2679-29-0Relevant academic research and scientific papers
FTIR and computational studies of gas-phase hydrogen atom abstraction kinetics by t-butoxy radical
Li, Shuping,Fan, Wai Yip
, p. 276 - 280 (2007/10/03)
By using Fourier-Transform Infrared (FTIR) absorption spectroscopy, rate coefficients in the range of 10-16 to 10-14 cm3 molecule-1 s-1 have been determined for the hydrogen atom abstraction reactions of several substrates including halogenated organic compounds and amines by t-butoxy radical generated from the uv photolysis of t-butyl nitrite in the gas phase. Arrhenius parameters for selected reactions have been measured in the temperature range 299-318 K. Transition states and activation barriers for such reactions have been computed with the help of Gaussian 03 software and found to match very well with the experimental values.
Exploitation of aldoxime esters as radical precursors in preparative and EPR spectroscopic roles
McCarroll, Andrew J.,Walton, John C.
, p. 2399 - 2409 (2007/10/03)
Photolyses of aldoxime esters, containing a considerable range of alkyl groups, lead to cleavage of their N-O bonds and formation of aryliminyl and alkyl radicals. The process was found to be favoured by 4-methoxyacetophenone as a photosensitiser and by methoxy substituents in the aryl rings. 4-Nitro- and pentafluoro-substitutions of the aryl rings were, on the other hand, deleterious. The intermediate iminyl radicals, together with primary, secondary and tertiary alkyl radicals were characterised by 9 GHz EPR spectroscopy. Cyclopropyl, CF3, and CCl3 radicals were probably also formed, but were too reactive for direct EPR spectroscopic detection. Photosensitised reaction of benzophenone oxime O-nonanoyl ester produced the diphenylmethaniminoxyl, as well as the expected n-octyl and iminyl radicals. This indicated that O-C bond scission accompanied O-N scission for this ketoxime ester. At higher temperatures the C-centred radicals added to the starting oxime esters to produce alkoxyaminyl radicals that were also spectroscopically detected in some cases. No evidence for abstraction of the iminyl hydrogen by tertbutoxyl radicals was obtained. Instead, the t-BuO radicals added to the C=N double bonds of the oxime esters. Similarly, chlorine abstraction from alkylbenzohydroximoyl chlorides by trimethyltin radicals did not take place. Preparative scale experiments with oxime esters containing suitably unsaturated alkyl groups showed that good yields of cyclised products could be obtained in the presence of the photosensitiser. This process constitutes a general method by which carboxylic acids or acid chlorides can be converted into alkyl radicals and hence to cyclised derivatives.
Reactions of Atomic Oxygen (3P) with Selected Alkanes
Miyoshi, Akira,Tsuchiya, Kentaro,Yamauchi, Noboru,Matsui, Hiroyuki
, p. 11452 - 11458 (2007/10/02)
Rate constants for the reactions of atomic oxygen (3P) with selected alkanes (C2-C6 straight chain alkanes, c-C6H12, neo-C5H12, and i-C4H10) have been determined directly by a laser photolysis-shock tube-atomic resonance absorption method at hi
ON THE REMOVAL OF METALLIC MIRRORS BY FREE RADICALS.
Rice,Tweedell
, p. 995 - 997 (2007/10/02)
Large radicals can be formed by passing chlorinated organic compounds at pressures of a few mm. , through a furnace containing a pellet of sodium and heated to 350-400 degree C. It is found that the only radicals that will remove metallic mirrors (of tellurium or antimony, etc. , previously deposited beyond the furnace) are those that can decompose into methyl or ethyl radicals plus an unsaturated molecule, without undergoing any transmigration of atoms. The authors also found, especially in the case of larger monochlorinated molecules, that there was some decomposition, approximately half, even in the absence of metallic sodium.
Kinetics of the Reactions between CH2(3B1)-Radicals and Saturated Hydrocarbons in the Temperature Range 296 K
Boehland, T.,Dobe, S.,Temps, F.,Wagner, H. Gg.
, p. 1110 - 1116 (2007/10/02)
The reaction between CH2-radicals in their ground electronic state (3B1) and n-hexane CH2() + n-C6H14 --> CH3 + C6H13 was studied in a discharge flow system with LMR detection of CH2.In the temperature regime 413 K 4 = 1E(13.22 +/- 0.20)*exp(-3380 +/- 240/T) cm3/mol s.The reaction proceeds both via direct H-atom abstraction by CH2() and via thermal excitation of CH2() to the low-lying singlet state (1A1) followed by fast consecutive reactions of CH2().The contributions due to thermal excitation and singlet reaction were evaluated for the present work as well as for a recent study of the reactions of CH2() with a series of other hydrocarbons.Corrected rate constants kT for the direct reactions of CH2() with the reactants HR = CH4 (1), C2H6 (2), C3H8 (3), n-C6H14 (4), i-C4H10 (5), and CH3CHO (6) in the temperature range 296 K 1T = 4.3E12*exp(-42 kJ mol-1/RT) cm3/mol s, k2T = 6.5E12*exp(-33.1 kJ mol-1/RT) cm3/mol s, k3T = 4.9E12*exp(-27.7 kJ mol-1/RT) cm3/mol s, k4T = 7.8E12*exp(-25.6kJ mol-1/RT) cm3/mol s, k5T = 2.5E12*exp(-22.5 kJ mol-1/RT) cm3/mol s, k6T = 1.7E12*exp(-14.7 kJ mol-1/RT) cm3/mol s.The activation energies for the reactions studied are described by an Evans Polanyi type relation.Arrhenius expressions are proposed for the rate constants of H-atom abstraction by CH2(3B1) from primary, secondary, tertiary, and aldehydic C-H bonds.The results are compared to the isoelectronic reactions of O(3P). - Keywords: Chemical Kinetics / Elementary Reactions / Radicals / Spectroscopy, Laser Magnetic Resonance
ESTIMATION DU RAPPORT KD/KC POUR DES RADICAUX ALKYLES EN PHASE SOLIDE
Tilman, P.,Tilquin, B.,Claes, P.
, p. 629 - 632 (2007/10/02)
Alkanes were γ-irradiated in the solid state at 77 K.Post-irradiation scavenging of trapped radicals by dissolving the irradiated alkanes in a propane-oxygen mixture lowers the dimer yields to an extend corresponding to the radical contribution to the dimer formation.From the reduction in the radiolytic yields and esr measurements of the trapped radical yields, values are obtained for the kd/kc disproportionation-combination rate constants ratio in solid state at different temperatures.These ratios are briefly discussed and are found to depend on temperature and quality of the radicals.The data are reported on Table III.
