2025-56-1Relevant articles and documents
Localization of Excitation Energy in Chemically Activated Systems. 3-Ethyl-2-methyl-2-pentyl Radicals
Flowers, M. C.,Rabinovitch, B. S.
, p. 563 - 565 (1985)
Chemically activated 3-ethyl-2-methyl-2-pentyl radicals were produced at 300 K by H-atom addition to 3-ethyl-2-methyl-2-pentene at hydrogen gas pressures of 15 to 10800 torr.These radicals can decompose to 2-methyl-2-pentene and an ethyl radical.The initially produced radical has a nonrandom energy distribution.Our observations help to clarify the size of the initially excited subset of vibrational modes; remaining uncertainty concerns the total number of internal rotational degrees of freedom to be included.An analogy exists to single photon vibrational excitation studies.
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McCauley,Schuler
, p. 4008,4009 (1957)
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Rate Coefficients of C2H with C2H4, C2H6, and H2 from 150 to 359 K
Opansky, Brian J.,Leone, Stephen R.
, p. 19904 - 19910 (1996)
Rate coefficients for the reactions C2H with C2H4, C2H6, and H2 are measured over the temperature range 150-359 K using transient infrared laser absorption spectroscopy.The ethynyl radical is formed by photolysis of C2H2 with a pulsed excimer laser at 193 nm, and its transient absorption is monitored with a color center laser on the Q11(9) line of the Α2Π-Χ2Σ transition at 3593.68 cm-1.Over the experimental temperature range 150-359 K the rate constants of C2H with C2H4, C2H6, and H2 can be fit to the Arrhenius expressions kC2H4 = (7.8 +/- 0.6)E-11 exp, kC2H6 = (3.5 +/- 0.3) E-11 exp, and kH2 = (1.2 +/- 0.3)E-11 exp/T cm3 molecule-1 s-1, respectively.The data for C2H with C2H4 and C2H6 indicate a negligible activation energy to product formation shown by the mild negative temperature dependence of both reactions.When the H2 data are plotted together with the most recent high-temperature results from 295 to 854 K, a slight curvature is observed.The H2 data can be fit to the non-Arrhenius form kH2 = 9.2E-18 T2.17+/-0.50 exp cm3 molecule-1 s-1.The curvature in the Arrhenius plot is discussed in terms of both quantum mechanical tunneling of the H atom from H2 to the C2H radical and bending mode contributions to the partition function.
A Shock Study of Methyl-Methyl Reactions between 1200 and 2400 K
Davidson, D. F.,Rosa, M. D. Di,Chang, E. J.,Hanson, R. K.,Bowman, C. T.
, p. 1179 - 1196 (1995)
The methyl-methyl reaction was studied in a shock tube using uv narrowline laser absorption to measure time-varying concentration profiles of CH3.Methyl radicals were rapidly formed initially by pyrolysis of various precursors, azomethane, ethane, or methyl iodide, dilute in argon.The contributions of the various product channels, C2H6, C2H5 + H, C2H4 + H2, and CH2 + CH4, were examined by varying reactant mixtures and temperature.The measured rate coefficients for recombination to C2H6 between 1200 and 1800 K are accurately fit using the unimolecular rate coefficients reported by Wagner and Wardlaw (1988).The rate coefficient for the C2H5 + H channel was found to be 2.4 (+/- 0.5) x 1013 exp(-6480/T) 3/mol-s> between 1570 and 1780 K, and is in agreement with the value reported by Frank and Braun-Unkhoff (1988).No evidence of a contribution by the C2H4 + H2 channel was found in ethane/methane/argon mixtures, although methyl profiles the these mixtures should be particularly sensitive to this channel.An upper limit of approximately 1011 3/mol-s> over the range 1700 to 2200 K was inferred for the rate coefficient of the C2H4 + H2 channel.Between 1800 and 2200 K, methyl radicals are also rapidly removed by CH3 + --> 1CH2 + H2.In this temperature range, the reverse reaction was found to have a rate coefficient of 1.3 (+/- 0.3) x 1014 3/mol-s>, which is 1.8 times the room-temperature value.
Gas-Phase Reactions of FeO+ with Hydrocarbons
Jackson, T. C.,Jacobson, D. B.,Freiser, B. S.
, p. 1252 - 1257 (1984)
The reactions of FeO+ with linear alkanes, cyclic alkanes, and branched alkanes are presented.In general from the reactions observed, it appears that FeO+ is more reactive toward alkanes than Fe+ which is due mainly to the
Unimolecular and Bimolecular Reactions of the β-Distonic Ion CH3CH2OH+CH2CH2. : An Experimental and Theoretical Study
Brenner, Valeerie,Milliet, Arielle,Mourgues, Philippe,Ohanessian, Gilles,Audier, Henri-Edouard
, p. 10837 - 10846 (1995)
In the gas phase, the unimolecular reaction of the metastable β-distonic ion 1, CH3CH2OH+CH2CH2., yields a CH3CHOH+ fragment ion.Experiments using isotopomers of 1 and ab initio calculations show that two pathways lead to its dissociation: (i) a 1,4-H migration leading to the α-distonic ion 2, CH3CH.OH+CH2-CH3 with subsequent elimination of C2H5.; (ii) a H transfer within a .+ intermediate complex 3 followed by loss of C2H5..Two isomerization processes can occur prior to dissociation: a rapid permutation of the CH2 groups in the radical chain and a reversible 1,5-H migration.The calculated transition state for 1,5-H migration and those arising on the fragmentation pathways are close in energy and correspond to relatively reactions of 1 with several neutral molecules are shown to be accompanied by the same 1,4- and 1,5-H migrations.The structures of the different isomeric ions thus formed were characterized by their specific ion-molecule reactions.The energy required for the various processes observed arises from the stabilization in the initial encounter complexes between 1 and each neutral molecule.
Using toluates as simple and versatile radical precursors
Lam, Kevin,Marko, Istvan E.
scheme or table, p. 2773 - 2776 (2009/05/30)
(Chemical Equation Presented) The viability of the toluate moiety as a radical precursor has been examined by studying deoxygenation and cyclization reactions.
Ion-molecule reactions of state selected HCl+ ions with carbon dioxide and ethene
Malow, Marcus,Brembs, Klaus,Weitzel, Karl-Michael
, p. 737 - 747 (2007/10/03)
The ion-molecule reactions of state selected HCl+ (ν, N) ions with carbon dioxide and ethene have been investigated. For the reaction HCl+ +CO2 proton transfer leading to the HOCO+ ion is the only reaction channel observed. For the reaction HCl+ + C2H4 very efficient charge transfer (leading to C2H4+ + HCl) dominates at low particle densities. At higher densities consecutive reactions leading e.g. to C2H2+, C2H3+, and C2H5+ take over. A kinetic model is presented which allows to derive rate constants for the relevant elementary reactions. Under the current experimental conditions the rate constants are found to be independent of the rotational angular momentum N of the HCl+ ions. by Oldenbourg Wissenschaftsverlag, Muenchen.
