3834-39-7Relevant academic research and scientific papers
KrF laser induced telomerization of bromides with olefins. Part 1. Self-inhibition and kinetic analysis
Linyang,Fuss,Kompa
, p. 867 - 874 (1990)
The chain reaction of several organic bromides with olefins was induced by a KrF laser. In all cases we found a self-inhibition, leading to a termination of first order in the radical concentration. There is indirect evidence that it is due to molecular bromine, accumulated during the reaction in spite of the presence of olefins. It has not been noticed previously. We show that kinetic analysis is easy also for pulsed excitation, and the example CF3Br + C2H4 is studied in detail. We found rate constants for CF3 + C2H4 → CF3C2H4 (7.2·109 cm3 mol-1 s-1; this is in between two previous values) and for CF3C2H4 + CF3Br → CF3C2H4Br + CF3(1.2·109 cm3 mol-1 s-1) as well as preliminary values for some other reactions.
Substituent effects on the disproportionation-combination rate constant ratios for gas-phase halocarbon radicals. II. Reactions of · CF3 + CF3CH2CH2 · and CF3CH2CH2· + CF3CH2CH2·
McDowell, Derek R.,Weston, Jennie,Holmes, Bert E.
, p. 61 - 68 (2007/10/03)
Disproportionation/combination rate constant ratios, kd/kc. have been measured for the collision between CF3CH2CH2 and CF3 radicals to be 0.022 ± 0.002 and for CF3CH2CH2 and CF3CH2CH2 radicals to be 0.100 ± 0.002. Comparison to previous work from this laboratory for the reaction of CF3CH2CHCl with CF3 radicals shows that substitution of Cl for H increases the kd/kc by about 50%; however, for the auto disproportionation-combination of CF3CH2CH2 radicals the chlorine substituent decreases the observed rate constant ratio by a factor of two. The chlorine substituent effect on the observed kd/kc ratios is compared to predictions from molecular orbital calculations.
Fluorine substitution effects on the alkyl coupling reaction on a Ag(111) surface
Paul, Anumita,Gellman, Andrew J.
, p. 9056 - 9066 (2007/10/03)
We have investigated fluorine substitution effects on the rate of coupling of adsorbed alkyl groups on a Ag(111) surface. Alkyl groups are formed by thermal dissociation of the C-I bond in adsorbed alkyl iodides. Variable heating rate temperature programmed reaction (TPR) studies were used to determine the kinetic parameters for the coupling of ethyl groups and propyl groups. They are Ea = 15.1 ± 0.6 kcal/mol, v = 1016.7±0.8 s-1 and Ea = 16.9 ± 0.4 kcal/mol, v = 1017.1±0.4 s-1, respectively. Substitution of fluorine for hydrogen in the adsorbed alkyl groups systematically raises the coupling reaction temperature. For example, trifluoropropyl groups self-couple at temperatures ～70 K higher than propyl groups on Ag(111). Coadsorbed propyl and trifluoropropyl groups cross-couple at temperatures ～10 K higher than the propyl self-coupling reaction. The kinetic parameters evaluated from the results of this study and from results of earlier studies by X.-L. Zhou, J. M. White, and co-workers [Surf. Sci. 1989, 219, 294; Catal. Lett. 1989, 2, 375; J. Phys. Chem. 1991, 95, 5575] are used to plot linear free energy relationships (LFER) which provide insight into the electronic nature of the reaction center. The implication of the LFER plots for the surface alkyl coupling reaction is that the reaction center in the transition state is electron deficient with respect to the initial state.
KINETICS OF REACTIONS OF C3., C5. AND C7. ALKYL RADICALS FORMED IN THE CF3. + C2H4 SYSTEM, I. DETERMINATION OF THE RATE COEFFICIENTS
Dobe, Sandor,Berces, Tibor,Marta, Ferenc
, p. 43 - 58 (2007/10/02)
n-Propyl, n-pentyl and n-heptyl free radicals (with perfluorinated methyl groups) were generated by the photolysis of perfluoroacetic anhydride (PFAA) in the presence of ethylene.Reaction products up to dodecanes were identified and measured under various experimental conditions, i.e. at different ethylene concentrations, / ratios, reaction temperatures and incident light intensities.Disproportionation/combination ratios were obtained for the n-propyl, n-pentyl and s-heptyl free radicals.The rates of addition of the C3. and C5. radicals were studied at 300 and 362 K.The rate coefficient ratios kaddition/kcombination1/2 of (4.04+/-0.69)E-3 and (2.72+/-0.66)E-3 dm3/2 mol-1/2 s-1/2 were determined at room temperature for the n-propyl and n-pentyl radicals, respectively.The activation energies obtained were 27.8 kJ mol-1 for C3. addition and 26.8 kJ mol-1 for C5. addition.Isomerisation of the n-heptyl radical by 1,5-hydrogen shift was observed to occur and the isomerization rate coefficient relative to that of C7. self-combination, kisomeriz/kcomb1/2=(5.8+/-1.0)E-5 mol1/2 dm-3/2 s-1/2, was determined at room temperature.The kinetic results for addition and isomerization reactions are discussed in the light of available literature data.
