Rate Coefficients and Mechanistic Analysis for the Reaction of Hydroxyl Radicals with 1,1-Dichloroethylene and trans-1,2-Dichloroethylene over an Extended Temperature Range

Abstract

Rate coefficients are reported for the gas-phase reaction of the hydroxyl radical (OH) with 1,1-dichloroethylene (k 1 ) and trans-1,2-dichloroethylene (k 2 ) over an extended temperature range at 740 ( 10 Torr in a He bath gas. Absolute rate measurements were obtained using a laser photolysis/laser-induced fluorescence (LP/LIF) technique under slow flow conditions. Rate measurements for k 1 exhibited complex behavior with negative temperature dependence at temperatures below 640 K, a rapid falloff in rate between 650 and 700 K, and positive temperature dependence from 700 to 750 K. The simple Arrhenius equation adequately describes the data below 640 K and above 700 K and is given (in units of cm 3 molecule -1 s -1 ) by k 1 (291-640 K) ) (1.81 ( 0.36) × 10 -12 exp(511 ( 71)/T and k 1 (700-750 K) ) 3.13 × 10 -10 exp(-5176/T). Rate measurements for k 2 also exhibited complex behavior with a near-zero or slightly negative temperature dependence below 500 K and a near-zero or slightly positive temperature dependence above 500 K. The modified Arrhenius equation adequately describes all of the data and is given (in units of cm 3 molecule) by k 2 (293-720 K) ) (9.75 ( 1.14) × 10 -18 T 1.73( 0.05 exp(727 ( 46)/T. Error limits are 2σ values. The room-temperature values for k 1 and k 2 are within (2σ of previous data using different techniques. The rate measurements were modeled using QRRK theory. OH addition to the unsubstituted carbon followed by adduct stabilization describes the low-temperature measurements for k 1 . Analysis of equilibration in this system yields a C-O bond dissociation enthalpy of 32.8 ( 1.5 kcal mol -1 at 298 K, a value confirmed by ab initio calculations. OH addition followed by Cl elimination described the experimental data for k 2 . Ab initio based transition state calculations for the H atom abstraction channel indicated that this mechanism is consistent with the rate measurements for k 1 above 700 K. The H abstraction channel for k 2 could not be observed because of the presence of a more rapid Cl elimination channel at elevated temperatures. H abstraction is predicted to be the dominant reaction channel for both k 1 and k 2 at flame temperatures.

The reaction of OH with acetaldehyde and deuterated acetaldehyde: Further insight into the reaction mechanism at both low and elevated temperatures

“…The apparatus and experimental procedures are well established [16][17][18]. In brief, OH was generated in the presence of a large excess of CH 3 CHO by excimer laser photolysis of a precursor, and monitored by off-resonance laser-induced fluorescence excited at 282 nm.…”

Rate Coefficients and Mechanistic Analysis for Reaction of OH with Vinyl Chloride between 293 and 730 K

“…This behavior does not, however, necessarily imply that the reaction was at the high-pressure limit at lower temperatures. As a matter of fact, we recently reported QRRK calculations for a similar compound, vinylidene chloride, indicating that OH addition is pressure-dependent at atmospheric pressure at temperatures considerably lower than 600 K. 10 These modeling results are consistent with the data of Howard 6 who reported a pressure dependence for reaction of OH with vinyl chloride at 296 K. As noted by Liu et al, 8 these studies, performed in 1 to 7 Torr of helium indicated the following: (1) there is a substantial pressure dependence on these rate constants at room temperature suggesting that the rate at room temperature depends significantly on collisional deactivation, (2) the rate constants continue to increase at 7 Torr of helium, thus explaining the lower magnitude of the rate constant compared with Perry et al 7 and Liu et al, 8 and (3) the rate constant extrapolated to zero pressure * To whom correspondence should be addressed. Fax: (937) 229-2503. e-mail: taylorph@udri.udayton.edu.…”

Atmospheric chemistry of (Z)- and (E)-1,2-dichloroethene: kinetics and mechanisms of the reactions with Cl atoms, OH radicals, and O3

“…As discussed in the following section, Cl atoms are very likely eliminated during the reaction and the majority of the experiments were conducted in the presence of c-C 6 H 12 in large excess. Linear least-squares analysis of the data in Figure 7 7 Tuazon et al 1 and Yamada et al, 4 but significantly lower than the values of Canosa-Mas et al 2 (for (E)-CHClQCHCl) and of Zhang et al 6 (for (Z)-CHCl QCHCl and (E)-CHClQCHCl)). As both these latter studies used the changes in OH fluorescence signal to determine the reactivity of (E)-CHClQCHCl, any Cl atoms eliminated from the OH adduct cannot account for the measured enhancement in reactivity.…”

“…Canosa-mas et al 2 measured a faster rate constant for the reaction of OH radicals with ( E )-CHClCHCl, at 1.6 Torr and at 298 K using a discharge-flow technique and reported a value of k 26 = (2.5 ± 0.3) × 10 −12 cm 3 molecule −1 s −1 . Zhang et al 6 measured the kinetics as a function of temperature (240–400 K) for both ( Z )-CHClCHCl and ( E )-CHClCHCl and determined values of k 25 = (2.71 ± 0.28) × 10 −12 and k 26 = (2.50 ± 0.30) × 10 −12 cm 3 molecule −1 s −1 at 298 K. Finally, Yamada et al 4 used laser photolysis/laser-induced fluorescence technique under slow flow conditions at a pressure of 740 Torr to determine k 26 = (2.24 ± 0.31) × 10 −12 cm 3 molecule −1 s −1 at 293 K. Within the stated uncertainties, the rate constants of the present work is in agreement with the previous work of Abbatt and Anderson, 7 Tuazon et al 1 and Yamada et al , 4 but significantly lower than the values of Canosa-Mas et al 2 (for ( E )-CHClCHCl) and of Zhang et al 6 (for ( Z )-CHClCHCl and ( E )-CHClCHCl)). As both these latter studies used the changes in OH fluorescence signal to determine the reactivity of ( E )-CHClCHCl, any Cl atoms eliminated from the OH adduct cannot account for the measured enhancement in reactivity.…”

“…Chloroethenes are important industrial chemicals whose atmospheric chemistry has been subject of several previous studies. [1][2][3][4][5][6][7] The industrial use of 1,2-dichloroethene, CHClQCHCl is mainly as a chemical intermediate in the synthesis of chlorinated solvents and other compounds. The (E)-isomer is in greater industrial use than the (Z)-isomer.…”