Kinetic studies of the reactions CH3+NO2 -> products, CH3O+NO2 -> products, and OH+CH3C(O)CH3 -> CH3C(O)OH+CH3, over a range of temperature and pressure

The title reactions were investigated using pulsed laser photolysis combine d with pulsed laser induced fluorescence detection of CH3O to determine the rate coefficients fur CH3 + NO2 --> products (3) and CH3O + NO2 --> produc ts (5) as a function of temperature and pressure, and to estimate the yield of CH3 (and thus: the yield of CH3C(O)OH) from the reaction of OH with CH3 C(O)CH3 (2) at two different temperatures. Reaction 3 has both bimolecular and termolecular components: a simplified falloff parametrization with F-ce nt = 0.6 gives k(3b)(0) = (3.2 +/- 1.3) x 10(-28)(T/297)(-0.3) cm(6) s(-1) and k(3b)(infinity) = (4.3 +/- 0.4) x 10(-11)(T/297)(-1.2) cm(3) s(-1) with CH3NO2 the likely product. The rate constant for the bimolecular reaction pathway to form CH3O + NO (3a) was found to be 1.9 x 10(-11) cm(-3) s(-1). The low- and high-pressure limiting rate coefficients for reaction between CH3O and NO2 to form CH3ONO2 (5b) were derived as k(5b)(0) = (5.3 +/- 0.3) x 10(-29)(T/297)(-4.4) cm(6) s(-1) and k(5b)(infinity) = (1.9 +/- 0.05) x 1 0(-11)(T/297)(-1.9) cm(3) s(-1), respectively. Although the final result is associated with some experimental uncertainty, we find that CH3 is formed in the reaction between OH and CH3C(O)CH3 at approximate to 50% yield at ro om temperature and 30% at 233 K.