Pressure and temperature dependence of the OH radical reaction with acetylene

Perry, R. A.; Williamson, David T.

doi:10.1016/0009-2614(82)83703-2

Cited by 27 publications

(25 citation statements)

References 9 publications

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“…By comparison of this curve with computer simulations (full and dashed lines in Fig. 3) it could be proved that under tropospheric conditions the loss of OH by reactions competing with the processes (6) and (7) is less than lo%, i.e. that more than 90% of the OH is recycled in the catalytic SOz oxidation mechanism (5) to (7).…”

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confidence: 90%

Study of OH Reactions at High Pressures by Excimer Laser Photolysis — Dye Laser Fluorescence

Schmidt

Zhu

Becker

et al. 1985

Ber Bunsenges Phys Chem

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Reactions of hydroxyl radicals have been studied up to total pressures of 1 atm and in the presence of strongly quenching gases by using excimer laser photolysis of H 2 0 2 or H N 0 3 for the generation and pulsed dye laser fluorescence for monitoring the concentration of the radicals as a function of reaction time. Results are reported of a study of the effects of molecular oxygen on the reactions of OH with acetylene and with some sulfur containing compounds (e.g. CS2).The high sensitivity of the pulsed dye laser induced fluorescence technique (LIF) allows absolute rate constant measurements of OH reactions under tropospheric conditions, i.e. up to total pressures of 1 atm and in the presence of strongly quenching gases like O2 and H 2 0 . We report on measurements in which excimer laser photolysis is used for the pulsed generation of OH radicals from H 2 0 2 or HN'03 parent gases and where a pulsed, frequency doubled, high energy dye laser serves for monitoring the time decay of the OH concentration in an excess of reactant gas by LIF of the OH(A2Ct t , X2H) transition near 300 nm [l].In order to check the method and the apparatus, test measurements were performed in synthetic air at a total pressure of 1 atm with H2 and some simple alkanes and alkenes. The results (Table 1) are in reasonable agreement with literature data. cm6 s-', Cm3 S -' , cm3 s -' which are in good agreement with recent results of Wahner ut al. [S] obtained with a laser photolysis/laser absorption technique. In the presence of oxygen, the OH decay curves were found to be bi-exponential (Fig. 2). Such behaviour is characteristic for systems in which O H radicals are regencrated by fast secondary reactions. This was verified by n-C4Hlo -The reaction of OH with CzH2 was studied in detail to clarify some discrepancies in the literature data on the rate constant of this reaction [2 -63 in particular concerning the different results for its pressure dependence for He and Ar buffer gases and the contribution of a bimolecular process to the reaction. Fig. 1 shows the results for He, Ar, and N2.Similar pressure dependences are observed for these inert who measured pressure independent rate constants in He buffer gas. Also, the zero pressure intercept, i.e. the pressure independent bimolecular contribution to the rate constant, is found to be about a factor of 10 lower than given in the

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confidence: 90%

Study of OH Reactions at High Pressures by Excimer Laser Photolysis — Dye Laser Fluorescence

Schmidt

Zhu

Becker

et al. 1985

Ber Bunsenges Phys Chem

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“…The pressure dependence has been studied extensively at room temperature; 16,18,19,22,23,33,34,39 but, data at other temperatures are limited. 16 At higher temperatures, direct hydrogen abstraction, as well as isomerization of the addition complex and subsequent dissociations, giving rise to several bimolecular channels:…”

Section: Introductionmentioning

confidence: 99%

The Reaction of Acetylene with Hydroxyl Radicals

2005

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The potential energy surface for the reaction between OH and acetylene has been calculated using the RQCISD(T) method and extrapolated to the complete basis-set limit. Rate coefficients were determined for a wide range of temperatures and pressures, based on this surface and the solution of the one-dimensional and two-dimensional master equations. With a small adjustment to the association energy barrier (1.1 kcal/mol), agreement with experiments is good, considering the discrepancies in such data. The rate coefficient for direct hydrogen abstraction is significantly smaller than that commonly used in combustion models. Also in contrast to previous models, ketene + H is found to be the main product at normal combustion conditions. At low temperatures and high pressures, stabilization of the C2H2OH adduct is the dominant process. Rate coefficient expressions for use in modeling are provided.

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“…The sterically hindered fert-butyl substituted nitrobenzyl halides (7, 12) exhibit lower A values than the corresponding nonhindered compounds (5, 8), indicating that the decreased rates of dehalogenation in these anion radicals are indeed owing to steric effects. 7 On the other hand, while the activation energy for the chloro derivatives (5, 7) increases upon substitution with the terf-butyl group, it decreases considerably in the case of the bromo derivatives (8,12). The latter decrease is somewhat unexpected, unless one assumes that the bulkiness of both -Bu and Br (in 12) causes a decrease in the C-Br bond energy.…”

Section: Resultsmentioning

confidence: 99%

“…In similar fashion treatment of 3-nitro-o-xylene gave the following: 2-Methyl-6-nitrobenzyl bromide: mp 61-62 °C (CH2Cl2/light petroleum); 'H NMR 2.52 (s, 3 H, Me), 4.71 (s, 2 H, CH2), 7.32 (dd, 1 , H4, J = 7.5 and 7.8 Hz), 7.45 (dd, 1 , H3, J = 7.8 and 2.0 Hz), 7.72 (dd, 1 , H5, J = 7.5 and 2.0 Hz); IR Found: C, 41.73; H, 3.54; N, 6.08. 2-Methyl-3-nitrobenzyl bromide: mp 155/0.7 mmHg (Kugelrohr); >H NMR 2.51 (s, 3 H, Me), 4.54 (s, 2 H, CH2), 7.28 (dd, 1 , H5, J = 7.6 and 7.9 Hz), 7.55 (dd, 1 , H6, J = 7.6 and 1.5 Hz), 7.71 (dd, 1 , H4, J = 7.9 and 1.5 Hz); IR (CHC13) 1525, 1350 cm"1; UV (EtOH) 223 nm (e 1.52 X 104); mass spectrum, mjz 231 (M+ + 2, 9%), 229 (M+, 9), 214 (8), 212 (8), 150 (100), 132 (14), 104 (36), 103 (87), 92 (28), 91 (26), 78 (38), 77 (54), 63 (17).…”

Section: Methodsmentioning

confidence: 99%