Absolute Rate Coefficient of the Gas-Phase Reaction between Hydroxyl Radical (OH) and Hydroxyacetone: Investigating the Effects of Temperature and Pressure

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• 作者：Ngoc Duy Vu ; Victor Khamaganov ; Vinh Son Nguyen ; Shaun A. Carl ; Jozef Peeters
• 刊名：Journal of Physical Chemistry A
• 出版年：2013
• 出版时间：November 27, 2013
• 年：2013
• 卷：117
• 期：47
• 页码：12208-12215
• 全文大小：338K
• 年卷期：v.117,no.47(November 27, 2013)
• ISSN：1520-5215

文摘

The rate coefficient (k₁) of the reaction between hydroxyl radical and hydroxyacetone, which remained so far controversial, was determined over the temperature range 290鈥?00 K using pulsed-laser photolysis coupled to pulsed-laser induced fluorescence (PLP-PLIF). Hydroxyl radical was generated by pulsed photolysis of H₂O₂ at 248 nm. The results show that at a pressure of 50 Torr He, the rate coefficient obeys a negative temperature dependence k₁(T) = (1.77 卤 0.19) 脳 10^鈥?2 exp((353 卤 36)/T) cm³ molecule^鈥? s^鈥? for temperatures between 290 and 380 K, in good agreement with the results of Dillon et al. ( Phys. Chem. Chem. Phys. 2006, 8, 236) at 60 Torr He. However, always at 50 Torr He but for the higher temperature range 410鈥?00 K, a positive temperature dependence was found: k₁(T) = (1.14 卤 0.25) 脳 10^鈥?1 exp(鈭?378 卤 102)/T) cm³ molecule^鈥? s^鈥?, close to the expression obtained by Baasandorj et al. ( J. Phys. Chem. A 2009, 113, 10495) for pressures of 2 and 5 Torr He but at lower temperatures, 280鈥?60 K, where their k₁(T) values are well below these of Dillon et al. and of this work. Moreover, the rate coefficient k₁(301 K) determined as a function of pressure, from 10 to 70 Torr He, shows a pronounced decrease once the pressure is below 40 Torr He, thus explaining the disparity between the higher-pressure data of Dillon et al. and the lower-pressure results of Baasandorj et al. The pressure dependence of k₁ and of its temperature-dependence below 400 K is rationalized by the reaction proceeding via a hydrogen-bonded prereactive complex (PRC) and a submerged transition state, such that at high pressures collisionally thermalized PRCs contribute additional reactive flux over and through the submerged barrier. The high-pressure rate coefficient data both of Dillon et al. and of this work over the combined range 230鈥?00 K can be represented by the theory-based expression k₁(T) = 5.3 脳 10^鈥?0 脳 T^2.6 exp(1100/T) cm³ molecule^鈥? s^鈥?.