4630-45-9Relevant articles and documents
Homolytic dissociation of 1-substituted cyclohexa-2,5-diene-1-carboxylic acids: An EPR spectroscopic study of chain propagation
Jackson, Leon V.,Walton, John C.
, p. 1758 - 1764 (2007/10/03)
Hydrogen abstraction from 1-substituted cyclohexa-2,5-diene-1-carboxylic acids containing linear, branched and cyclic alkyl substituents, as well as allyl, propargyl (prop-2-ynyl), cyanomethyl and benzyl substituents, has been studied by EPR spectroscopy. For each carboxylic acid, EPR spectra of the corresponding cyclohexadienyl radicals were observed at lower temperatures, followed by spectra due to ejected carbon-centred radicals at higher temperatures. Rate constants, for release of the carbon-centred radicals from the cyclohexadienyl radicals, were determined from radical concentration measurements for the above range of substituents. The rate of cyclohexadienyl radical dissociation increased with branching in the 1-alkyl substituent and with electron delocalisation in the ejected carbon-centred radical; 3,5-and 2,6-dimethyl-substitution of the cyclohexadienyl ring led to reductions in the dissociation rate constants. Rate data for abstraction of bisallylic hydrogens from the cyclohexadienyl acids were also obtained for ethyl, n-propyl and isopropyl radicals. These results indicated a sharp drop in the rate of hydrogen abstraction as the degree of branching in the attacking radical increased. Small decreases in the hydrogen abstraction rate constants were observed for cyclohexadienes containing CO2R substituents.
Heats of Formation of Radicals and Molecules by a Photoacoustic Technique
Burkey, T. J.,Majewski, M.,Griller, D.
, p. 2218 - 2221 (2007/10/02)
A photoacoustic technique was used to measure heats of free radical reactions.To illustrate the method, bond dissociation energies were measured for the Sn-H bond in n-Bu3SnH, for the C3-H bond in 1,4-cyclohexadiene, and for the C2-H bond in diethyl ether.Heats of formation of t-BuOPPh3 and t-BuOP(Bu-n)2 were determined, and the method was also used to measure quantum yields for the photolysis of di-tert-butyl peroxide and diphenyl disulfide.
A Direct Study of the Reactions of CH2 (3B1)-Radicals with Selected Hydrocarbons in the Temperature Range 296 K
Dobe, S.,Boehland, T.,Temps, F.,Wagner, H. Gg.
, p. 432 - 441 (2007/10/02)
The kinetics of the reactions of CH2 (3B1)-radicals with five selected organic compounds has been studied in an isothermal discharge flow system in the temperature range 296 .Two basic reaction mechanisms, either direct H-atom abstarction by 3CH2 or thermal excitation of 3CH2 to the low lying 1A1 state followed by consecutive reactions of 1CH2, are of importance.For acetaldehyde, isobutane, and propane direct H-atom abstraction by 3CH2 predominates.After separation of the small contribution attributed to the singlet reaction the following rate constants for the reactions of CH2 (3B1) with acetaldehyde, isobutane, and propane are obtained: .Presuming the reactions of 1CH2 with hydrocarbons are fast the thermal excitation mechanism dominates the reaction system in the cases of methane and ethane.The activation energy of EA(CH4) = 40 +/- 8 kJ/mol measured for methane is concluded to be determined by the singlet-triplet energy splitting in CH2. - Keywords: Chemical Kinetics / Elementary Reactions / Laser Magnetic Resonance / Methylene / Radicals
