Kinetics of the gas-phase reactions of OH radicals with alkanes and cycloalkanes

Abstract

Abstract. The available database concerning rate constants for gas-phase reactions of the hydroxyl (OH) radical with alkanes through early 2003 is presented over the entire temperature range for which measurements have been made (∼180-2000 K). Measurements made using relative rate methods are re-evaluated using recent rate data for the reference compound (generally recommendations from this review). In general, whenever more than one study has been carried out over an overlapping temperature range, recommended rate constants or temperature-dependent rate expressions are presented. The recommended 298 K rate constants, temperature-dependent parameters, and temperature ranges over which these recommendations are applicable are listed in Table 1.

Development of Predictive Models of the Kinetics of a Hydrogen Abstraction Reaction Combining Quantum-Mechanical Calculations and Experimental Data

“…In Figure 4 the various models developed in this study are presented and compared with the experimental reaction rate data fitted by Atkinson's expression. 10 Inspecting Table 8 and Figure 4, it may be seen that all the models perform well and capture the experimental reaction rate data. The GA model (Figure 4a) performs best, fitting the experimental reaction rate data over the entire temperature range studied with a MAE ln (5)) is also reported, comparing with the experimental reaction rate data for Scheme 1, as shown in Table 5 value of 0.002.…”

“…For cases when the kinetic data fail to comply to the linearity dictated by the Arrhenius equation, satisfactory results are found when analysing those data in terms of the GA expression. 10,114,115 It is important, however, to note that even in the case of highly accurate experimental kinetic data, there might exist several widely different parameter sets that may fit almost equally well the data when using Equation (12); in other words, the inherent uncertainty of estimating the GA parameters is significant.…”

“…Within the parenthesis following the descriptors , the range or the specific point(s) of temperature at which data are fitted is given. Regarding the experimental data, for the entire temperature range the equation of Atkinson 10 is used while for the specific temperature points the experimental values of Talukdar et al 101 tion (Equation (10)), and model GA, which refers to the generalized-Arrhenius equation (Equation (13)), by fitting both of them to the experimental reaction rate data of Atkinson over the temperature range from 200 to 1250 K. 10 Model GA QM refers to the use of the generalized-Arrhenius equation (Equation (13)) fitted to QM-calculated reaction rate constants as computed using CTST/W. It should be noted that model GA QM is purely predictive as it is based entirely on QM calculations.…”

“…In addition to their technological and scientific importance, hydrogen abstraction reactions have a simple mechanism that allows for detailed studies, and hence this class of reactions is very well-documented. 3,4 Reliable sources of data may be found in databases reviewing experimental studies for the gas-phase rate constants for the reactions of hydroxyl radical with alkanes and cycloalkanes spanning temperature ranges from approximately 180 to 2000 K. [5][6][7][8][9][10][11] It is common practice to fit the experimental values to an empirical model, usually the Arrhenius equation, 12 to obtain kinetic parameters. The Arrhenius model contains two parameters: the pre-exponential factor and the activation energy, which are strictly applicable within the temperature interval used in the fitting.…”

Chemical Reactivity as a Tool for Estimating Persistence

“…To rectify this, substantial progress has been made in certain fieldsfor example, the measurement and prediction of atmospheric degradation rates (12). However, regulatory authorities, academics, and those in the chemical industry admit to overreliance on ready biodegradability tests (RBTs) for determining persistence (13).…”