School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, UK.
School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff, CF10 3AT, UK.
Angew Chem Int Ed Engl. 2017 Jul 24;56(31):9044-9047. doi: 10.1002/anie.201703700. Epub 2017 Jun 29.
The rate coefficients for gas-phase reaction of trifluoroacetic acid (TFA) with two Criegee intermediates, formaldehyde oxide and acetone oxide, decrease with increasing temperature in the range 240-340 K. The rate coefficients k(CH OO + CF COOH)=(3.4±0.3)×10 cm s and k((CH ) COO + CF COOH)=(6.1±0.2)×10 cm s at 294 K exceed estimates for collision-limited values, suggesting rate enhancement by capture mechanisms because of the large permanent dipole moments of the two reactants. The observed temperature dependence is attributed to competitive stabilization of a pre-reactive complex. Fits to a model incorporating this complex formation give k [cm s ]=(3.8±2.6)×10 T exp((1620±180)/T) + 2.5×10 and k [cm s ]=(4.9±4.1)×10 T exp((1620±230)/T) + 5.2×10 for the CH OO + CF COOH and (CH ) COO + CF COOH reactions, respectively. The consequences are explored for removal of TFA from the atmosphere by reaction with biogenic Criegee intermediates.
三氟乙酸（TFA）与两种 Criegee 中间体甲醛氧化物和丙酮氧化物在气相中的反应速率系数随温度在 240-340K 范围内升高而降低。在 294K 时，速率系数 k(CH OO + CF COOH)=(3.4±0.3)×10 cm s 和 k((CH ) COO + CF COOH)=(6.1±0.2)×10 cm s 超过了碰撞限制值的估计值，表明由于两种反应物的永久偶极矩较大，捕获机制会增强反应速率。观察到的温度依赖性归因于预反应络合物的竞争稳定化。将该络合物形成纳入模型的拟合给出 k [cm s ]=(3.8±2.6)×10 T exp((1620±180)/T) + 2.5×10 和 k [cm s ]=(4.9±4.1)×10 T exp((1620±230)/T) + 5.2×10 ，分别用于 CH OO + CF COOH 和 (CH ) COO + CF COOH 反应。探讨了与生物源 Criegee 中间体反应从大气中去除 TFA 的后果。
