Earth System Research Laboratory, Chemical Sciences Division, National Oceanic and Atmospheric Administration, 325 Broadway, Boulder, Colorado 80305-3328, USA.
J Phys Chem A. 2011 Sep 29;115(38):10539-49. doi: 10.1021/jp206195g. Epub 2011 Sep 1.
Rate coefficients, k, for the gas-phase reaction of the OH radical with (Z)-CF(3)CH═CHCF(3) (cis-1,1,1,4,4,4-hexafluoro-2-butene) were measured under pseudo-first-order conditions in OH using pulsed laser photolysis (PLP) to produce OH and laser-induced fluorescence (LIF) to detect it. Rate coefficients were measured over a range of temperatures (212-374 K) and bath gas pressures (20-200 Torr; He, N(2)) and found to be independent of pressure over this range of conditions. The rate coefficient has a non-Arrhenius behavior that is well-described by the expression k(1)(T) = (5.73 ± 0.60) × 10(-19) × T(2) × exp[(678 ± 10)/T] cm(3) molecule(-1) s(-1) where k(1)(296 K) was measured to be (4.91 ± 0.50) × 10(-13) cm(3) molecule(-1) s(-1) and the uncertainties are at the 2σ level and include estimated systematic errors. Rate coefficients for the analogous OD radical reaction were determined over a range of temperatures (262-374 K) at 100 Torr (He) to be k(2)(T) = (4.81 ± 0.20) × 10(-19) × T(2) × exp[(776 ± 15)/T], with k(2)(296 K) = (5.73 ± 0.50) × 10(-13) cm(3) molecule(-1) s(-1). OH radical rate coefficients were also measured at 296, 345, and 375 K using a relative rate technique and found to be in good agreement with the PLP-LIF results. A room-temperature rate coefficient for the O(3) + (Z)-CF(3)CH═CHCF(3) reaction was measured using an absolute method with O(3) in excess to be <6 × 10(-21) cm(3) molecule(-1) s(-1). The atmospheric lifetime of (Z)-CF(3)CH═CHCF(3) due to loss by OH reaction was estimated to be ~20 days. Infrared absorption spectra of (Z)-CF(3)CH═CHCF(3) measured in this work were used to determine a (Z)-CF(3)CH═CHCF(3) global warming potential (GWP) of ~9 for the 100 year time horizon. A comparison of the OH reactivity of (Z)-CF(3)CH═CHCF(3) with other unsaturated fluorinated compounds is presented.
用脉冲激光光解（PLP）产生 OH，并通过激光诱导荧光（LIF）检测，在 OH 自由基存在下，于 212-374 K 的温度范围内和 20-200 Torr（He、N2）的浴气压下，测定了（Z）-CF3CH═CHCF3（顺-1,1,1,4,4,4-六氟-2-丁烯）与 OH 自由基气相反应的速率系数，发现该速率系数在该条件范围内不随压力变化而变化。该速率系数具有非阿伦尼乌斯行为，用表达式 k1（T）=（5.73±0.60）×10-19×T2×exp[（678±10）/T]cm3分子-1s-1很好地描述，其中 k1（296 K）为（4.91±0.50）×10-13cm3分子-1s-1，不确定度在 2σ水平内，包括估计的系统误差。在 100 Torr（He）下，测定了温度范围为 262-374 K 时类似的 OD 自由基反应的速率系数为 k2（T）=（4.81±0.20）×10-19×T2×exp[（776±15）/T]，k2（296 K）=（5.73±0.50）×10-13cm3分子-1s-1。使用相对速率技术，在 296、345 和 375 K 下还测定了 OH 自由基的速率系数，与 PLP-LIF 结果吻合良好。用绝对方法测定了过量 O3存在下 O3+（Z）-CF3CH═CHCF3反应的室温速率系数，为 <6×10-21cm3分子-1s-1。由于 OH 反应造成（Z）-CF3CH═CHCF3的损耗，（Z）-CF3CH═CHCF3在大气中的寿命估计约为 20 天。本工作中测定的（Z）-CF3CH═CHCF3的红外吸收光谱用于确定其在 100 年时间范围内的全球变暖潜能（GWP）约为 9。还介绍了（Z）-CF3CH═CHCF3与其他不饱和氟化化合物的 OH 反应性比较。
