Departamento de Química Física, Facultad de Ciencias Químicas, Universidad de Castilla La Mancha, Avda Camilo José Cela 10, 13071 Ciudad Real, Spain.
Environ Sci Pollut Res Int. 2011 Jul;18(6):940-8. doi: 10.1007/s11356-011-0448-x. Epub 2011 Feb 1.
BACKGROUND, AIM, AND SCOPE: Methacrylates are α, β-unsaturated esters that are widely used in the polymer plastics and resins production. Kinetic information of NO(3) radical reactions is especially scarce and a good understanding of all the atmospheric oxidation processes of these compounds is necessary in order to determine lifetimes in the atmosphere and to evaluate the impact of these reactions on the formation of ozone and other photooxidants.
The experiments have been carried out using the relative technique in a static Teflon reactor at room temperature and atmospheric pressure (N(2) as bath gas) using gas chromatography (GC)-flame ionization detection (FID) as detection system. Products were analyzed using solid phase microextraction (SPME)-GC-mass spectrometry (MS) technique and Fourier transform infrared spectroscopy (FTIR) using air as bath gas.
The following rate coefficients were obtained (in cm(3) molecule(-1) s(-1)): methyl methacrylate + NO(3) = (3.55 ± 0.62) × 10(-15), ethyl methacrylate + NO(3) = (5.42 ± 1.90) × 10(-15), butyl methacrylate + NO(3) = (7.87 ± 3.86) × 10(-15). Methylpyruvate, ethylpyruvate, and butylpyruvate/butanol were identified as main degradation products respectively in the GC-MS analysis. Nitrates compounds were also identified in the FTIR study.
The reactivity increases with the substitution and with the chain of the alkyl group in -C(O)OR. An electrophilic addition mechanism is proposed as dominant degradation process. Estimations of the atmospheric lifetimes clearly indicate that the dominant atmospheric loss process for methacrylate esters is their daytime reaction with the hydroxyl radical. NO(3) and ozone are the main oxidants at night time.
A detailed products analysis including quantification could elucidate the mechanism for butanol generation for butyl methacrylate reaction.
背景、目的和范围：甲基丙烯酸盐是广泛应用于聚合物塑料和树脂生产的α，β-不饱和酯。关于 NO(3)自由基反应的动力学信息尤其稀缺，为了确定在大气中的半衰期并评估这些反应对臭氧和其他光氧化剂形成的影响，需要充分了解这些化合物的所有大气氧化过程。
实验是在室温及大气压力下（以氮气为浴气），于聚四氟乙烯静态反应器中利用相对方法，并使用气相色谱（GC）-火焰离子化检测（FID）作为检测系统进行的。产物使用固相微萃取（SPME）-GC-质谱（MS）技术和空气浴的傅立叶变换红外光谱（FTIR）进行分析。
得到了以下速率系数（单位为 cm(3)分子(-1) s(-1)）：甲基丙烯酸甲酯+NO(3)=（3.55±0.62）×10(-15)，乙基丙烯酸甲酯+NO(3)=（5.42±1.90）×10(-15)，丁基丙烯酸甲酯+NO(3)=（7.87±3.86）×10(-15)。在 GC-MS 分析中，分别鉴定出了主要降解产物甲基丙酮酸、乙基丙酮酸和丁基丙酮酸/丁醇。在 FTIR 研究中还鉴定出了硝酸盐化合物。
取代基和烷基链的增加使反应性增强。提出了亲电加成机理作为主要的降解过程。大气寿命的估算清楚地表明，对于甲基丙烯酸盐酯类，其主要的大气损耗过程是它们与羟基自由基在白天的反应。夜间，硝酸盐和臭氧是主要氧化剂。
对包括定量分析在内的详细产物分析可以阐明丁基丙烯酸甲酯与丁醇生成的反应机制。
