A temperature‐dependent kinetics study of the reaction of O(³P_J) with (CH₃)₂SO

Abstract

A laser flash photolysis-resonance fluorescence technique has been employed to investigate the kinetics of the reaction of ground state oxygen atoms, O( 3 P J ), with (CH 3 ) 2 SO (dimethylsulfoxide) as a function of temperature (266-383 K) and pressure (20-100 Torr N 2 ). The rate coefficient (k R1 ) for the O( 3 P J ) + (CH 3 ) 2 SO reaction is found to be independent of pressure and to increase with decreasing temperature. The following Arrhenius expression adequately describes the observed temperature dependence: k R1 (T ) = (1.68 ± 0.76) × 10 −12 exp[(445 ± 141)/T ] cm 3 molecule −1 s −1 , where the uncertainties in Arrhenius parameters are 2σ and represent precision only. The absolute accuracy of each measured rate coefficient is estimated to be ±30%, and is limited predominantly by the uncertainties in measured (CH 3 ) 2 SO concentrations. The observed temperature and pressure dependencies suggest that, as in the case of O( 3 P J ) reactions with CH 3 SH and (CH 3 ) 2 S, reaction occurs by addition of O( 3 P J ) to the sulfur atom followed by rapid fragmentation of the energized adduct to products. The O( 3 P J ) + (CH 3 ) 2 SO reaction is fast enough so that it could be a useful laboratory source of the CH 3 SO 2 radical if this species is produced in significant yield.

Kinetics and Mechanism of the O Atom Reaction with Dimethyl Sulfoxide

“…Kinetics of reaction 1 between O atoms and DMSO has been investigated in only one previous study by Pope et al, where laser flash photolysis in combination with resonance fluorescence detection of O atoms was used to measure the reaction rate constant in the pressure range (20−100) Torr and temperatures between 266 and 383 K. The rate constant of reaction 1 was found to be independent of pressure and to increase with decreasing temperature. The room-temperature value of k 1 determined in ref , k 1 = (7.5 ± 2.2) × 10 -12 cm 3 molecule -1 s -1 , can be compared with that from the present work: k 1 = (1.0 ± 0.2) × 10 -11 cm 3 molecule -1 s -1 at T = 298 K and P = 1 Torr of He. One can note good agreement between these two values of k 1 obtained under different experimental conditions with different experimental techniques.…”

“…Therefore, the above discussion based on thermochemical consideration supports the experimental results suggesting that reaction 1a is predominant channel. Thermochemical consideration by Pope et al also led these authors to speculate that reaction 1 proceeds via channel 1a.…”

“…The results presented in Figure 6 show that there is no linear dependence between consumed O atom concentration and the concentration of products formed. The reason for this is that the fast secondary reactions O + CH 3 (12) and CH 3 + CH 3 (2) cannot be made negligible, and they (especially reaction 12) influence significantly the yield of the products. The dashed line in Figure 6 represents a yield of unity for SO 2 formation.…”

“…The present paper reports the results of the experimental study of the kinetics and products of the reaction 1 at room temperature and 1 Torr total pressure of helium When this paper was in preparation, the results of another kinetic study of reaction 1 were reported. 12 In that study, the reaction rate constant was measured as a function of temperature (266-383 K) and pressure (20-100 Torr of N 2 ); however, the primary reaction products remain unknown.…”

Environmental effects of large igneous province magmatism: a Siberian perspective

“…The recommended 298 K rate constant is the average of values reported from a laser flash photolysis -resonance fluorescence study by Pope et al [1068], and from a discharge flow − mass spectrometry study by Riffault et al [1119]. A rate constant reported by Barnes et al [76] (with no details about how the rate constant was obtained) is somewhat faster than the recommendation, but in agreement to within the recommended uncertainty factor.…”