Distance-Dependent Diffusion-Controlled Reaction of •NO and O2•− at Chemical Equilibrium with ONOO−

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• 作者：Horacio Botti ; Matas N. Mller ; Daniel Steinmann ; Thomas Nauser ; Willem H. Koppenol ; Ana Denicola ; Rafael Radi
• 刊名：Journal of Physical Chemistry B
• 出版年：2010
• 出版时间：December 16, 2010
• 年：2010
• 卷：114
• 期：49
• 页码：16584-16593
• 全文大小：279K
• 年卷期：v.114,no.49(December 16, 2010)
• ISSN：1520-5207

文摘

The fast reaction of ^•NO and O₂^•− to give ONOO⁻ has been extensively studied at irreversible conditions, but the reasons for the wide variations in observed forward rate constants (3.8 ≤ k_f ≤ 20 × 10⁹ M⁻¹ s⁻¹) remain unexplained. We characterized the diffusion-dependent aqueous (pH > 12) chemical equilibrium of the form ^•NO + O₂^•− = ONOO⁻ with respect to its dependence on temperature, viscosity, and [ONOO⁻]_eq by determining [ONOO⁻]_eq and [^•NO]_eq. The equilibrium forward reaction rate constant (k_f^eq) has negative activation energy, in contrast to that found under irreversible conditions. In contradiction to the law of mass action, we demonstrate that the equilibrium constant depends on ONOO⁻ concentration. Therefore, a wide range of k_f^eq values could be derived (7.5−21 × 10⁹ M⁻¹ s⁻¹). Of general interest, the variations in k_f can thus be explained by its dependence on the distance between ONOO⁻ particles (sites of generation of ^•NO and O₂^•−).