Direct dynamics calculations of multiple proton transfer through hydrogen-bonded wire and the role of micro-solvation in ClONO2 + H2O -> HNO3 + HOCl reactions

作者：Bang Youbin; Kim Seon Ho; Kim Yongho^*

来源：Theoretical Chemistry Accounts, 2017, 136(11): 132.

DOI：10.1007/s00214-017-2163-2

• Multiple proton transfer
• Micro-solvation
• C1ONO2 hydrolysis on ice
• Hydrogen-bonded water wire
• Variational transition state theory

The hydrolysis of C1ONO(2) on polar stratospheric ice has been considered as a major factor causing stratospheric ozone depletion. We have theoretically investigated the reaction dynamics of hydrolysis on ice surface and the role of micro- solvation. No theoretical studies have been performed for the micro-solvent effect of multiple proton transfer in the hydrolysis of C1ONO(2). Rate constants and tunneling coefficients were calculated using variational transition state theory including multidimensional tunneling. The dispersion corrected, spin-component scaled, double hybrid PBE functional with the P86 correlation that can reproduce the MP2/CBS +.CCSD(Q) result was used to generate potential energy surfaces. No more than three water molecules could form a cyclic hydrogen (H)-bonded chain to catalyze the reaction and the other is bound to the chain to act as a micro-solvent. The catalytic water reduced not only the barrier but also the tunneling effect significantly. The micro-solvent effect of lowering the barrier is smaller and depends on the position. The multiple proton transfer path through H-bonded chain, in some cases, varied with the position of micro-solvent, and consequently the H- bonded structure of HOCl- HNO3 cluster became completely different from the reactant and TS structures. The predicted rate constant was 0.671 at 193 K, and the Arrhenius activation energy was 8 kcal/mol. This rate constant was smaller by three orders of magnitude than that of ClONO2 + HCl on ice, which is consistent with the experimental observations that at low HCl concentration conditions - C1ONO(2) hydrolysis competes with C1ONO(2) + HCl reaction.

• 出版日期2017-10-25