Rate coefficient for the reaction of CCl3 radicals with ozone

The rate coefficient for the reaction of CCl₃ radicals with ozone has been measured at 303 ± 2 K. The CCl₃ radicals were generated by the pulsed laser photolysis of carbon tetrachloride at 193 nm. The time profile of CCl₃ concentration was monitored with a photoionization mass spectrometer. Addition of the O₃–O₂ mixture to this system caused a decay of the CCl₃ concentration because of the reactions of CCl₃ + O₃ → products (5) and CCl₃ + O₂ → products (4). The decay of signals from the CCl₃ radical was measured in the presence and absence of ozone. In the absence of ozone, the O₃–O₂ mixture was passed through a heated quartz tube to convert the ozone to molecular oxygen. Since the rate coefficient for the reaction of CCl₃ + O₂ could be determined separately, the absolute rate coefficient for reaction ( 5 ) was obtained from the competition among these reactions. The rate coefficient determined for reaction ( 5 ) was (8.6 ± 0.5) × 10^?13 cm³ molecule^?1 s^?1 and was also found to be independent of the total pressure (253–880 Pa of N₂). This result shows that the reaction of CCl₃ with O₃ cannot compete with its reaction with O₂ in the ozone layer. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 310–316, 2003     

Kinetics of the reactions of CCl3 with O and O2 and of CCl3O2 with NO at 295 K

The reactions of CCl₃ with O(³P) and O₂ and those of CCl₃O₂ with NO have been studied at 295 K using discharge flow methods with helium as the bath gas. The rate coefficient for the reaction of CCl₃ with O was found to be (4.2 ± 0.6) × 10^?11 cm³/s and that for CCl₃O₂ with NO was (18.6 ± 2.8) × 10^?12 cm³/s with both coefficients independent of [He]. For reaction between CCl₃ and O₂ the rate coefficient was found to increase from 1.51 7times; 10^?14 cm³/s to 7.88 × 10^?14 cm³/s as the [He] increased from 3.5 × 10¹⁶ cm^?3 to 2.7 × 10¹⁷ cm^?3. There was no evidence for a direct two-body reaction, and it is concluded that the only product of this reaction is CCl₃O₂. Examination of these results for CCl₃ + O₂ in terms of current simplified falloff treatment suggests that the high-pressure limit for this reaction is ～ 2.5 × 10^?12 cm³/s, which may be compared with a direct measurement of the high-pressure limit of 5 × 10^?12 cm³/s. A value of (5.8 ± 0.6) × 10^?31 cm⁶/s has been obtained for k₀, the coefficient in the low-pressure region. This value is compared with corresponding values found earlier for the (CH₃, O₂) and (CF₃, O₂) systems and with estimates based on unimolecular rate theory.     

Kinetics and mechanism of the thermal gas-phase reaction between trifluoromethylhypofluorite,CF3OF,and tetrachloroethene

The thermal gas-phase reaction of CF₃OF with CCl₂CCl₂ has been studied between 313.8 and 343.8 K. The initial pressure of CF₃OF was varied between 10.8 and 77.5 torr and that of CCl₂CCl₂ between 3.7 and 26.8 torr. CF₃OF was always present in excess, varying the initial ratio of CF₃OF to that of CCl₂CCl₂ from 1.3 to 10. Three products were formed: CF₃OCCl₂CCl₂F, CCl₂FCCl₂F, and CF₃O(CCl₂CCl₂) ₂OCF₃. The yields of CF₃OCCl₂CCl₂F were 98–99.5%, based on the sum of the products. The reaction was a homogeneous chain reaction not affected by the total pressure. In presence of O₂ the oxidation of CCl₂CCl₂ to CCl₃C(O)Cl and COCl₂ occurred. The proposed basic reaction steps are: generation of the radicals CF₃O˙ and CCl₂FCCl₂˙ (κ₁) in a biomolecular process between CF₃OF and CCl₂CCl₂, formation of the radical CF₃OCCl₂CCl₂˙ by addition of CF₃O˙ to CCl₂CCl₂, chain generation of CF₃O˙ by abstraction of fluorine atom from CF₃OF by CF₃OCCl₂CCl₂˙ (κ₄), and chain termination by recombination of the radicals CF₃OCCl₂CCl₂˙. The expressions obtained for the constants κ₁ and κ₄ are κ₁ = 3.16 ± 0.6 × 10⁷ exp(−15.2 ± 1.7 Kcal mol⁻¹/RT) dm³ mol⁻¹ s⁻¹, κ₄ = 3.7 ± 0.5 × 10⁹ exp(−6.0 ± 1.1 Kcal mol⁻¹/RT) dm³ mol⁻¹ s⁻¹. © 1996 John Wiley & Sons, Inc.     

Kinetics and mechanism for the oxidation of 1,1,1-trichloroethane

The reaction mechanisms for oxidation of CH₃CCl₂ and CCl₃CH₂ radicals, formed in the atmospheric degradation of CH₃CCl₃ have been elucidated. The primary oxidation products from these radicals are CH₃CClO and CCl₃CHO, respectively. Absolute rate constants for the reaction of hydroxyl radicals with CH₃CCl₃ have been measured in 1 atm of Argon at 359, 376, and 402 K using pulse radiolysis combined with UV kinetic spectroscopy giving ??(OH + CH₃CCl₃) = (5.4 ± 3) 10^?12 exp(?3570 ± 890/RT) cm³ molecule^?1 s^?1. A value of this rate constant of 1.3 × 10^?14 cm³ molecule^?1 s^?1 at 298 K was calculated using this Arrhenius expression. A relative rate technique was utilized to provide rate data for the OH + CH₃ CCl₃ reaction as well as the reaction of OH with the primary oxidation products. Values of the relative rate constants at 298 K are: ??(OH + CH₃CCl₃) = (1.09 ± 0.35) × 10^?14, ??(OH + CH₃CClO) = (0.91 ± 0.32) × 10^?14, ??(OH + CCl₃CHO) = (178 ± 31) × 10^?14, ??(OH + CCl₂O) < 0.1 × 10^?14; all in units of cm³ molecule^?1 s^?1. The effect of chlorine substitution on the reactivity of organic compounds towards OH radicals is discussed.     

Effect of the physical state on the scavenging of quasi-free electrons by a solute

The reactivity of carbon tetrachloride toward quasi-free electrons generated during the decay of ⁵⁷Co atoms in its alcohol solutions frozen at 80 K has been studied by Mössbauer emission spectroscopy. It has been found that an increase in CCl₄ concentration to 10 mol/L slightly affects the yield of ⁵⁷Fe²⁺ and ⁵⁷Fe³⁺ ions as ⁵⁷Co decay products. The inertness of CCl₄ has been interpreted as a consequence of a change of the energy state of quasi-free track electrons results from freezing the alcohol solution. This effect inhibits the dissociative attachment reaction of scavenging of track electrons and increases the ground-state energy of quasi-free electrons (on passing to the frozen matrix), thereby fundamentally altering the energy balance of the electron scavenging reaction in comparison with the liquid medium and, hence, decreasing the rate constant of electron scavenging by CCl₄.     

Rotating sector study of the gas phase photochlorination of 2,2-dichloro-1,1,1-trifluoroethane

The rate constant for the combination of 2,2-dichloro-1,1,1-trifluoroethyl radicals has been measured by applying the rotating sector technique to the gas phase photochlorination of 2,2-dichloro-1,1,1-trifluoroethane at 315°K. The observed value is 6.89 × 10¹² cc/mole.sec. This value is in excellent agreement with measurements by Wampler and Kuntz which yielded a temperature-independent value of 6.6 × 10¹² cc/mole.sec. The measurement by Wampler and Kuntz was determined from the photochemical system (CF₃CCl₃ + C-C₆H₁₂ + hν). The Arrhenius parameters for the reaction CF₃CCl₂· + Cl₂ → CF₃CCl₃ + Cl were found to be given by the expression log k₃ = 12.10 ? 5830/2.3RT (units in mole, cc, and sec). This is a relatively high activation energy for a chlorination reaction and makes the reaction ever slower than the chlorination of chloroform.     

Über Trichlorphosphazo-Verbindungen aus Nitrilen. III. Die Reaktion zwischen Acrylnitril und PCl3

On Trichlorophosphazo Compounds from Nitriles. III. The Reaction between Acrylonitrile and PCl₃. The reaction of PCl₃ with acrylonitrile at higher temperatures gives CH₂Cl? CCl₂? CCl₂? N? PCl₃ ( II ). On pyrolysis of (II), CH₂Cl? CCl₂? CN (IV) is form- ed. Treatment of (II) with SO, results in CHzCL? CCl₂? CCl?N-P(0)Cl₂ ( III ). At lower temperatures and/or in the presence of PCl₃, acrylonitrile reacts with PCl₃ to give the cis/ trans isomers VIa and VIb .     

The polymerizations of N-methyl-N-phenyl-2-aminoethyl methacrylate and 4-dimethylaminostyrene initiated with carboxylic acids

By using the copolymerizations of N-methyl-N-phenyl-2-aminoethyl methacrylate (I) and 4-dimethylaminostyrene (II) with styrene initiated with 2,2′-azoisobutyronitrile (AIBN) and with CCl₃COOH, the copolymerization parameters and Alfrey-Price copolymerization constants e and Q were determined for I and II. The only product of polymerizations initiated with CCl₃COOH and CH₃COOH in mixtures of II with vinyl monomers was a homopolymer of II. The order of homopolymerization of II in benzene initiated with CCl₃COOH at 50° was 0.99 with respect to [II] and 1.10 with respect to [CCl₃COOH]; the temperature dependence of homopolymerization in the range 25–40° was 63 ± 5 kJ mol^?1. The rate of homopolymerization of II in solution in C₆H₆ at 50° was virtually unaffected by inhibitors. In the polymerization initiated with carboxylic acids, the radical character of propagation centres was proved for I, but not for II.     

Thermal and Other Properties of New 4,4'-bipyridine-trichloroacetato Complexes of Mn(II), Ni(II) and Zn(II)

New mixed-ligand complexes of general formulae Mn(4-bpy)(CCl₃COO)₂⋅H₂O, Ni(4-bpy)₂(CCl³COO)₂⋅2H²O and Zn(4-bpy)₂(CCl₃COO)₂⋅2H²O (where 4-bpy=4,4’-bipyridine) were obtained and characterized. The IR spectra, conductivity measurements and other physical properties of these compounds were discussed. The central atoms M(II) form coordinate bonds with title ligands. The thermal behaviour of the synthesized complexes was studied in air. During heating the complexes decompose via different intermediate products to Mn₃O₄, NiO and ZnO; partial volatilization of ZnCl₂was observed. A coupled TG-MS system was used to the analysis of the principal volatile thermal decomposition products of Mn(II) and Ni(II) complexes. The principal volatile mass fragments correspond to: H₂O⁺, OH⁺, CO⁺ ₂, HCl⁺, Cl⁺ ₂, CCl⁺ and other. This revised version was published online in August 2006 with corrections to the Cover Date.     

Determination of the Rate Constant of the Reaction of CCl2 with HCl

The rate constant of the reaction between CCl₂ radicals and HCl was experimentally determined. The CCl₂ radicals were obtained by infrared multiphoton dissociation of CDCl₃. The time dependence of the CCl₂ radicals' concentration in the presence of HCl was determined by laser‐induced fluorescence. The experimental conditions allowed us to associate the decrease in the concentration of radicals to the self‐recombination reaction to form C₂Cl₄ and to the reaction with HCl to form CHCl₃. The rate constant for the self‐recombination reaction was determined to be in the high‐pressure regime. The value obtained at 300 K was (5.7 ± 0.1) × 10^?13 cm³ molecule^?1 s^?1, whereas the value of the rate constant measured for the reaction with HCl was (2.7 ± 0.1) × 10^?14 cm³ molecule^?1 s^?1.     

Molecular fragmentations: Part IV. The mass spectral fragmentation of carbon tetrachloride

MINDO/3 calculations have been made of the molecular structures and energies of seven isomeric forms of the molecular cation (CCl₄)⁺, of the mass spectral fragment pairs:

and also of a number of neutral fragment pairs. Reaction energy profiles have been calculated for two fragmentations of (CCl₄)⁺, into [(CCl₂)⁺ + Cl₂], and into [(CCl₃)⁺ + Cl^?], in the latter of which the reaction proceeds via a rather stable intermediate; for the fragmentation of three electronic states of (CCl₃)⁺ into [(CCl₂)⁺ + Cl^?], where the ground singlet state and first triplet state of (CCl₃⁺ yield the ground doublet state of (CCl₂)⁺, but the first excited singlet of (CCl₃)⁺ yields the first excited doublet of (CCl₂)⁺ ; and for the fragmentation of the ground state of (CCl₃)⁺ into [(CCl)⁺ + Cl₂].     

FTIR study of the Cl- and Br-atom initiated oxidation of trichloroethylene

The Cl- and Br- initiated oxidations of CHCl(DOUBLEBOND)CCl₂ in 700 torr of air at 296 K have been studied using a Fourier transform infrared spectrometer. Rate constants k(Cl+CHCl(DOUBLEBOND)CCl₂)=(7.2±0.8)×10⁻¹¹ and k(Br+CHCl(DOUBLEBOND)CCl₂)=(1.1±0.4)×10⁻¹³ cm³ molecule⁻¹ s⁻¹ were determined using a relative rate technique with ethane and ethylene as references, respectively. The major products observed were CHXClC(O)Cl, (X=Cl or Br), CHClO, and CCl₂O. Combining results obtained for the Cl-initiated oxidation of CHCl₂(SINGLEBOND)CHCl₂, we deduced that Cl-addition on trichloroethylene occurs via channel 1a, Cl+CHCl(DOUBLEBOND)CCl₂→ CHCl₂(SINGLEBOND)CCl₂, (100±12)%. Self-reaction of the subsequently generated peroxy radicals CHCl₂(SINGLEBOND)CCl₂O₂ leads to CHCl₂CCl₂O radicals which were found to decompose via channel 8a, CHCl₂C(O)Cl+Cl, (91±11)% of the time, and channel 8b, CHCl₂+CCl₂O, (9±2)%. The reaction Br+CHCl(DOUBLEBOND)CCl₂→CHBrCl(SINGLEBOND)CCl₂ (17a) accounted for ≥(96±11)% of the total reaction. Decomposition of the CHBrCl(SINGLEBOND)CCl₂O radicals proceeds (≥93±11)% via CHBrClC(O)Cl+Cl. As part of this work, k(Cl+CHCl₂C(O)Cl)=(3.6±0.6)×10⁻¹⁴ and k(Cl+CHCl₂(SINGLEBOND)CHCl₂)=(1.9±0.2)×10⁻¹³ cm³ molecule⁻¹ s⁻¹ were measured. Errors reported above include statistical uncertainties (2σ) and estimated systematic uncertainties. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet: 29: 695–704, 1997.     

The mass spectra of 1,1,1-trichloro-2,4-pentanedione and its Al(III), Cr(III), Fe(III), Mn(II), Co(II) and Cu(II) complexes

The compounds 1,1,1-trichloro-2,4-pentanedione, Cu(II)tca₂, Co(II)tca₂, Mn(II)tca₂, Al(III)tca₃, Cr(III)tca₃ and Fe(III)tca₃ (tca?1,1,1-trichloro-2,4-pentanedionato, [CCl₃COCHCOCH₃]^?) have been prepared and their mass spectra have been obtained. The mass spectral results have been compared with findings for comparable fluorinated and nonhalogenated compounds. Comparisons are made in terms of internal redox reactions and hard and soft acid base theory. Rearrangement of chloride from ligand to metal accompanied by the elimination of CO or other neutral even electron fragments emerges as an important reaction for the ions of these compounds. While the internal redox reactions characteristic of all previous β-diketonate complex mass spectra still occur, their importance appears reduced to some degree by the facility of the chlorine rearrangement.     

Kinetics of γ-alumina chlorination by carbon tetrachloride

The kinetics of the reaction between γ-Al₂O₃ and gaseous CCl₄ has been studied by isothermal TG measurements in the temperature range 700—1123 K. The reaction starts with a weight gain which can be attributed to the chemisorption of the reactive gas. The weight loss vs. time curves at relatively high temperatures can be described by the contracting cylinder equation and at relatively low temperatures by first-order kinetics. The dependence of the initial reaction rate on the CCl₄ partial pressure follows the Langmuir—Hinshelwood rate expression. At 700—723 K, chemical control is thought to be predominant and an apparent activation energy of 212 kJ mole^?1 is found for the chlorination process.     

Pyrolysis of 1,1‐dichloro‐1‐fluoroethane in the absence and presence of added propene or CCl4: A computer‐aided kinetic study

The thermal dehydrochlorination CCl₂FCH₃ → CClFCH₂ + HCl has been studied in a static system between 610 and 700 K at pressures ranging from 14 to 120 torr. The experiments were performed in the absence and presence of an added inhibitor (0.5 to 7 torr of C₃H₆) or catalyst (2 to 8 torr of CCl₄). The evolution of the reaction was followed by measuring the pressure rise in the quartz reaction vessel and analyzing the products by gas chromatography. All the experimental results can be explained quantitatively in terms of a reaction model both radical and molecular. The molecular dehydrochlorination has an activation energy of 57.05 kcal/mol and a preexponential factor of 10^14.02 s⁻¹. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 191–197, 2001     

Plasma-chemical reactions in weakly decomposed CCl4

For the case of weak feed gas decomposition, where the concentration of CCl₄ exceeds those of decomposition and built-up products, the emission of CCl* is shown to originate from dissociative excitation of CCl₄. With electron concentration measured independently, the kinetics of CCl₄ decomposition has been extracted from the time dependence of the CCl* intensity. Supported by EPR determinations of radical concentrations in rapidly flowing CCl₄ and CCl₄/O₂ afterglows, the primary decomposition reaction is shown to be the electron impact dissociation into CCl₃ and Cl. Its rate constant (k ₁=4×10^–8 cm³s^–1) indicates strongly that dissociative electron attachment is the main reaction channel at least at r.f. power densities just above the threshold of a self-maintaining discharge. At extremely low mean electron energies the emission of a continuum is observed, which is tentatively ascribed to the radiative CCl₃-Cl recombination.     

On the mechanism of the Kharash reaction catalyzed by Fe(CO)5

Fe(CO)₅ is sufficiently stable at 80 °C in benzene solution and its thermal decomposition is not accelerated in the presence of phenyl cinnamate or/and DMF. The decomposition is accelerated by CCl₃Br (drastically) and by CCl₄ (to a lesser extent). DMF accelerates the reaction of Fe(CO)₅ with CCl₄. The (FeCl(DMF)₅]²⁺[Cl₃FeOFeCl₃]^2– complex has been isolated as a product; its composition and structure have been determined by X-ray analysis. The obtained data indicate the absence of coordination of DMF or/and an olefin with Fe⁰ species at the stage preceding oxidation. The mechanisms of the generation of CCl₃ radicals in thermal and photochemical Kharash reactions in the presence of Fe(CO)₅ are basically different. The probable pathways of the effect of DMF on the rate of the oxidative decomposition of Fe(CO)₅ are discussed.For Part 2, see Ref. 1.Translated from IzvestiyaAkademii Nauk. Seriya Khimicheskaya, No. 4, pp. 916–919, April, 1996.     

Chemically induced dynamic nuclear polarization and the mechanism of the reaction of Et<Subscript>3</Subscript>Al with CCl<Subscript>4</Subscript> in the presence of transition metal complexes

Integral effects of chemically induced ¹H and ¹³C nuclear polarization are reported for the reaction of Et₃Al with CCl₄ catalyzed by Pd(acac)₂, Cu(acac)₂, and Cp₂TiCl₂; for the reaction of (n-C₈H₁₇)₃Al with CCl₄ in the absence of a catalyst and in the presence of Ni(acac)₂; and for the reaction of the cyclic organoaluminum compound 1-ethyl-3-butylaluminacyclopentane with CCl₄ in the presence of Pd(acac)₂. A scheme of the catalytic cycle of this reaction predicting the formation of both radical and nonradical products is derived from the observed chemically induced dynamic nuclear polarization (CIDNP) effects and from data on the products of the reaction between Et₃Al and CCl₄ in the presence of Pd(acac)₂. According to the results of qualitative analysis of the CIDNP effects, the reactions of the trialkylalanes and the cyclic organoaluminum compound with CCl₄ in the presence of various metal complexes proceeded via similar mechanisms.     

The rate coefficients for the thermal decomposition of CCl3O2NO2

The thermal decomposition of CCl₃O₂NO₂ has been reevaluated based on new rate data for the reaction of Cl + NO₂. The revised rate coefficient for CCl₃O₂NO₂ thermal decay at about 1 atm total pressure (mainly N₂) is 1.42 × 10¹⁶ × exp(?11500/T) s^?1 from 268–298 K.     

Kinetics and mechanism for the thermal chlorination of chloroform in the gas phase: Inclusion of HCl elimination from CHCl3

HCl elimination from chloroform is shown to be the lowest energy channel for initiation in the thermal conversion of chloroform to CCl₄, with chlorine gas in the temperature range of 573–635 K. Literature data on this reaction is surveyed and we further estimate its kinetic parameters using ab initio and density functional calculations at the G3//B3LYP/6‐311G(d,p) level. Rate constants are estimated and reported as functions of pressure and temperature using quantum RRK theory for k( E ) and master equation analysis for fall‐off. The high‐pressure limit rate constant of this channel is k(CHCl₃ → ¹CCl₂ + HCl) = 5.84 × 10⁴⁰ × T ^?8.7 exp(?63.9 kcal/mol/ RT ) s^?1, which is in good agreement with literature values. The reactions of ¹CCl₂ with itself, with CCl₃, and with CHCl₃ are incorporated in a detailed mechanistic analysis for the CHCl₃ + Cl₂ reaction system. Inclusion of these reactions does not significantly change the mechanism predictions of Cl₂ concentration profiles in previous studies (Huybrechts, Hubin, and Van Mele, Int J Chem Kinet 2000, 32, 466) over the temperature range of 573–635 K; but Cl₂, CHCl₃, C₂Cl₆ species profiles are significantly different at elevated temperatures. Inclusion of the ¹CCl₂ + Cl₂ → CCl₃ + Cl reaction (abstraction and chain branching), which is found to have dramatic effects on the ability of the model to match to the experimental data, is discussed. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 647–660, 2003