1605-73-8Relevant articles and documents
Studies of Free Radicals at High Pressures. 2. Kinetics for a Variety of Reactions
Marriott, P. R.,Griller, D.
, p. 1521 - 1525 (1981)
Kinetic EPR studies of a variety of free-radical reactions have been carried out at high pressures.Volumes of activation were measured for the β-scission reactions of di-tert-butyliminyl (3.0 +/- 1.0 cm3 mol-1) and triethoxy-tert-butoxyphosphoranyl (0.2 +/- 1.9 cm3 mol -1), for self-reaction of di-tert-butyliminyl (-18.0 +/- 5.3 cm3 mol-1), and for the rearrangements of 2,4,6-tri-tert-butylphenyl (5.3 +/- 1.7 cm3 mol -1) and 2,4,6-tris(perdeuterio-tert-butyl)phenyl (-1.2 +/- 2.0 cm3 mol-1).These measurements improve the descriptions of the transition states for the variuos reactions and in the case of the phenyl rearrangements provide supporting evidence for a mechanism involving quantum mechanical tunnelling.
Laser Flash Photolysis-Electron Spin Resonance Kinetic Studies of Homolytic Reactions in Solution
Baban, Jehan A.,Goddard, Jeffrey P.,Roberts, Brian P.
, p. 1269 - 1274 (1986)
Laser flash photolytic (308 nm) generation coupled with time-resolved e.s.r. spectroscopic detection of radical intermediates has been used to obtained absolute rate coefficients and activation parameters for a number of uni- and bi-molecular homolytic reactions in solution.The results accord well with ButOCO -> But + CO2 (a) (EtO)3POBut -> But + (EtO)3PO (B) ButO + cyclo-C5H10 -> cyclo-C5H9 + ButOH (C) ButO + ButOMe -> ButOCH2 + ButOH (D) Me3SiO + cyclo-C5H10 -> cyclo-C5H9 + Me3SiOH (E) Me3SiO + ButOMe -> ButOCH2 + Me3SiOH (F) those obtained previously for some of these reactions using other techniques.The data for reaction (C) are in excellent agreement with those obtained by laser flash photolysis coupled with optical detection of transients, but differ markedly from results obtained previously by a flash photolysis/e.s.r. technique.The kinetic results for the hydrogen transfers (E) and (F) represent the first absolute rate data for reactions of trialkylsiloxyl radicals.The trimethylsiloxyl radical is more reactive in hydrogen abstraction and also more electrophilic than ButO; these differences are attributable to the ?-acceptor properties of the Me3Si group.
Time-Resolved REMPI Detection of Methyl Radicals Generated in Laser-Induced Unimolecular Reactions
Froechtenicht, Ralf,Hartmann, Matthias
, p. 16290 - 16295 (1995)
The specific rate constants for the photofragmentation of four substituted benzene molecules (ethylbenzene, tert-butylbenzene, toluene, benotrifluoride) following pulsed laser excitation at λ=193 nm were measured in a molecular beam experiment by monitoring the change of the intensity of the nascent products as a function of time delay between excitation and detection laser pulses.In the case of toluene (C6H5CH3), ethylbenzene (C6H5CH2CH3), and tert-butylbenzene (C6H5C(CH3)3) a (3+1)REMPI process a Λ=450.8 nm was used to ionize the CH3 products, which were detected in a time-of-flight mass spectrometer.Following dissociation of benzotrifluoride (C6H5CF3) the trifluormethyl radical CF3 was detected at λ=455 nm.The measured specific rate constants can be modeled satisfactorily by using the SACM (statistic adiabatic channel model) statistical theory.
Thermolysis of 3,3,5,5-tetramethyl-1,2,4-trithiolane 1-oxide: First matrix isolation of the HOSS· radical
Reisenauer, Hans Peter,Mloston, Grzegorz,Romanski, Jaroslaw,Schreiner, Peter R.
scheme or table, p. 3408 - 3415 (2012/09/11)
Flash vacuum pyrolysis of 3,3,5,5-tetramethyl-1,2,4-trithiolane 1-oxide performed at 700 °C yields the 1-oxatrisulfan-3-yl radical (HOSS ·) along with disulfur monoxide (S2O) and diisopropyl sulfide, which were isolated in argon matrices at 10 K. Upon irradiation with UV light, the 1-oxatrisulfan-3-yl radical undergoes isomerization to the 1-oxatrisulfan-1-yl radical (HSSO·). Both radicals were identified by comparison of their computed and experimental IR and UV/Vis spectra. In addition, density functional theory (DFT) computations offer a plausible explanation of the most likely reaction mechanism, suggesting that the initial step is a 1,3-H shift with simultaneous ring opening. A 1-oxatrisulfane derivative formed thereby undergoes fragmentations via a radical and a competitive concerted pathway leading to the observed final products. The same mechanism also governs the thermal fragmentation of di-tert-butyl disulfide S-oxide. Its pyrolysis at 700 °C affords an analogous set of products, including the 1-oxatrisulfan-3-yl radical (HOSS·) as the key intermediate. 3,3,5,5-Tetramethyl-1,2,4-trithiolane 1-oxide was pyrolyzed in vacuo (FVP) yielding the 1-oxotrisulfan-1-yl radical, which was isolated in an Ar matrix at 10 K and subsequently characterized by spectroscopic methods (IR and UV/Vis). The same radical was obtained after vacuum pyrolysis of di-tert-butyl disulfide S-oxide.
Tin-free radical alkoxyamine addition and isomerization reactions by using the persistent radical effect: Variation of the alkoxyamine structure
Molawi, Kian,Schulte, Tobias,Siegenthaler, Kai Oliver,Wetter, Christian,Studer, Armido
, p. 2335 - 2350 (2007/10/03)
Various C-centered radicals can efficiently be generated through thermal C-O-bond homolysis of alkoxyamines. This method is used to perform environmentally benign radical cyclization and intermolecular addition reactions. These alkoxyamine isomerizations and intermolecular carboaminoxylations are mediated by the persistent radical effect (PRE). In the paper, the effect of the variation of the alkoxyamine structure - in particular steric effects in the nitroxide moiety - on the outcome of the PRE mediated radical reactions will be discussed. Fourteen different nitroxides were used in the studies. It will be shown that reaction times can be shortened about 100 times upon careful tuning of the alkoxyamine structure. Activation energies for the C-O-bond homolysis of the various alkoxyamines are provided. The kinetic data are used to explain the reaction outcome of the PRE-mediated processes.
