Departamento de Química Física, Facultad de Ciencias Químicas, Universidad de Castilla La Mancha, Ciudad Real, Spain.
Environ Sci Pollut Res Int. 2010 Mar;17(3):539-46. doi: 10.1007/s11356-009-0220-7. Epub 2009 Jul 25.
BACKGROUND, AIM, AND SCOPE: Acrylate and methacrylate esters are alpha,beta-unsaturated esters that contain vinyl groups directly attached to the carbonyl carbon (CH(2)=CHCOO- and CH(2)=CCH(3)COO-, respectively) and are widely used in the polymer plastic and resin production. Rate coefficients for Cl reactions for most of the unsaturated esters have not been previously determined, and a good understanding is needed of all the atmospheric oxidation processes of these compounds in order to determine lifetimes in the atmosphere and to evaluate the impact of these reactions on the formation of photo-oxidants and therefore on health and environment.
The relative rate technique has been used to obtain rate coefficients for the reactions between the Cl atom and a series of unsaturated esters. The experiments have been carried out in a static Teflon reactor at room temperature and atmospheric pressure (N(2) as bath gas) using gas chromatography with flame ionization detection as detection system.
The following rate coefficients are obtained (in cubic meter per molecule per second): methyl acrylate + Cl = 1.71 +/- 0.13 x 10(-10); methyl methacrylate + Cl = 2.30 +/- 0.18 x 10(-10); ethyl acrylate + Cl = 1.82 +/- 0.13 x 10(-10); ethyl methacrylate + Cl = 2.71 +/- 0.21 x 10(-10); butyl acrylate + Cl = 2.94 +/- 0.23 x 10(-10); butyl methacrylate + Cl = 3.83 +/- 0.30 x 10(-10); methyl 3-methyl acrylate + Cl = 2.21 +/- 0.17 x 10(-10); and methyl 3,3-dimethyl acrylate + Cl = 3.58 +/- 0.28 x 10(-10).
Rate coefficients calculated for Cl reactions are around one order of magnitude higher than OH ones. The effect in the reactivity of increased substitution at the carbon-carbon double bond is analyzed and also the effect of the identity of the alkyl group R in the -C(O)OR. Atmospheric lifetimes of the compounds against the attack by the major oxidants are estimated and the atmospheric implications are discussed.
The dominant atmospheric loss process for acrylate esters is clearly their daytime reaction with the hydroxyl radical. However, in coastal areas and in the marine boundary layer and in some industrial zones, Cl-atom-initiated degradation of the unsaturated esters considered here can be a significant if not dominant homogeneous loss process.
Product analysis should be necessary in order to evaluate the real environmental impact of these reactions. OH and ozone reactions of most of the considered compounds have already been studied and products determined, but kinetic and products information for NO(3) radical reactions is especially scarce.
背景、目的和范围：丙烯酸盐和甲基丙烯酸盐是α,β-不饱和酯，其中包含直接连接在羰基碳上的乙烯基（CH(2)=CHCOO- 和 CH(2)=CCH(3)COO-，分别），并广泛用于聚合物塑料和树脂生产。大多数不饱和酯的 Cl 反应速率系数尚未被确定，为了确定在大气中的寿命并评估这些反应对光氧化剂形成的影响，因此对健康和环境的影响，需要了解这些化合物的所有大气氧化过程。
相对速率技术已用于获得一系列不饱和酯与 Cl 原子之间的反应速率系数。实验在室温下和大气压力下（N(2) 作为浴气体）在静态铁氟龙反应器中进行，使用气相色谱法结合火焰电离检测作为检测系统。
得到以下速率系数（以立方米每分子每秒计）：甲基丙烯酸盐+Cl=1.71+/-0.13x10(-10)；甲基甲基丙烯酸盐+Cl=2.30+/-0.18x10(-10)；乙基丙烯酸盐+Cl=1.82+/-0.13x10(-10)；乙基甲基丙烯酸盐+Cl=2.71+/-0.21x10(-10)；正丁烯酸酯+Cl=2.94+/-0.23x10(-10)；正丁基甲基丙烯酸盐+Cl=3.83+/-0.30x10(-10)；甲基 3-甲基丙烯酸盐+Cl=2.21+/-0.17x10(-10)；和甲基 3,3-二甲基丙烯酸盐+Cl=3.58+/-0.28x10(-10)。
Cl 反应的速率系数计算值比 OH 反应的速率系数计算值高一个数量级左右。分析了增加碳-碳双键上取代基的反应性的影响，以及 -C(O)OR 中 R 烷基的身份的影响。估计了化合物对主要氧化剂攻击的大气寿命，并讨论了大气影响。
对于丙烯酸盐酯来说，其主要的大气损失过程显然是其与羟基自由基的日间反应。然而，在沿海地区和海洋边界层以及一些工业区，这里考虑的不饱和酯的 Cl 原子引发的降解可以是一个重要的，如果不是主要的均相损失过程。
为了评估这些反应的真实环境影响，有必要进行产品分析。大多数考虑的化合物的 OH 和臭氧反应已经被研究过并且确定了产物，但对 NO(3) 自由基反应的动力学和产物信息尤其缺乏。
