Kinetics Database Resources
Title: Thermal decomposition of 2-fluoroethanol: Single pulse shock tube and ab initio studies
Journal: J. Phys. Chem. A
Page(s): 9782 - 9793
Reference type: Journal article
C2H5OH → C2H4 + H2O
Combined experimental and quantum chemical study of the thermal decomposition of 2-Fluoroethanol or CH2F-CH2OH. Measured decomposition of 2-Fluoroethanol in a shock tube at temperatures of 1000-1200 K and pressures of 13-23 atm. Typical concentrations of 500-1000 ppm 2-Fluoroethanol in Argon. Products detected with GC/FID. Quantum calculations using density functional theory (DFT) with B3LYP/6-311++G(d,p) method. Rate expressions from transition state using TST calculations.
Direct measurements from decomposition products of HF and H2O elimination. Possible C-OH bond fission channel measured indirectly by modeling formation of C2H4 from CH2FCH2OH -> CH2FCH2* + OH and CH2FCH2* -> C2H4 + F with the first step rate C-O bond fission rate determining and the second step C-F beta elimination fast. Also proposed another channel to explain C2H4 formation with HOF elimination or CH2FCH2OH -> C2H4 + HOF. The authors seem to prefer the first C-O bond fission channel, the barrier of about 86 kcal/mol is very similar to the barrier for CH3OH -> CH3 + OH of about 90 kcal/mol. In addition, the authors could find no transition state for elimination of HOF using the quantum calculations. Proposed HOF elimination channel is by analogy to known HOI elimination channel from CH2ICH2Cl. However, C-F bond is significantly stronger and thus HOF elimination is much less likely.
Good agreement (1 kcal/mol) between experimentally derived barriers for HF and H2O elimination and those from the quantum calculations. Also calculated CH3CH2OH -> C2H4 + H2O and compared with rate expression in literature. In this study, also the enthalpy of formation of 2- Fluoroethanol, not available elsewhere, was predicted using MP2/6-311++G(d,p) energies.
Note that initial CH2=CH2(OH) product from HF elimination channel quickly isomerizes to CH3-CHO.
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Rate constant values calculated from the Arrhenius expression: