 2NO(2), was found to play the key role in the hydrolysis process. The kinetics for the hydrolysis reaction, 2NO(2) + H(2)O ↔ HONO + HNO(3) (A) can be quatitatively interpreted by the two step mechanism: 2NO(2) → t-ONONO(2), t-ONONO(2) + H(2)O → HONO + HNO(3). The predicted total forward and reverse rate constants for reaction (A), k(tf) = 5.36 × 10(-50)T(3.95) exp(1825/T) cm(6) molecule(-2) s(-1) and k(tr) = 3.31 × 10(-19)T(2.478) exp(-3199/T) cm(3) molecule(-1) s(-1), respectively, in the temperature range 200-2500 K, are in good agreement with the available experimental data.
已在 CCSD(T)/6-311++G(3df,2p)//B3LYP/6-311++G(3df,2p) 理论水平上结合统计速率常数计算研究了 N(2)O(4)异构体的气相水解的机制和动力学。计算结果表明，由于涉及的高势垒（37.6 kcal/mol），通常假定的对称 N(2)O(4 的氧化还原反应对 NO(2)的均相气相水解的贡献可以明确排除；相反，由 2NO(2)缔合直接形成的 t-ONONO(2)被发现是水解过程中的关键作用。水解反应 2NO(2) + H(2)O ↔ HONO + HNO(3) (A)的动力学可以通过两步机制进行定量解释：2NO(2) → t-ONONO(2)，t-ONONO(2) + H(2)O → HONO + HNO(3)。预测反应（A）的总正向和反向速率常数，k(tf) = 5.36 × 10(-50)T(3.95) exp(1825/T) cm(6) molecule(-2) s(-1)和 k(tr) = 3.31 × 10(-19)T(2.478) exp(-3199/T) cm(3) molecule(-1) s(-1)，分别在 200-2500 K 的温度范围内，与可用的实验数据非常吻合。
