A pulse radiolysis technique has been used to measure the UV spectra of CH3SCH2 and CH3SCH2O2 radicals over the range 225-350 nm. At 285 nm, sigma(CH3SCH2) = (9.8 +/- 1.7) x 10(-18); at 250 nm, sigma(CH3SCH2O2) = (4.3 +/- 0.7) x 10(-18) cm2 molecule-1. Observed self-reaction rate constants, defined as -d[CH3SCH2]/dt = 2k6[CH3SCH2]2 and -d[CH3sCH2O2[/dt = 2k7obs[CH3SCH2O2]2, were k6 = (3.0 +/- 0.6) x 10(-11) and k7obs. = (7.9 +/- 1.4) x 10(-12) cm3 molecule-1 s-1. Errors are statistical (2 standard deviations) plus our estimate of potential systematic uncertainty (15%). A rate constant, k2 = (5.7 +/- 0.4) X 10(-12) cm3 molecule-1 S-1, was derived for the addition reaction CH3SCH2 + O2 --> CH3SCH2O2. A rate constant, k3 = (1.9 +/- 0.6) x 10(-11) cm3 molecule-1 s-1, is reported for the reaction of CH3SCH2O2 radicals with NO, producing NO2. Errors for k2 and k3 are 2 standard deviations. Results are discussed with respect to the atmospheric chemistry of dimethyl sulfide.
Rate coefficients for the gas-phase reaction of OH radicals with dimethyl sulfide: temperature and O<sub>2</sub>partial pressure dependence
作者:Mihaela Albu、Ian Barnes、Karl H. Becker、Iulia Patroescu-Klotz、Raluca Mocanu、Thorsten Benter
DOI:10.1039/b512536g
日期:——
coefficients for the gas-phase reaction of hydroxyl (OH) radicals with dimethyl sulfide (CH(3)SCH(3), DMS) have been determined using a relative rate technique. The experiments were performed under different conditions of temperature (250-299 K) and O(2) partial pressure (approximately 0 Torr O(2)-380 Torr O(2)), at a total pressure of 760 Torr bath gas (N(2) + O(2)), in a 336 l reaction chamber, using long path
Amatore, C.; Bayachou, M.; Bontejengout, F., Bulletin de la Societe Chimique de France, 1993, vol. 130, # 3, p. 371 - 381
作者:Amatore, C.、Bayachou, M.、Bontejengout, F.、Verpeaux, J. N.
DOI:——
日期:——
Temperature-Dependent Kinetics Studies of the Reactions Br(2P3/2) + CH3SCH3 .dblarw. CH3SCH2 + HBr. Heat of Formation of the CH3SCH2 Radical
作者:A. Jefferson、J. M. Nicovich、P. H. Wine
DOI:10.1021/j100080a006
日期:1994.7
Time-resolved resonance fluorescence detection of Br(P-2(3/2)) atom disappearance or appearance following 266-nm laser flash photolysis of CF2Br2/CH3SCH3/H-2/N-2 and Cl2CO/CH3SCH3/HBr/H-2/N-2 mixtures has been employed to study the kinetics of the reactions Br(P-2(3/2)) + CH3SCH3 <----> HBr + CH3SCH2 (1,-1) as a function of temperature over the range 386-604 K. Arrhenius expressions in units of cm(3) molecule(-1) s(-1) which describe the results are k(1) = (9.0 +/- 2.9) X 10(-11) exp[(-2386 +/- 151)/T]} and k(-1) = (8.6 +/- 2.5) X 10(-13) exp[(836 +/- 140)/T]}; errors are 2 sigma and represent precision only. To our knowledge, these are the first kinetic data reported for each of the two reactions studied. Second and third law analyses of the equilibrium data for reactions 1 and -1 have been employed to obtain the following enthalpies of reaction in units of kcal mol(-1): Delta H-298 = 6.11 +/- 1.37 and Delta H-0 = 5.37 +/- 1.38. Combining the above enthalpies of reaction with the well-known heats of formation of Br, HBr, and CH3SCH3 gives the following heats of formation of the CH3SCH2 radical in units of kcal mol(-1): Delta H-f,H-298 = 32.7 +/- 1.4 and Delta H-f,H-0,o = 35.3 +/- 1.4; errors are 2 sigma and represent estimates of absolute accuracy. The C-H bond dissociation energy in CH3SCH3 obtained from our data, 93.7 +/- 1.4 kcal mol(-1) at 298 K and 92.0 +/- 1.4 kcal mol(-1) at 0 K, agrees well with a recent molecular beam photofragmentation study but is 3 kcal mol(-1) lower than the value obtained from an iodination kinetics study.
Moenig; Goslich; Asmus, Berichte der Bunsengesellschaft/Physical Chemistry Chemical Physics, 1986, vol. 90, # 2, p. 115 - 121
作者:Moenig、Goslich、Asmus
DOI:——
日期:——
Atmospheric chemistry of dimethyl sulfide: UV spectra and self-reaction kinetics of CH3SCH2 and CH3SCH2O2 radicals and kinetics of the reactions CH3SCH2 + O2 .fwdarw. CH3SCH2O2 and CH3SCH2O2 + NO .fwdarw. CH3SCH2O + NO2
作者:Timothy J. Wallington、Thomas Ellermann、Ole J. Nielsen
DOI:10.1021/j100134a013
日期:1993.8
A pulse radiolysis technique has been used to measure the UV spectra of CH3SCH2 and CH3SCH2O2 radicals over the range 225-350 nm. At 285 nm, sigma(CH3SCH2) = (9.8 +/- 1.7) x 10(-18); at 250 nm, sigma(CH3SCH2O2) = (4.3 +/- 0.7) x 10(-18) cm2 molecule-1. Observed self-reaction rate constants, defined as -d[CH3SCH2]/dt = 2k6[CH3SCH2]2 and -d[CH3sCH2O2[/dt = 2k7obs[CH3SCH2O2]2, were k6 = (3.0 +/- 0.6) x 10(-11) and k7obs. = (7.9 +/- 1.4) x 10(-12) cm3 molecule-1 s-1. Errors are statistical (2 standard deviations) plus our estimate of potential systematic uncertainty (15%). A rate constant, k2 = (5.7 +/- 0.4) X 10(-12) cm3 molecule-1 S-1, was derived for the addition reaction CH3SCH2 + O2 --> CH3SCH2O2. A rate constant, k3 = (1.9 +/- 0.6) x 10(-11) cm3 molecule-1 s-1, is reported for the reaction of CH3SCH2O2 radicals with NO, producing NO2. Errors for k2 and k3 are 2 standard deviations. Results are discussed with respect to the atmospheric chemistry of dimethyl sulfide.