2417-82-5Relevant articles and documents
The Reactions of the Cyclic Hydrocarbon Radicals c-C3H5, c-C5H9, and c-C6H11 with O Atoms in the Gas Phase
Heinemann-Fiedler, P.,Hoyermann, K.,Rohde, G.
, p. 1400 - 1404 (2007/10/02)
The production of the cyclic hydrocarbon radicals c-C3H5, c-C5H9, and c-C6H11 by the reactions of c-C3H6, c-C5H10, and c-C6H12 with F atoms and the reactions of the cyclic hydrocarbon radicals with O atoms were studied at low pressure (around 1 mbar) and low temperature (290-300 K) using the discharge flow method.Stable and labile species were detected by mass spectrometry combined with molecular beam sampling.The rate constants of the reactions c-C3H5 + O (4), c-C5H9 + O (5), and c-C6H11 + O (6) were determined: k4 = 1.4*1014, k5 = 1.7*1014, k6 = 1.4*1014 cm3/mol*s.One main reaction route is interpretated by the formation of a highly excited adduct, decomposing to H + oxygen containing ring products; at high strain energy (reaction (4)) total ring cleavage, at low strain energy (reaction (6)) partial ring cleavage was observed.A second reaction route leads to OH + alkene.The rate constant for the reaction F + c-C6H12 (3) was found as k3 = 5.7*1013 cm3/mol*s.
Application of multi-photon ionization mass spectrometry to the study of the reactions O + C2H4, F + C3H6, F + c-C3H6, F + CH3OH, H + CH2OH and O + CH3O
Heinemann-Fiedler,Hoyermann
, p. 1472 - 1477 (2007/10/02)
The experimental arrangement of a time-of-flight mass spectrometer with multi-photon ionization and electron impact ionization is described. This set up was combined with a discharge flow reactor and a molecular beam sampling device. The detection of the radicals CH3, C3H5, CH2OH and their deuterated analogs by the wave-length selective multi-photon ionization allowed the identification of primary products of elementary reactions in the gas-phase (around 1 mbar).
An Electron Spin Resonance Investigation of Free Radicals with Oxigen- and Sulphur-containing Substituents
Beckwith, Athelstan L. J.,Brumby, Steven
, p. 1801 - 1808 (2007/10/02)
Electron spin resonance (e.s.r.) spectra have been recorded during the photolysis of di-t-butyl peroxide in the presence of a number of organic substrates with oxigen- and sulphur-containing functional groups.By hydrogen-atom abstraction, many of the substrates yield more than one species of free radical, the relative concentrations of which have been estimated.These relative concentrations are influenced by the electrophilic character of the t-butoxyl radical, and by the stabilities of the radical generated.Bis(methylthio)methane (2) gives rise to tris(methylthio)methyl radicals (5a), in addition to the two species expected by direct abstraction.Tris(methylthio)methane (5) gives rise to tris(methylthio)methyl radicals (5a) only, which from the measured α(13)C hyperfine splitting constant, appear to be approximately planar.Several of the substrates used give rise to captodative free radicals.The data indicate that alkylcarbonyl groups are more effective than the methoxycarbonyl group in the capto role.The acyclic captodative radicals all exist in two distinct conformations, the likely geometries of which are discussed.Observations on two cyclic radicals suggest that relatively small deviations from a suitable planar conformation can significantly diminish the importance of the captodative effect.
Absolute Rate Constants for the Reaction of Triethylsilyl Radicals with Organic Halides
Chatgilialoglu, C.,Ingold, K. U.,Scaiano, J. C.
, p. 5123 - 5127 (2007/10/02)
The absolute rate constants for the reactions of Et3Si. radicals with a number of organic halides have been measured in solution by using laser flash photolysis techniques.The reactivities cover a wide range; e.g., the rate constants at ca. 300 K are 4.3 * 109, 1.1 * 108, 2.5 * 106, and 5 M-1 s-1 for CH3CH2I, C6H5Br, (CH3)3CCl, and C6H5CH2F, respectively.Arrhenius parameters were determined for a few representative substrates.Thus, for CCl4, Ea = (0.78 +/- 0.24) kcal/mol and log (A/M-1 s-1) = 10.2 +/- 0.2, data which can be combined with relative rates from the literature to yield absolute rate constants for some additional substrates.Comparison of the Arrhenius parameters for halogen abstraction from several substrates suggests the involvment of charge-transfer interactions in some of these reactions.Such rate-enhancing interactions can have a greater influence on the preexponential factor than on the activation energy.An explanation for this phenomenon is advanced.Combination of our rate constants with data from literature also allows evaluation of the rates of inversion at the silicon center in triorganosilyl radicals as being in the range (3-12) * 109 s-1 at temperatures from 0 to 80 deg C which implies that a considerable activation barrier is involved in such process.
