Atmospheric oxidation mechanism of methyl pivalate, (CH3)(3)CC(O)OCH3

Flash photolysis-resonance fluorescence techniques were used to measure the rate constant for the reaction of OH radicals with methyl pivalate, (CH3)( 3)CC(O)OCH3 over the temperature range 250-370 K. The rate constant exhibit ed a weak temperature dependence, increasing at both low and high temperatu re from a minimum value of approximately 1.2 x 10(-12) cm(3) molecule(-1) s (-1) near room temperature. The UV absorption spectrum of methyl pivalate w as measured between 160 and, 500 nm at room temperature. Smog chamber/FTIR techniques were used to study the Cl atom and OH radical initiated oxidatio n of (CH3)3CC(O)OCH3 in the presence of NOx in 700 Torr of N-2/O-2 diluent at 296 K. Relative rate techniques were used to measure k(Cl+(CH3)(3)CC(O)O CH3) = (4.1 +/- 0.5) x 10(-11), k(Cl+(CH3)(3)CC(O)OCH2Cl) = (1.8 +/- 0.3) x 10(-11), and k(Cl+(CH3)(3)CC(O)OC(O)OH) = (1.7 +/- 0.2) x 10(-11) cm(3) mo lecule(-1) s(-1). The reaction of Cl atoms with (CH3)(3)CC(O)OCH3 was found to proceed (11 +/- 3) % via H-abstraction at the -OCH3 site. The Cl atom i nitiated oxidation of (CH3)(3)CC(O)OCH3 in the presence of 15-600 Torr Of O -2 and 10-30 mTorr of NOx in 700 Torr total pressure of N-2 diluent at 296 K gives HCHO, CO, acetone, CO2, and CH3OC(O)O2NO2 products. OH radical init iated oxidation of (CH3)(3)CC(O)OCH3 in air produces acetone in a yield of 51 +/- 6%. Environmental chamber experiments were performed to quantify the effect of methyl pivalate on ozone formation under simulated atmospheric c onditions. An expression, representing the atmospheric oxidation mechanism of methyl pivalate in computer models of atmospheric chemistry is recommend ed.