On the OH-initiated degradation of methacrylates in the troposphere: gas-phase kinetics and formation of pyruvates

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

CHEMICAL PHYSICS LETTERS

Elsevier

Año: 2006 vol. 429 p. 389 - 394

0009-2614

Rate coefficients for the gas-phase reactions of OH radicals with methyl methacrylate (k1), ethyl methacrylate (k2) and n-butyl methacrylate(k3) were determined to be k1= (4.15 ± 0.32 ) x 10-11  cm3 molecule-1 s-1, k2= (4.58 ± 0.59 ) x 10-11  cm3 molecule-1 s-1and k3= (7.08 ± 0.75 ) x 10-11 cm3 molecule-1 s-1, respectively. We performed kinetic experiments at room temperature and atmospheric pressure of air in the presence of NO using the relative-rate technique with GC-FID analysis. This is the first kinetic study of the reactions of OH radicals with ethyl methacrylate and n-butyl methacrylate. Additionally, product identification under atmospheric conditions was performed for the first time for these unsaturated esters by the GC-MS technique. Methyl-pyruvate, ethyl-pyruvate and n-butyl pyruvate were observed as  degradation products in accordance with the addition of OH to the less substituted carbon atom of the double bond, followed by decomposition of the 1-2-hydroxyalcoxy radicals formed. Kinetic data were used to estimate the atmospheric lifetimes of the esters studied.