Recommended rate coefficients

The complete set of recommended rate coefficient expressions for the hydrogen-oxygen system is summarized in Table 43. Based on the foregoing discussion, the table includes two alternative, reasonably internally consistent, sets of parameters for the reactions of HO2 with other species. Although neither is completely consistent with the whole range of experimental observations, these sets do, in combination with Table 30, give an impression of the degree of uncertainty still encountered in this particular area. 

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Equations (2.23-2.25) can be used to fit the experimental data using k, and F as temperature dependent variable parameters. In addition, they are widely used to parameterize evaluated or recommended rate coefficients for combustion modelling (Chapter 3) [28]. For the reaction... 

The data for fluorine dissociation has been reviewed critically [84] and the recommended rate coefficient is given by the expression... 

A list of recommended rate coefficients is given in Table 17. This list is based on the work discussed here and that by Gray et al. (1967) and Heicklen (1968). 

The rate coefficient for the reaction of OH with linalool has been measured by Atkinson et al. (1995) and Bernhard and Simonich (2000) using relative rate methods see table II-D-36. The value obtained by Bernhard and Simonich (2000) is about 30% higher than that of Atkinson et al. (1995). The recommended rate coefficient value is... 

The kinetics of the reaction of NO3 with m-cresol have been investigated by Carter et al. (1981) and Atkinson et al. (1984c, 1992b). The data are given in table II-E-8. The lUPAC panel recommended rate coefficient value is based on the measurement... 

The recommended rate coefficient is about 22 times larger than that for OH + acetone abstraction occurs primarily from the —CH2 group which is activated by... 

The reactions of 0( P) with ketene and some of its higher analogs has been reviewed by CvetanoviC (1987). His recommended rate coefficients are summarized in table V-E-23. 

Combining the recommended rate coefficient for reaction with OH radicals with a diurnal average [OH] = 1 x 10 molecule cm gives an estimate of about 1.5 days for the atmospheric lifetime of dimethyl adipate. 

Combining the recommended rate coefficients for reactions with OH radicals and O3 with a daytime average [OH] = 2.5 x 10 molecule cm and a diurnal average [O3] 10 molecule cm gives estimates of about 4 h and about 5 days for the... 

Combining the recommended rate coefficient for reaction with OH radicals with a daytime average [OH] = 2.5 x 10 molecule cm gives an estimate of about 7 h for the daytime atmospheric lifetime of ethyl acrylate. As with alkenes (Calvert et al., 2000) and methacrylates (Blanco et al., 2006), the reaction of OH with ethyl acrylate is believed to proceed via addition to the double bond followed by decomposition of the resulting alkoxy radical. The major oxidation products are CH2O and HC(0)C(0)0C2Hs (ethyl glyoxylate). 

The expressions are valid over the temperature range 200-350 K for air diluent. The coefficients kj, and 2 are the termolecular and high-pressure limit for the association channel, respectively. At 298 K, the recommended rate coefficient value is = 1.5 x 10 molecule cm s with an estimated uncertainty of 10% (lUPAC, 2008). Carl et al. (2001) have shown that the water vapor does not affect the rate coefficient under atmospheric conditions. 

The lUPAC panel recommended rate coefficients values at 298 K are based on these single measurements, but with higher uncertainties, 30%, (Atkinson et al., 2006) ... 

The experiments of Orlando et al. were performed at reduced temperature to avoid thermal decomposition of MPAN in synthetic air at a total pressure of 700-725 Torr. The experiments of Grosjean et al. were also conducted in air at atmospheric pressure but at 298 K. The rate coefficients determined in the two studies differ by a factor of about 10. The lUPAC panel recommended value at 298 K is based on the results of Orlando et al. (2002), adjusted to 298 K using the temperature dependence observed for the OH reaction with propene but with larger uncertainties. The Orlando et al. value was preferred because it is expected that the reaction of OH with MPAN will proceed by addition to the C=C double bond. The recommended rate coefficient is it = 2.9 X 10-... 

It should be emphasized that the recommended rate-coefficient parameters listed are no more than pragmatic representations of experimental data no physical interpretation is made of the significance of the preexponential factor, temperature dependence, or activation energy. The error limits given include allowance for systematic errors, in spite of the difficulty of estimating these, and are therefore larger than the usually stated error limits that only reflect statistical precision of measurements and not true uncertainty of results. 

More exact rate measurements seem to be desirable for this important reaction (Figs. 1 and 4). The recommended rate coefficient is a mean value of the literature data and is supported by the rate coefficient calculated from the reverse reaction (Fig. 43). 

There is large scatter of the rate data (Fig. 65). For the determination of the recommended rate coefficients the older proposals by Benson and Haugen (1967) and Volpi and Zocchi (1966) have been disregarded. 

Only indirect measurements in flames and shock tubes are available in the literature (Fig. 69). This reaction can partly account for the C4H2 formed in rich acetylene flames by C2H + C2H2 C4H2 H- H (Warnatz et al, 1982). The recommended rate coefficient has been chosen to be consistent with the... 

The reverse of this reaction has been discussed before. The recommended rate coefficient takes into account the measurements available in the literature. Unfortunately, the reverse reaction is not known well enough to permit including rate coefficients determined from rate measurements of the reverse reaction. 

Table 33. Recommended rate coefficient parameters for high temperature combustion in the C/H/O System. 

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