3170-80-7Relevant academic research and scientific papers
Exploratory Study of the Intermolecular Reactivity of Excited Diphenylmethyl Radicals
Scaiano, J. C.,Tanner, M.,Weir, D.
, p. 4396 - 4403 (1985)
A series of intermolecular reactions of excited diphenylmethyl radicals has been examined with laser flash photolysis techniques.The radicals, Ph2CH(.), were generated by 308-nm photodecomposition of 1,1,3,3-tetraphenylacetone or diphenyldiazomethane.In the latter system the radicals result from reaction of diphenylcarbene with hydrogen-donor solvents.The radicals were then excited with the 337-nm pulses from a nitrogen laser, leading to the formation of the readily detectable excited state of the radical, Ph2CH(.) (λmax 355 nm).The excited radical is an excellent electron donor, reacting with methyl viologen with kq=1.3*1010 M-1s-1 in wet acetonitrile and leading to the formation of methyl viologen radical cation.Ph2CH(.) is readily quenched by amines, but no evidence for full electron transfer could be obtained, e.g., for triethylamine kq = 5.2*108 M-1 s-1 in cyclohexane.The excited radical is 14 times more reactive toward oxygen than its ground state, but the process seems to involve a different mechanism, probably leading to singlet oxygen generation.Halogenated substrated react readily with Ph2CH(.); for example, for CCl4 kq = 1.6*108 M-1 s-1 and leads to Ph2CHCl in a process that is presumed to involve charge transfer.Excited diphenylmethyl is not a good hydrogen abstractor in spite of the fact that its hydrogen abstraction reactions would be more exothermic than those of phenyl radicals.
Atmospheric Chemistry of Pentachloroethane (CCl3CCl2H): Absorption Spectra of CCl3CCl2 and CCl3CCl2O2 Radicals, Kinetics of the CCl3CCl2O2 + NO Reaction, and Fate of the CCl3CCl2O Radical
Moegelberg, Trine E.,Sehested, Jens,Nielsen, Ole J.,Wallington, Timothy J.
, p. 16932 - 16938 (1995)
The absorption spectra of CCl3CCl2 and CCl3CCl2O2 radicals and the rate constant for the reaction of CCl3CCl2O2 radicals with NO were measured at 296 +/- 2 K using a pulse radiolysis technique.The absorption spectra were measured over the wavelength range 220-400 nm.At 230 nm ?(CCl3CCl2) = (271 +/- 84)E-20 cm2 molecule-1, and at 240 nm ?(CCl3CCl2O2) = (145 +/- 21)E-20 cm2 molecule-1.The reaction of F atoms with CCl3CCl2H was determined to have a rate constant of (2.3 +/- 1.6)E-12 cm3 molecule-1 s-1.The reaction of CCl3CCl2O2 with NO proceeds with a rate constant of (6.2 +/- 1.6)E-12 cm3 molecule-1 s-1.This reaction gives NO2 and CCl3CCl2O radicals.In the atmosphere, 85percent of the CCl3CCl2O radicals eliminate a Cl atom to give CCl3C(O)Cl, and the remaining 15percent decompose via C-C bond scission to give CCl3 radicals and COCl2.As part of the present work, relative rate techniques were used to measure rate constants at 296 +/- 2 K for the reactions of Cl and F atoms with CCl3CCl2H of (5.2 +/- 0.7)E-14 and (2.0 +/- 0.5)E-12 cm3 molecule-1 s-1, respectively.
RADIOLYSIS OF TETRACHLOROMETHANE
Symons, Martyn C. R.,Albano, Emanuele,Slater, Trevor F.,Tomasi, Aldo
, p. 2205 - 2214 (1982)
Electron spin resonance studies of tetrachloromethane after exposure to (60)Coγ-rays at 77 K reveal the formation of .CCl3 and CCl4.+ radicals.On warming in the presence of spin-traps, or on irradiating fluid solutions, nitroxide radical adducts have been detected that are characteristic of .CCl3 and chlorine atom adducts.In the light of this evidence and that of other investigators a mechanism for the radiolysis of tetrachloromethane is postulated.In the presence of oxygen, .CCl3 radicals are converted into Cl3COO. radicals.The use of spin-traps to detect these radicals is described and evaluated.
Kinetics of reactions of CN with chlorinated methanes
Samant, Vaishali,Hershberger, John F.
experimental part, p. 64 - 67 (2009/02/04)
The kinetics of reactions of CN with the chlorinated methanes CH3Cl, CH2Cl2, CHCl3 and CCl4 were investigated over the temperature range 298-573 K, using laser induced fluorescence (LIF) spectroscopy. At 298 K, rate constants of 9.0 ± 0.3 × 10-13, 8.8 ± 0.4 × 10-13, 9.0 ± 0.5 × 10-13 and 4.3 ± 0.6 × 10-13 cm3 molecule-1 s-1 were measured, respectively. A small positive temperature dependence was observed, as well as kinetic isotope effects of kH/kD ～ 2.14-2.25. These data along with product detection experiments strongly suggest that hydrogen abstraction dominates these reactions.
Halogen abstraction reaction between aminoalkyl radicals and alkyl halides: Unusual high rate constants
Lalevée,Allonas,Fouassier
scheme or table, p. 415 - 418 (2009/02/02)
The very high reactivity of aminoalkyl radicals toward the halogen abstraction reaction is reported for the first time. Reaction rate constants with CCl4 and CBr4 are close to the diffusion limit: they are about 4-5 orders of magnitude higher than those previously determined for typical alkyl radicals. A better understanding of this unusual behavior is obtained using molecular orbitals (MO) calculations. The participation of polar effects is directly evidenced. This approach can be useful for the design of new reducing agents.
FTIR and computational studies of gas-phase hydrogen atom abstraction kinetics by t-butoxy radical
Li, Shuping,Fan, Wai Yip
, p. 276 - 280 (2007/10/03)
By using Fourier-Transform Infrared (FTIR) absorption spectroscopy, rate coefficients in the range of 10-16 to 10-14 cm3 molecule-1 s-1 have been determined for the hydrogen atom abstraction reactions of several substrates including halogenated organic compounds and amines by t-butoxy radical generated from the uv photolysis of t-butyl nitrite in the gas phase. Arrhenius parameters for selected reactions have been measured in the temperature range 299-318 K. Transition states and activation barriers for such reactions have been computed with the help of Gaussian 03 software and found to match very well with the experimental values.
Temperature dependence of the reactions of phenyl radicals with 1,1-diphenylethylene, carbon tetrachloride, and cyclohexene
Weldon, Dean,Holland, Stacey,Scaiano
, p. 8544 - 8546 (2007/10/03)
The reaction of phenyl radicals with 1,1-diphenylethylene (DPE), carbon tetrachloride, and cyclohexene has been examined over a range of temperatures using laser flash photolysis techniques. The activation energies are 0.71 ± 0.04, 3.53 ± 0.11 and 2.32 ± 0.33 kcal/mol, and the preexponential factors, expressed as log (A/M-1s-1), are 9.19 ± 0.03, 8.96 ± 0.09, and 9.02 ± 0.26, for DPE, CCl4, and c-C6H10, respectively. In particular the CCl4 data provide a much needed reference for competitive studies.
Thermal Decomposition of Carbon Tetrachloride
Michael, J. V.,Lim, K. P.,Kumaran, S. S.,Kiefer, J. H.
, p. 1914 - 1919 (2007/10/02)
The first rate measurements of the thermal dissociation of CCl4 are reported.Three detection techniques were used in monitoring the reaction rate for various dilutions over a wide temperature range: (i) ARAS of product Cl atoms in reflected shock waves using 3.2-6.4 ppm of CCl4 in Ar over 1084-1705 K and 150-908 Torr, (ii) decay of CCl4 by molecular absorption of O-atom resonance radiation in reflected shock waves using 48 - 173 ppm of CCl4 in Ar over 1192 - 1733 K and 219 - 855 Torr, and (iii) laser schlieren density gradients in incident shock waves using 0.5 and 2 percent CCl4 in Kr over 1470 - 2186 K and 90 - 660 Torr.The second-order rates from ARAS and molecular absorption measurements for the bond fission reaction CCl4 -> CCl3 + Cl are in complete agreement with the laser schlieren results where they overlap.The temperature and pressure dependence of these rates is well characterized by Gorin model RRKM calculations using a current Δ H00 = 67.71 kcal/mol for E0, derived from ΔfH0298 = 17.0 kcal/mol for CCl3.The low-pressure rate constant (k0) derived from this RRKM fit is log k0 (cm3/mol s)) = 54.980 - 10.624 log T - 74.796 (kcal/mol)/2.303RT.These low-pressure rates require unusually large βc corresponding to a down = 1200 cm-1.This may be a general feature of chlorocarbon dissociations.The ARAS data indicate that two Cl atoms are ultimately produced for each CCl4 that dissociates, with second Cl atom forming slower than the first.Here all measurements are consistent with a further dissociation of CCl3, CCl3 -> CCl2 + Cl, as the dominant source of secondary Cl-atom at a rate about 0.1 that of the primary fission.
Reaction of phenylchlorocarbene and diphenylcarbene with the carbon-chlorine bond: Kinetics and mechanisms
Jones, Michelle B.,Maloney, Vincent M.,Platz, Matthew S.
, p. 2163 - 2169 (2007/10/02)
The reactions of phenylchlorocarbene (PCC) and diphenylcarbene (DPC) with carbon-chlorine bonds were investigated by laser flash photolysis techniques, product studies, and electrochemical methods. The data with both carbenes are consistent with a polar chlorine atom transfer to form radical pairs. The PCC reaction can be thought of as an inner sphere electron transfer from the carbene to the carbon-halogen bond in which there is partial carbon-halogen bond formation in the transition state. The transition state is thought to involve a crossing between closed- and open-shell singlet surfaces. The data obtained in the reaction of DPC with chlorine donors resembles the data obtained with PCC but is more difficult to interpret because the multiplicity of the state reacting with the C-Cl bond is unclear.
Direct kinetic studies of SiH3 + SiH3, H, CCl4, SiD4, Si2H6, and C3H6 by tunable infrared diode laser spectroscopy
Loh, S. K.,Jasinski, J. M.
, p. 4914 - 4926 (2007/10/02)
Gas phase reactions of silyl radical, SiH3, are investigated at room temperature using tunable diode laser flash kinetic spectroscopy.Photolytic generation of silyl at 193 and 248 nm is demonstrated using several different precursor systems.The silyl recombination reaction, SiH3 + SiH3 -> Si2H6, is studied by quantitative measurement of SiH3 and attendant product densities.Analysis yields a refinement of the rate constant, krc = (7.9 +/- 2.9) * 10-11 cm3 molecule-1 s-1.By modeling silyl densities following photolysis of HCl in SiH4, bimolecular rate constants for H + SiH3 and H + SiH4 are determined to be (2 +/- 1) * 10-11 and (2.5 +/- 0.5) * 10-13 cm3 molecule-1 s-1, respectively.Reactions of SiH3 with SiD4, Si2H6, CCl4, and C3H6 (propylene) are studied under pseudo-first-order conditions.Derived upper limits to the rate constants show these reactions to be slow at room temperature.The data demonstrate the reactivity of silyl with open-shell (radical) species and the general inertness of silyl toward closed shell molecules.Under typical chemical vapor deposition conditions, SiH3 is, therefore, a kinetically long-lived species in the gas phase and consequently a potentially important film forming species under plasma and photochemical deposition conditions.
