文摘
Kinetics of four carbon-centered, oxygen-containing free radical reactions with nitric oxide (NO) were investigated as a function of temperature at a few Torr pressure of helium, employing flow tube reactors coupled to a laser-photolysis/resonance-gas-discharge-lamp photoionization mass spectrometer (LP-RPIMS). Rate coefficients were directly determined from radical (R) decay signals under pseudo-first-order conditions ([R]<sub>0sub> 鈮?[NO]). The obtained rate coefficients showed negative temperature dependences, typical for a radical鈥搑adical association process, and can be represented by the following parametrizations (all in units of cm<sup>3sup> molecule<sup>鈥?sup> s<sup>鈥?sup>): k(CH<sub>2sub>OH + NO) = (4.76 脳 10<sup>鈥?1sup>) 脳 (T/300 K)<sup>15.92sup> 脳 exp[50700/(RT)] (T = 266鈥?63 K, p = 0.79鈥?.44 Torr); k(CH<sub>3sub>CHOH + NO) = (1.27 脳 10<sup>鈥?6sup>) 脳 (T/300 K)<sup>6.81sup> 脳 exp[28700/(RT)] (T = 241鈥?63 K, p = 0.52鈥?.43 Torr); k(CH<sub>3sub>OCH<sub>2sub> + NO) = (3.58 卤 0.12) 脳 10<sup>鈥?2sup> 脳 (T/300 K)<sup>鈭?.17卤0.14sup> (T = 221鈥?63 K, p = 0.50鈥?.80 Torr); k(T)<sub>3sub> = 9.62 脳 10<sup>鈥?1sup> 脳 (T/300 K)<sup>鈭?.99sup> 脳 exp[鈭?100/(RT)] (T = 221鈥?73 K, p = 1.41鈥?.95 Torr), with the uncertainties given as standard errors of the fits and the overall uncertainties estimated as 卤20%. The rate of CH<sub>3sub>OCH<sub>2sub> + NO reaction was measured in two density ranges due to its observed considerable pressure dependence, which was not found in the studied hydroxyalkyl reactions. In addition, the CH<sub>3sub>CO + NO rate coefficient was determined at two temperatures resulting in k<sub>298Ksub>(CH<sub>3sub>CO + NO) = (5.6 卤 2.8) 脳 10<sup>鈥?3sup> cm<sup>3sup> molecule<sup>鈥?sup> s<sup>鈥?sup>. No products were found during these experiments, reasons for which are briefly discussed.