15157-95-6Relevant articles and documents
Observation of the 3s 2A1 Rydberg States of Allyl and 2-Methylallyl Radicals with Multiphoton Ionization Spectroscopy
Hudgens, Jeffrey W.,Dulcey, C.S.
, p. 1505 - 1509 (1985)
Previously unreported bands of allyl, allyl-d5, and 2-methylallyl radicals have been detected by mass-resolved, resonance-enhanced multiphoton ionization spectrometry.Focused laser light between 480 and 535 nm induced two-photon absorptions preparing the 3s 2A1 Rydberg states of the radicals.Absorption of two additioal photons ionized the excited radicals.These electronic states of allyl and 2-methylallyl radicals lie at 40085 and 38369 cm-1, respectively.No subsequent fragmentation of the molecular ions was observed.
A shock tube, laser-schlieren study of the pyrolysis of isobutene: Relaxation, incubation, and dissociation rates
Santhanam,Kiefer,Tranter,Srinivasan
, p. 381 - 390 (2003)
Dissociation, vibrational relaxation, and unimolecular incubation have all been observed in shock waves in isobutene with the laser-schlieren technique. Experiments covered a wide range of high-temperature conditions: 900-2300 K, and post-incident shock pressures from 7 to 400 torr in 2, 5, and 10% mixtures with krypton. The surprising observation is that of vibrational relaxation, well resolved over the full temperature range. The resolved process is completely exponential, with relaxation times in the range 20-120 ns atm. Relaxation and dissociation are clearly separated for T > 1850 K, with estimated incubation times near 200 ns atm. Incubation is essential for modeling of the very low-pressure decomposition. Modeling of gradients with a chain mechanism initiated by CH fission produces an excellent fit and accurate dissociation rates that show severe falloff. A restricted-rotor, Gorin-model RRKM analysis fits these rates quite well with the known bond-energy as barrier and 〈ΔE〉down = 680 cm-1. The extrapolated k∞ is log k∞ (s-1) = 19.187-0.865 log T -87.337 (kcal/mol)/RT, in good agreement with previous work.
Spectral image analysis for the absorption bands of the β-methallyl free radical in the vapor phase
Bayrakceken, Fuat,Telatar, Ziya,Ari, Fikret,Bayrak, Aykut B.
, p. 1276 - 1280 (2007)
The radicals formed in the flash photolysis of 2-methylbut-1-ene and subsequent reactions have been investigated by kinetic spectroscopy and gas liquid chromatography. Less than 10% of photo products are formed by a molecular made of fission of the excited olefin, and of the radical modes the relative probabilities of band fission, β(C{single bond}H):β(C{single bond}H):α(C{single bond}C) are 13:1.37:1. The extinction coefficients of β-methallyl radical measured experimentally for all the absorption bands. The decay of the β-methallyl radical was second order. The rate constant for the β-methallyl radical recombination experimentally measured was 2.6 ± 0.3 × 1010 l mol-1 s-1 at 295 ± 2 K. The spectrum image showing the absorption bands was examined by image processing techniques in order to improve the visual experience of each band by localizing to a specific region of interest. Experimental results illustrate how the exact location of absorption bands was clearly extracted from the spectral image and further improvements in the visual detection of absorption bands.
High-resolution discrete absorption spectrum of α-methallyl free radical in the vapor phase
Bayrakceken, Fuat,Telatar, Ziya,Ari, Fikret,Tuncyuerek, Lale,Karaaslan, Ipek,Yaman, Ali
, p. 143 - 146 (2006)
The α-methallyl free radical is formed in the flash photolysis of 3-methylbut-1-ene, and cis-pent-2-ene in the vapor phase, and then subsequent reactions have been investigated by kinetic spectroscopy and gas-liquid chromatography. The photolysis flash was of short duration and it was possible to follow the kinetics of the radicals' decay, which occurred predominantly by bimolecular recombination. The measured rate constant for the α-methallyl recombination was (3.5 ± 0.3) × 1010 mol-1 l s-1 at 295 ± 2 K. The absolute extinction coefficients of the α-methallyl radical are calculated from the optical densities of the absorption bands. Detailed analysis of related absorption bands and lifetime measurements in the original α-methallyl high-resolution discrete absorption spectrum image were also carried out by image processing techniques.
The Heat of Formation of the Allyl and Methallyl Radical
Roth, Wolfgang R.,Bauer, Frank,Beitat, Arndt,Ebbrecht, Thomas,Wuestefeld, Michael
, p. 1453 - 1460 (2007/10/02)
The decomposition of 1,5-hexadiene (1), 2-methyl-1,5-hexadiene (7), and 2,5-dimethyl-1,5-hexadiene into allyl- (2) and methallyl radicals (6) was studied by means of the shoke tube technique with and without oxygen as scavenger.From these data and from the temperature dependence of the equilibria 1 2 and 5 6, measured between 600 and 800 deg C, the heat of formation of the allyl (2) and methallyl radical (6) as well as the activation parameters for the recombination and disproportionation of these radicals have been deduced.
An E.S.R. study of radical cation cyclization in the radiolytic oxidation of but-3-en-1-ol solutions in freon matrices
Dai, Sheng,Wang, Jih Tzong,Williams, Ffrancon
, p. 1063 - 1064 (2007/10/02)
The radiolytic oxidation of but-3-en-1-ol in halogenoethane matrices produces e.s.r. signals from both the protonated tetrahydrofuran-3-yl radical and the allyl radical; the former species is readily attributable to the nucleophilic endo cyclization of radical cations generated from unassociated solute molecules whilst the allyl radical is thought to originate from the fragmentation of the alkoxyl radical produced from radical cations generated within solute clusters.
Formation of Gas-Phase Methylallyl Radicals during the Oxydation of 1-Butene and Isobutylene over Bismuth Oxide
Driscoll, Daniel J.,Martir, Wilson,Lunsford, Jack H.
, p. 3585 - 3588 (2007/10/02)
Using a matrix isolation-electron spin resonance (MIESR) technique it has been shown that Bi2O3 is capable of generating gas-phase 1-methylallyl and 2-methylallyl radicals from 1-butene and isobutylene, respectively.Previous results had suggested that the rate of surface-generated gas-phase radical formation over this material was governed by C-H bond strength differences only.These new results, however, indicate that other factors such as the availability of the abstractable hydrogen atoms and the reaction stereochemistry also may be important in determining the amount of gas-phase radicals produced.
TRAPPING OF ALLYLIC RADICALS FROM THE GAS PHASE PYROLYSIS IN THE ADAMANTANE MATRIX - ISOTROPIC ESR SPECTRA AT 77 K
Mach, Karel,Novakova, Jana,Dolejsek, Zdenek
, p. 1325 - 1333 (2007/10/02)
A simple device has been developed and tested for trapping radicals from the gas phase onto a cold finger kept at 77 K.The yields of allylic radicals obtained by pyrolysis of biallyl hydrocarbons were studied by ESR spectroscopy in dependence on the temperature and pressure of pyrolysis, both in the absence and presence of adamantane.The co-deposition of the radicals with adamantane increased considerably the radical yields and afforded isotropic ESR spectra of allyl radicals (ΔHmin = 0.21 mT) even at 77 K.The adamantane matrix formed from the gas phase appearedto be less rigid than the crystalline one, as the allylic radicals decayed already at 160-177 K.Yields of the trapped allyl radicals were also compared with the radical yields measured by mass spectrometry using analogous pyrolytic device.
Detection of Gas-Phase Organic Radicals Formed in Gas-Surface Reactions by Photoelectron Spectroscopy: Abstraction of Allylic Hydrogen by Bismuth Oxide
Schultz, Jocelyn C.,Beauchamp, J. L.
, p. 3587 - 3589 (2007/10/02)
Photoelectron spectroscopy has been used to detect gas-phase organic radicals as well as stable products formed in low-pressure gas-surface reactions.The products were sampled directly after exiting the catalyst bed.Allylic hydrogen abstraction by Bi2O3 at 760 degC forms gas-phase allyl and 2-methylallyl radicals from propylene and isobutylene, respectively, in the presence of oxygen.CO2 and H2O are the other observed products of alkene oxidation over Bi2O3.The product distributions and the 2-methylallyl radical yields as a function of oxygen pressure and Bi2O3 temperature are discussed.
