Brudnik Katarzyna, Wójcik-Pastuszka Dorota, Jodkowski Jerzy T, Leszczynski Jerzy
Department of Physical Chemistry, Wroclaw Medical University, Wroclaw, Poland.
J Mol Model. 2008 Dec;14(12):1159-72. doi: 10.1007/s00894-008-0358-0. Epub 2008 Oct 15.
Ab initio calculations at the G2 level were used in a theoretical analysis of the kinetics of unimolecular and water-accelerated decomposition of the halogenated alcohols CX(3)OH (X = F, Cl, and Br) into CX(2)O and HX. The calculations show that reactions of the unimolecular decomposition of CX(3)OH are of no importance under atmospheric conditions. A considerably lower energy pathway for the decomposition of CX(3)OH is accessible by homogenous reactions between CX(3)OH and water. It is shown that CX(3)OH + H(2)O reactions proceed via the formation of intermediate complexes. The mechanism of the reactions appears to be complex and consists of three consecutive elementary processes. The calculated values of the second-order rate constants are of 2.5 x 10(-21), 2.1 x 10(-19), and 1.2 x 10(-17) cm(3)molecule(-1)s(-1) at 300 K for CF(3)OH + H(2)O, CCl(3)OH + H(2)O, and CBr(3)OH + H(2)O, respectively. The theoretically derived atmospheric lifetimes of the CX(3)OH molecules indicate that the water-mediated decomposition reactions CX(3)OH + H(2)O may be the most efficient process of CF(3)OH, CCl(3)OH, and CBr(3)OH loss in the atmosphere.
在G2水平上进行的从头算计算被用于对卤代醇CX(3)OH（X = F、Cl和Br）单分子分解以及水加速分解为CX(2)O和HX的动力学进行理论分析。计算表明，CX(3)OH的单分子分解反应在大气条件下并不重要。通过CX(3)OH与水之间的均相反应，可以获得一条能量低得多的CX(3)OH分解途径。结果表明，CX(3)OH + H(2)O反应通过形成中间络合物进行。反应机理似乎很复杂，由三个连续的基元过程组成。在300 K时，CF(3)OH + H(2)O、CCl(3)OH + H(2)O和CBr(3)OH + H(2)O的二级速率常数计算值分别为2.5×10^(-21)、2.1×10^(-19)和1.2×10^(-17) cm³·分子⁻¹·s⁻¹。理论推导的CX(3)OH分子在大气中的寿命表明，水介导的分解反应CX(3)OH + H(2)O可能是CF(3)OH、CCl(3)OH和CBr(3)OH在大气中损失的最有效过程。
