Reactions of the cyanogen radical with molecules relevant to atmospheric and combustion chemistry
The reactions of the CN radical are important in the photochemistry of planetary atmospheres and fuel combustion systems. Despite the importance of these reactions, few studies of the pressure and temperature dependency of the rates have been performed. Employing the method of laser photolysis/laser-induced fluorescence to measure the rate of CN loss over broad ranges of temperature (175-750 K) and pressure (50-810 torr), the bimolecular rate constants for CN reactions with a variety of molecules, which are abundant in the atmosphere of Titan and which occur during the burning of several nitramine fuels, have been measured. These molecules included alkanes, cycloalkanes, unsaturated hydrocarbons, N[sub 3], H[sub 2], C[sub 2]N[sub 2], HCN, NO, NO[sub 2], N[sub 2]O, and CO[sub 2]. The reactions of CN with these molecules were found to occur through simple H-atom abstraction (alkanes, cyclolkanes, H[sub 2]), pressure-independent addition (unsaturated hydrocarbons, C[sub 2]N[sub 2], HCN, N[sub 2]O), and pressure-dependent combination (NO). In the case of CO[sub 2], no reaction could be detected up to 740K. Additional experiments employing D[sub 2], CD[sub 4], and ND[sub 3] allowed for the study of the isotope effect over a broad temperature range. Calculations employing statistical theories such as the transition state theory (TST), variational TST, Rice-Ramsperger-Kassel-Marcus (RRKM) theory, the Forst's approximation for the specific (micro-canonical) rate constants in RRKM calculations were then applied in order to rationalize, reproduce, and extrapolate the measured rates to high (combustion) and low (planetary atmosphere) temperatures. It was determined that simple transition state theory and RRKM theory were able to model the experimental rates only when the position of the transition state for the particular process was clearly defined.
- Research Organization:
- Emory Univ., Atlanta, GA (United States)
- OSTI ID:
- 7226576
- Resource Relation:
- Other Information: Thesis (Ph.D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ALKANES
CHEMICAL REACTION KINETICS
CYANOGEN
CYCLOALKANES
HYDROGEN
NITROGEN
NITROGEN OXIDES
COMBUSTION KINETICS
PLANETARY ATMOSPHERES
ATMOSPHERES
CHALCOGENIDES
ELEMENTS
HYDROCARBONS
KINETICS
NITROGEN COMPOUNDS
NONMETALS
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
REACTION KINETICS
540120* - Environment
Atmospheric- Chemicals Monitoring & Transport- (1990-)
400800 - Combustion
Pyrolysis
& High-Temperature Chemistry