Determination of Arrhenius parameters for unimolecular reactions of chloroalkanes by IR laser pyrolysis

Journal Article · Mon Nov 01 04:00:00 EST 1982 · J. Chem. Phys.; (United States)

DOI:https://doi.org/10.1063/1.444398· OSTI ID:7083159

Dai, H; Specht, E; Berman, M R; Moore, C B

A simple and reliable method is elaborated for accurate measurements of thermal rate constants of homogeneous gas phase unimolecular reactions. A pulse of CO/sub 2/ laser radiation was used to multiphoton excite SiF/sub 4/ sensitizer molecules and consequently produce temperatures in the range 1100--1400 K. Expansion of the heated gas column quenches pyrolysis reactions on a 10 ..mu..s time scale. There are no hot surfaces to induce chemistry. HCl elimination from C/sub 2/H/sub 5/Cl, E/sub a/ = 57.4 kcal/mol and log A(s/sup -1/) = 13.8, was used as an internal temperature standard. For the molecular elimination CCl/sub 3/CH/sub 3/ ..-->.. HCl+CCl/sub 2/CH/sub 2/, E/sub a/ = 49.5 +- 1.3 kcal/mol and log A(s/sup -1/) = 13.1 +- 0.3, were determined. In these experiments the major decomposition products of CHCl/sub 2/CH/sub 2/Cl are HCl and cis- or trans-CHClCHCl with E/sub a/ = 58.5 +- 2, log A = 14.1 +- 0.4 and E/sub a/ = 59.5 +- 2, log A = 13.9 +- 0.4, respectively. HCl elimination to give CCl/sub 2/CH/sub 2/ and C--Cl bond breaking to CHClCH/sub 2/Cl radical have higher activation energies. The method is generally useful for kinetics at high temperature.

• Research Organization: Department of Chemistry, University of California, Material and Molecular Research Division of the Lawrence Berkeley Laboratory, Berkeley, California 94720
• OSTI ID: 7083159
• Journal Information: J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 77:9; ISSN JCPSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400301* -- Organic Chemistry-- Chemical & Physicochemical Properties-- (-1987)
ACTIVATION ENERGY
ARRHENIUS EQUATION
CARBON DIOXIDE LASERS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHLORINATED ALIPHATIC HYDROCARBONS
DECOMPOSITION
ELECTROMAGNETIC RADIATION
ENERGY
EQUATIONS
GAS LASERS
HALOGENATED ALIPHATIC HYDROCARBONS
INFRARED RADIATION
KINETICS
LASER RADIATION
LASERS
ORGANIC CHLORINE COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
PYROLYSIS
RADIATIONS
REACTION KINETICS
THERMOCHEMICAL PROCESSES
VERY HIGH TEMPERATURE