Antiñolo María, Jiménez Elena, González Sergio, Albaladejo José
Departamento de Química Física, Facultad de Ciencias y Tecnologías Químicas, Universidad de Castilla-La Mancha, Avda. Camilo José Cela s/n, 13071 Ciudad Real, Spain.
J Phys Chem A. 2014 Jan 9;118(1):178-86. doi: 10.1021/jp410283v. Epub 2013 Dec 17.
The relative importance in the atmosphere of UV photolysis of perfluoropropionaldehyde, CF3CF2CHO, and reaction with hydroxyl (OH) radicals has been investigated in this work. First, the forbidden n → π* transition of the carbonyl chromophore was characterized between 230 and 380 nm as a function of temperature (269–298 K) and UV absorption cross sections, σλ, were determined in those ranges. In addition, IR absorption cross sections were determined between 4000 and 500 cm–1. Pulsed laser photolysis (PLP) of CF3CF2CHO coupled to Fourier transform infrared (FTIR) was employed to determine the overall photolysis quantum yield, Φλ, at 308 nm and 298 K. Φλ=308 nm was pressure dependent, ranging from (0.94 ± 0.14) at 75 Torr to (0.30 ± 0.01) at 760 Torr. This dependence is characterized by the Stern–Volmer parameters Φ0λ=308 nm = (1.19 ± 0.34) and KSV = (1.22 ± 0.52) × 10(–19) cm3 molecule–1. End products of the photodissociation of CF3CF2CHO were measured and quantified by FTIR spectroscopy. Furthermore, the rate coefficients for the OH + CF3CF2CHO reaction, k1, were determined as a function of temperature (T = 263–358 K) by PLP-LIF. At room temperature the rate coefficient is k1(T = 298 K) = (5.57 ± 0.07) × 10(–13) cm3 molecule–1 s–1, whereas the temperature dependence is described by k1(T) = (2.56 ± 0.32) × 10(–12) exp{−(458 ± 36)/T} cm3 molecule–1 s–1. On the basis of our results, photolysis of CF3CF2CHO in the actinic region could be an important removal process for CF3CF2CHO in the atmosphere. The formation of the primary products in the UV photolysis of CF3CF2CHO is also discussed.
本研究考察了全氟丙醛（CF3CF2CHO）在大气中的紫外光解以及与羟基（OH）自由基反应的相对重要性。首先，对羰基发色团在230至380 nm之间的禁阻n→π*跃迁进行了表征，作为温度（269 - 298 K）的函数，并在这些范围内测定了紫外吸收截面σλ。此外，还测定了4000至500 cm–1之间的红外吸收截面。采用CF3CF2CHO的脉冲激光光解（PLP）与傅里叶变换红外（FTIR）联用，测定了308 nm和298 K下的总光解量子产率Φλ。Φλ=308 nm与压力有关，在75 Torr时为(0.94 ± 0.14)，在760 Torr时为(0.30 ± 0.01)。这种依赖性由Stern–Volmer参数表征，Φ0λ=308 nm = (1.19 ± 0.34)，KSV = (1.22 ± 0.52) × 10(–19) cm3分子–1。CF3CF2CHO光解离的终产物通过FTIR光谱进行了测量和定量。此外，通过PLP-LIF测定了OH + CF3CF2CHO反应的速率系数k1作为温度（T = 263 - 358 K）的函数。在室温下，速率系数为k1(T = 298 K) = (5.57 ± 0.07) × 10(–13) cm3分子–1 s–1，而温度依赖性由k1(T) = (2.56 ± 0.32) × 10(–12) exp{−(458 ± 36)/T} cm3分子–1 s–1描述。基于我们的结果，CF3CF2CHO在光化区域的光解可能是大气中CF3CF2CHO的一个重要去除过程。还讨论了CF3CF2CHO紫外光解中初级产物的形成。
