ATMOSPHERIC CHEMISTRY OF DIMETHYL CARBONATE - REACTION WITH OH RADICALS, UV SPECTRA OF CH3OC(O)OCH2 AND CH3OC(O)OCH2O2 RADICALS, REACTIONS OF CH3OC(O)OCH2O2 WITH NO AND NO2, AND FATE OF CH3OC(O)OCH2O RADICALS

A flash photolysis-resonance fluorescence technique was used to study the rate constant for the reaction of OH radicals with dimethyl carbon ate over the temperature range 252-370 K, The rate constant exhibited a weak temperature dependence, increasing at both low and high tempera ture from a minimum value of approximately 3.1 x 10(-13) cm(3) molecul e(-1) s(-1) near room temperature. Pulse radiolysis/transient UV absor ption techniques were used to study the ultraviolet absorption spectra and kinetics of CH3OC(O)OCH2 and CH3OC(O)CH2O2 radicals at 296 K. Abs orption cross sections of CH3OC(O)OCH2 and CH3OC(O)OCH2O2 at 250 nm we re (3.16 +/- 0.34) x 10(-18) and (3.04 +/- 0.43) x 10(-18) cm(2) molec ule(-1), respectively. Rate constants measured for the self-reactions of CH3OC(O)OCH2 and CH3OC(O)OCH2O2 radicals and reactions of CH3OC(O)O CH2O2 radicals with NO and NO2 were (5.6 +/- 1.1) x 10(-11), (1.27 +/- 0.21) x 10(-11), (1.2 +/- 0.2) x 10(-11), and (1.2 +/- 0.2) x 10(-11) cm(3) molecule(-1) s(-1), respectively. The rate constant for reactio n of F atoms with dimethyl carbonate was determined by a pulse radioly sis absolute rate technique to be (6.1 +/- 0.9) x 10(-11) cm(3) molecu le(-1) s(-1) A FTIR smog chamber system was used to show that, in 760 Torr of air at 296 K, CH3OC(O)OCH2O radicals are lost via three compet ing processes: 42 +/- 15% via reaction with O-2, 14 +/- 2% via H atom elimination, and 44 +/- 10% via decomposition and/or isomerization. Re lative rate techniques were used to measure rate constants for the rea ctions of F atoms with CH3OC(O)OCH3, (6.4 +/- 1.4) x 10(-11) cm(3) mol ecule(-1) s(-1), and Cl atoms with CH3OC(O)OCH3, CH3OC(O)OCH2Cl, CH3OC (O)OCHO, and HC(O)OC(O)OCHO, (2.3 +/- 0.8) x 10(-12), (4.6 +/- 2.8) x 10(-13), (1.7 +/- 0.1) x 10(-13), and (1.7 +/- 0.1) x 10(-14) cm(3) mo lecule(-1) s(-1), respectively. Results are discussed in the context o f the atmospheric chemistry of CH3OC(O)OCH3.