On the Uncertainties in the Rate Coefficients for OH Reactions with Hydrocarbons, and the Rate Coefficients of the 1,3,5-Trimethylbenzene and m-Xylene Reactions with OH Radicals in the Gas Phase

Abstract

Rate coefficients for the gas-phase reactions of 1,3,5-trimethylbenzene (TMB) and m-xylene with the OH radical relative to 10 reference compounds were measured yielding (57.3 ± 5.3) × 10-12 and (22.0 ± 2.7) × 10-12 cm3 molecule-1 s-1, respectively (uncertainties are 2σ). These uncertainties arise from a combination of the uncertainty of the reference rate coefficients and experimental errors; thus, the average uncertainty for the rate coefficients of the 10 reference compounds must be less than or equal to the scatter observed in this study. For 16 and 21 measurements with TMB and m-xylene, the observed scatter was ±10% and ±12%, respectively. The average of the uncertainties is significantly smaller than the uncertainties that are frequently assumed or recommended, which range from ±15 to 35%. Absolute rate coefficients for the reaction of TMB and m-xylene with ozone are also reported. Relative rate coefficients for reaction with OH for di-n-butyl ether, methylcyclohexane, cyclopentane, toluene, and cyclohexane of 28.9 ± 2.3, 9.4 ± 0.6, 4.8 ± 0.6, 5.5 ± 0.5, and 7.2 ± 0.6 (×10-12 cm3 molecule-1 s-1) were also measured (uncertainties indicate the whole range of scatter).

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

“…The room temperature rate constants for n-nonane are all from relative rate studies (Atkinson et al, 1982b;Behnke et al, 1987Behnke et al, , 1988Nolting et al, 1988;Ferrari et al, 1996;Kramp and Paulson, 1998), and are in good agreement. A least-squares analysis of the rate constants of Atkinson et al (1982b), Behnke et al (1987Behnke et al ( , 1988, Nolting et al (1988), Koffend andCohen (1996), Ferrari et al (1996) and Kramp and Paulson (1998), using the expression k=AT 2 e −B/T , leads to the recommendation of…”

“…Rate constants are available from the absolute rate studies of Jolly et al (1985), Droege and Tully (1987), Bott and Cohen (1989) and Donahue et al (1998) and from the relative rate studies of Volman (1975), Darnall et al (1978), Atkinson et al (1982a), Kramp and Paulson (1998) and DeMore and Bayes (1999). The study of Atkinson et al (1982a) is judged to supersede the earlier study of Darnall et al (1978), and Fig.…”

“…The study of Atkinson et al (1982a) is judged to supersede the earlier study of Darnall et al (1978), and Fig. 20 shows an Arrhenius plot of the data of Atkinson et al (1982a), Jolly et al (1985), Droege and Tully (1987), Bott and Cohen (1989), Kramp and Paulson (1998), Donahue et al (1998) and DeMore and Bayes (1999). There is an appreciable amount of scatter in the measured room temperature rate constants, with the rate constant of Kramp and Paulson (1998) relative to 1,3-butadiene being lower than the other rate data, and the absolute rate constants of Donahue et al (1998) are both quite scattered and generally higher than the rate constants of Atkinson et al (1982a), Jolly et al (1985), Droege and Tully (1987), Kramp and Paulson (1998) (including those relative to n-nonane, propene and trans-2-butene), and DeMore and Bayes (1999).…”

“…20 shows an Arrhenius plot of the data of Atkinson et al (1982a), Jolly et al (1985), Droege and Tully (1987), Bott and Cohen (1989), Kramp and Paulson (1998), Donahue et al (1998) and DeMore and Bayes (1999). There is an appreciable amount of scatter in the measured room temperature rate constants, with the rate constant of Kramp and Paulson (1998) relative to 1,3-butadiene being lower than the other rate data, and the absolute rate constants of Donahue et al (1998) are both quite scattered and generally higher than the rate constants of Atkinson et al (1982a), Jolly et al (1985), Droege and Tully (1987), Kramp and Paulson (1998) (including those relative to n-nonane, propene and trans-2-butene), and DeMore and Bayes (1999). A least-squares analysis of the rate constants of Atkinson et al (1982a), Jolly et al (1985), Droege and Tully (1987), Bott and Cohen (1989), Kramp and Paulson (1998), Donahue et al (1998) and DeMore and Bayes (1999), using the expression k=AT 2 e −B/T , leads to the recommendation of…”

“…20). A least-squares analysis of the rate constants of Atkinson et al (1982a), Jolly et al (1985), Droege and Tully (1987), Bott and Cohen (1989), Kramp and Paulson (1998) (only the rate constants relative to n-nonane, propene and trans-2-butene, because of the possibility that 1,3-butadiene reacted significantly with NO 2 and/or O( 3 P) atoms, Kramp and Paulson, 1998) and DeMore and Bayes (1999), using the expression k=AT 2 e −B/T , leads to k(cyclopentane)=2.64×10 −17 T 2 e (219±21)/T cm 3 molecule −1 s −1 over the temperature range 270-1200 K, where the indicated uncertainty in the value of B is two least-squares standard deviations, and k(cyclopentane)=4. 298 K (i.e.…”