Kinetics of the reaction of CH/sub 3/S with unsaturated hydrocarbons
The reactions of the methyl thiyl radical, CH/sub 3/S, with 1,3-butadiene and allene have been studied as a function of temperature (296-455 K) and pressure (20-60 Torr) by using laser-induced fluorescence (LIF) as a kinetic probe. The CH/sub 3/S radical adds to 1,3-butadiene to form an adduct. At higher temperatures, an equilibrium was observed, and the approach of the CH/sub 3/S radical to its equilibrium concentration was monitored in real time experiments. These data produce equilibrium constants for a range of temperatures. Arrhenius parameters for the forward reaction, k(+/- 2sigma) = (4.5 +/- 1.3) x 10/sup -13/ exp((0.60 +/- 0.21 kcal/mol)/RT)cm/sup 3//s, and the reverse reaction, k(+/- 2sigma) = (3.7 +/- 22) x 10/sup +13/ exp((-18.4 +/- 4.6 kcal/mol)/RT) s/sup -1/, have also been obtained. Thermodynamic values for the reaction of CH/sub 3/S with 1,3-butadiene (..delta..S/sup 0//sub T/ = -29.7 +/- 8.6 cal/mol K; ..delta..H/sup 0//sub T/ = -18.7 +/- 3.3 kcal/mol; where the errors represent +/- 2sigma) were determined by using a second law procedure. The curved Arrhenius plot for the reaction of CH/sub 3/S with allene was fit to the sum of two Arrhenius expressions k(+/- 2sigma) = (3.2 +/- 24) x 10/sup -11/ exp((-7.2 +/- 8.2 kcal/mol)/RT) + (6.7 +/- 30) x 10/sup -16/ exp((+1.3 +/- 2.6 kcal/mol)/RT) cm/sup 3//s indicating that at least two different reaction channels are occurring over the temperature range studied. Possible mechanisms for the reactions are discussed. Rate constants for the room temperature reaction of CH/sub 3/S with ethylene and propylene as well as upper limits for the reactions with cis-2-butene, acetylene, and methyl acetylene were also measured.
- Research Organization:
- Naval Research Lab., Washington, DC
- OSTI ID:
- 6182034
- Journal Information:
- J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 109:16; ISSN JACSA
- Country of Publication:
- United States
- Language:
- English
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54 ENVIRONMENTAL SCIENCES
ALKYL RADICALS
ALLENE
ARRHENIUS EQUATION
BUTADIENE
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
DATA
DIENES
EQUATIONS
EXPERIMENTAL DATA
FLUORESCENCE
HIGH TEMPERATURE
HYDROCARBONS
INFORMATION
KINETICS
LASERS
LOW PRESSURE
LUMINESCENCE
MEDIUM TEMPERATURE
METHYL RADICALS
NUMERICAL DATA
ORGANIC COMPOUNDS
POLYENES
PRESSURE DEPENDENCE
RADICALS
REACTION KINETICS
TEMPERATURE DEPENDENCE
THIYL RADICALS