On the OH-initiated degradation of acrylic acid and selected methacrylates in the troposphere

M. B. BLANCO, G. R. LUQUE, R. A. TACCONE, S. I. LANE AND M. A. TERUEL

Orléans, France

Simposio; 19th International Symposium on Gas Kinetics (GK 2006; 2006

Gas Kinetic group-RSC Faraday Division

Acrylic acid (CH2=CHC(O)OH) and methacrylates (CH2=C(CH3)C(O)OR), where R is an alkyl group,  are widely used in the industry of polymers, paper coating, paint formulations , etc.  In addition they are produced naturally by marine algae and in the rumen fluid of sheep.1 The atmospheric fate of  unsaturated and oxygenated volatile organic compounds (VOCs) is mainly their reaction with OH radicals.2,3 As part of an ongoing program in our laboratory to study the atmospheric chemistry of oxygenated species, we report relative rate coefficients for the gas-phase reactions of OH radicals with acrylic acid (k1) and three unsaturated esters: methyl methacrylate (k2), ethyl methacrylate (k3) and n-butyl methacrylate (k4): OH + CH2=CHC(O)OH                                   Products,             (k1)                                                    OH + CH2=C(CH3)C(O)OCH3                                                       Products,  (k2)                             OH + CH2=C(CH3)C(O)OCH2CH3                                                Products,  (k3)                             OH + CH2=C(CH3)C(O)O CH2CH2CH2CH3                                   Products.                        (k4)    Kinetic experiments at room temperature and atmospheric pressure of air were performed using a relative-rate technique with GC-FID analysis. OH radicals were produced by the photolysis of CH3ONO in the presence of NO/O2.     Table 1: Reactant concentrations, kreactant/kref   and k reactant for the reaction of OH with acrylic acid, methyl ethacrylate, ethyl methacrylate and n-buthyl methacrylate at 298 K in 760 Torr of air. VOC [VOC]0 (ppm) Reference [Ref]0 (ppm) kreactant / kRef kreactant (cm3 molecule-1s-1) Acrylic acid 63 3-chloropropene 133 1.00 ± 0.06 (1.69 ± 0.17) x 10-11 64 Diethylether 114 1.34 ± 0.07 (1.51 ± 0.09) x 10-11 average (1.60 ± 0.17) x 10-11 83 3-chloropropene 83 2.47 ± 0.07 (4.17 ± 0.29) x 10-11 Methyl 142 3-chloropropene 126 2.48 ± 0.09 (4.19 ± 0.32) x 10-11 methacrylate 85 3-chloropropene 123 2.42 ± 0.08 (4.09 ± 0.30) x 10-11 average (4.15 ± 0.32) x 10-11 82 3-chloropropene 83 2.59 ± 0.10 (4.38 ± 0.35) x 10-11 Ethyl 139 3-chloropropene 146 2.63 ± 0.19 (4.44 ± 0.50) x 10-11 methacrylate 43 Diethyl ether 109 3.49 ± 0.15 (4.75