Absolute rate coefficients over extended temperature ranges and mechanisms of the CF(X2Π) reactions with F2, Cl2 and O2

2009 ◽  
Vol 11 (21) ◽  
pp. 4319 ◽  
Author(s):  
B. Vetters ◽  
B. Dils ◽  
T. L. Nguyen ◽  
L. Vereecken ◽  
S. A. Carl ◽  
...  
Keyword(s):  
Rate Coefficients ◽  
Absolute Rate ◽  
Temperature Ranges

scholarly journals Prediction of absolute rate coefficients and product branching ratios for the C(3P)+allene reaction system

2002 ◽  
Vol 117 (15) ◽  
pp. 7055-7067 ◽  
Author(s):  
Harold W. Schranz ◽  
Sean C. Smith ◽  
Alexander M. Mebel ◽  
Sheng H. Lin
Keyword(s):  
Reaction System ◽  
Branching Ratios ◽  
Rate Coefficients ◽  
Absolute Rate ◽  
Product Branching

Rate Coefficients and Mechanisms for the Atmospheric Oxidation of the Ketones

2011 ◽  
Author(s):  
Jack Calvert ◽  
Abdelwahid Mellouki ◽  
John Orlando ◽  
Michael Pilling ◽  
Timothy Wallington
Keyword(s):  
First Generation ◽  
Rate Coefficient ◽  
Negative Temperature ◽  
Tropospheric Chemistry ◽  
Rate Coefficients ◽  
Anthropogenic Emissions ◽  
Unsaturated Ketones ◽  
Temperature Dependences ◽  
Oh Reactions ◽  
Temperature Ranges

Ketones are emitted directly to the atmosphere, and their sources were discussed in detail in chapter I. In the U.K. acetone and butanone comprise about 7% and 5%, respectively, of the total anthropogenic emissions of oxygenated compounds, and 1.6% and 1.1%, respectively, of the total anthropogenic emissions of nonmethane volatile organic compounds. Ketone emissions from solvents (both industrial and personal) are substantial; emissions from both gasoline- and diesel-fueled vehicles also contribute. Ketones are also formed extensively in the atmosphere in the oxidation of other compounds. Acetone, for example is formed in the OH-initiated oxidation of propane, iso-butane, iso-pentane, and neopentane and from a number of higher hydrocarbons. It is also formed in the oxidation of terpenes. The distribution, sources, and sinks of acetone in the atmosphere have been analyzed by Simpson et al. (1994). Methyl vinyl ketone is an important first generation product in the OH-initiated oxidation of isoprene. In this chapter, we discuss the rate coefficients and the mechanisms of oxidation of ketones. The classes covered include alkanones, hydroxyketones, diketones, unsaturated ketones, ketenes, cyclic ketones, ketones derived from biogenic compounds, and halogen-substituted ketones. Photolysis is a major atmospheric process for many ketones, and will be discussed in chapter IX. The major bimolecular reactions removing ketones from the atmosphere are with OH. Although less important than the OH reactions, reactions with Cl have been studied quite extensively. Other than for unsaturated ketones, reactions with NO3 and O3 are unimportant in tropospheric chemistry and have been studied little. The carbonyl group deactivates the α-position with respect to reaction with OH, but activates the β-position, and possibly more distant sites as well. The net result is that the overall rate coefficient of an alkanone generally exceeds that of the equivalent alkane. The temperature dependences of the rate coefficients can be quite complex, with acetone and possibly butanone showing a minimum in the rate coefficient at ∼250 K, while the higher alkanones show negative temperature dependences across the more limited temperature ranges that have been investigated. The most likely explanation of this behavior is the formation of a pre-reaction, hydrogen-bonded complex.

The Rate-Constant of the Reaction of Hydroxyl Radicals With Methanol, Ethanol and (D3)Methanol

1986 ◽  
Vol 39 (11) ◽  
pp. 1775 ◽  
Author(s):  
PG Greenhill ◽  
BV Ogrady
Keyword(s):  
Hydroxyl Radicals ◽  
Rate Constant ◽  
Flash Photolysis ◽  
Hydrogen Abstraction ◽  
Reaction Scheme ◽  
Resonance Absorption ◽  
Rate Coefficients ◽  
Secondary Reactions ◽  
Temperature Ranges ◽  
Predominant Process

The rate coefficients for hydrogen abstraction by hydroxyl radicals from methanol and ethanol have been determined in the temperature ranges 260-803 K and 255-459 K respectively. Flash photolysis combined with resonance absorption detection of OH was used to obtain results which may be described by the Arrhenius expressions:   Methanol ��� k(T) = (8.0�1.9)×10-12 exp[-(664�88)K/T]cm3 s-1 ������� (1)   Ethanol ���� k(T) = (1.25�0.24)×10-11 exp[-(360�52)K/T]cm3 s-1 (2)  The results obtained for methanol are in excellent agreement with results obtained by other workers, but the Arrhenius parameters for ethanol are markedly different to those obtained in the only other study of the temperature dependence of this reaction. The rate constant for reaction with (D3)methanolhas been determined at 293 K: (D3)Methanol ����� k(293) = 5.0�0.2×10-13 cm3 s-1 (3) The presence of an isotope effect confirms that the predominant process is abstraction of hydrogen from the carbon rather than the oxygen. The results obtained for the reaction with ethanol were analysed by using a 21 reaction scheme to determine the effect of [OH]O and secondary reactions on k(T). The simulations indicate that secondary reactions involving OH are relatively unimportant in determining the bimolecular rate coefficients found in this study.

Absolute rate coefficients for F + H2 and F + D2 at T =295 Ka)

1979 ◽  
Vol 70 (10) ◽  
pp. 4509-4514 ◽  
Author(s):  
R. F. Heidner ◽  
J. F. Bott ◽  
C. E. Gardner ◽  
J. E. Melzer
Keyword(s):  
Rate Coefficients ◽  
Absolute Rate
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