14700-96-0Relevant academic research and scientific papers
Collision energy dependence of the O(1D) + HCl -OH + Cl( 2P) reaction studied by crossed beam scattering and quasiclassical trajectory calculations on ab initio potential energy surfaces
Kohguchi, Hiroshi,Suzuki, Toshinori,Nanbu, Shinkoh,Ishida, Toshimasa,Mil'nikov, Gennady V.,Oloyede, Ponmile,Nakamura, Hiroki
, p. 818 - 825 (2008)
The dynamics of the O(1D) + HCl → OH + Cl(2P) reaction are investigated by a crossed molecular beam ion-imaging method and quasiclassical trajectory calculations on the three ab initio potential energy surfaces, the ground 11A′ and two excited (1 1A″ and 21A′) states. The scattering experiment was carried out at collision energies of 4.2, 4.5, and 6.4 kcal/mol. The observed doubly differential cross sections (DCSs) for the Cl(2P) product exhibit almost no collision energy dependence over this inspected energy range. The nearly forward-backward symmetric DCS indicates that the reaction proceeds predominantly on the ground-state potential energy surface at these energies. Variation of the forward-backward asymmetry with collision energy is interpreted using an osculating complex model. Although the potential energy surfaces obtained by CASSCF-MRCI ab initio calculations exhibit relatively low potential barriers of 1.6 and 6.5 kcal/mol for 1 1A″ and 21A′, respectively, the dynamics calculations indicate that contributions of these excited states are small at the collision energies lower than 15.0 kcal/mol. Theoretical DCSs calculated for the ground-state reaction pathway agree well with the observed ones. These experimental and theoretical results suggest that the titled reaction at collision energies less than 6.5 kcal/mol is predominantly via the ground electronic state.
Photodissociation dynamics of phosgene: New observations by applying a three-dimensional imaging technique
Einfeld, Tina,Chichinin, Alexei,Maul, Christof,Gericke, Karl-Heinz
, p. 2803 - 2810 (2002)
The three-dimensional (3D) momentum vector of single Cl atoms in the uv photodissociation of phosgene was directly observed using the recently developed 3D imaging technique. The previous results as there is the generation of chlorine in the 2P/3/2 electronic ground state as well as in the electronically excited 2P1/2 state, the highly spin selective process with bimodal kinetic energy distribution and the overall decay mechanism as well as the branching ratios were confirmed. The anisotropy parameter β and its speed dependence were observed for the first time.
Nonradiative decay pathways of electronic states of group IV tetrafluoro and tetrachloro molecular ions studied with synchrotron radiation
Creasey, J. C.,Lambert, I. R.,Tuckett, R. P.,Codling, K,Frasinski, L. J.,at al.
, p. 3295 - 3306 (1990)
The nonradiative decay channels of the valence electronic states of the gas-phase tetrahedral ions CF4+, SiF4+, CCl4+, SiCl4+, and GeCl4+ have been studied in the range 35-100 nm by a novel form of photoionization mass spectrometry.Tunable vacuum UV radiation from a synchrotron source ionizes the parent neutral molecule, and electrons and ions are detected by the photoelectron-photoion coincidence technique.The experiment is repeated continuously as a function of photon energy, and a three-dimensional histogram of photon energy versus ion time of flight versus coincidence count rate is produced.By taking cuts through this histogram, photoionization curves for the different fragment ions can be extracted.The appearance energies of the fragment ions (e.g., CF2+ from CF4, CCl+ from CCl4) occur at the adiabatic ionization potential of an electronic state of the parent ion, and not at the thermodynamic appearance energy of that ion.Attempts to measure the kinetic-energy releases in the fragmentation pathways have only been partially successful.The results are complementary to those of recent experiments to probe the radiative decay of these electronic states of MX4+ , where the T2 and A1 third and fourth excited electronic states can show radiative decay to a surprising degree.The decay dynamics of the and states of MX4+ are reviewed.In general, the fluorides show different behavior to the analogous chlorides, and the carbon species behaves differently to the corresponding silicon or germanium species.
Primary and secondary dissociation pathways in the ultraviolet photolysis of Cl2O
Nelson, Christine M.,Moore, Teresa A.,Okumura, Mitchio,Minton, Timothy K.
, p. 8055 - 8064 (1994)
The photodissociation of dichlorine monoxide (Cl2O) at 308, 248, and 193 nm was studied by photofragment translational energy spectroscopy.The primary channel upon excitation at 308 and 248 nm was Cl-O bond fission with production of ClO + Cl.A fraction of the ClO photoproducts also underwent spontaneous secondary dissociation at 248 nm.The center-of-mass translational energy distribution for the ClO + Cl channel at 248 nm appeared to be bimodal with a high energy component that was similar in shape to the 308 nm distribution and a second, low energy component with a maximum close to the threshold for the 2Cl + O(3P) channel.Observation of a bimodal distribution suggests that two pathways with different dissociation dynamics lead to ClO + Cl products.The high product internal energy of the second component raises the possibility that ClO is formed in a previously unobserved spin-excited state a 4Σ-.Following excitation at 193 nm, a concerted dissociation pathway leading to Cl2 + O was observed in addition to primary Cl-O bond breakage.In both processes, most of the diatomic photofragments were formed with sufficient internal energy that they spontaneously dissociated.The time-of-flight distributions of the Cl2 + O products suggest that these fragments are formed in two different channels Cl2(3Π) + O(3P) and Cl2(X 1Σ) + O(1D).
Thermochemistry is not a lower bound to the activation energy of endothermic reactions: A kinetic study of the gas-phase reaction of atomi-chlorine with ammonia
Gao, Yide,Alecu,Hsieh,Morgan, Brad P.,Marshall, Paul,Krasnoperov, Lev N.
, p. 6844 - 6850 (2006)
The rate constant for Cl + NH3 → HCl + NH2 has been measured over 290-570 K by the time-resolved resonance fluorescence technique. Ground-state Cl atoms were generated by 193 nm excimer laser photolysis of CCl4 and reacted under pseudo-first-order conditions with excess NH3. The forward rate constant was fit by the expression k1 = (1.08 ± 0.05) × 10-11 exp(-11.47 ± 0.16 kJ mol-1/RT) cm3 molecule-1 s-1, where the uncertainties in the Arrhenius parameters are ±1 σ and the 95% confidence limits for k1 are ±11%. To rationalize the activation energy, which is 7.4 kJ mol -1 below the endothermicity in the middle of the 1/T range, the potential energy surface was characterized with MPWB1K/6-31++G(2df,2p) theory. The products NH2 + HC1 form a hydrogen-bonded adduct, separated from Cl + NH3 by a transition state lower in energy than the products. The rate constant for the reverse process k-1 was derived via modified transition state theory, and the computed k-1 exhibits a negative activation energy, which in combination with the experimental equilibrium constant yields k1 in fair accord with experiment.
Measuring gas-phase chlorine atom concentrations: Rate constants for Cl + HN3, CF3I, and C2F5I
Manke II,Setser
, p. 153 - 159 (1998)
A convenient method is reported for the measurement of gas-phase Cl atom concentrations in the 1011-1013 atoms cm-3 range in a flow reactor. The titration reaction with vinyl bromide is used to measure the absolute Cl atom concentration, and the relative Cl atom concentration is monitored by the HCl(ν) infrared emission intensity produced by the reaction of Cl atoms with hydrogen sulfide. A microwave discharge through dilute flows of Cl2, CCl4, CFCl3, and CF2Cl2 in Ar were characterized as sources of Cl atoms in the flow reactor. The elementary rate constants for reaction of Cl atoms with HN3, CF3I, and C2F5I were measured as (1.1 ± 0.3) × 10-12, (5.1 ± 1.5) × 10-13, and (3.9 ± 0.8) × 10-12 cm3 molecule-1 s-1, respectively, at 300 K. These rate constants were obtained after adjustment of the apparent rate constants for secondary reactions.
Surface aligned photochemistry: photodissociation of Cl2 and Cl2...Cl adsorbed on LiF (001)
Giorgi, Javier B.,Naumkin, Fedor Y.,Polanyi, John C.,Raspopov, Sergei A.,Sze, Newman S. -K
, p. 9569 - 9581 (2000)
In this study, an attempt was made to photolyze chlorine from submonolayer to multilayer coverage on a nonreactive dielectric substrate, LiF(001). Low laser energies and chlorine coverages were used in order to observe photochemical processes. An additional channel referred to as channel A for Cl atoms was found for photodissociation of chlorine adsorbed on LiF(001) surface by 351 nm laser radiation.
A laser flash photolysis-resonance fluorescence kinetics study of the reaction Cl(2P) + CH4 -> CH3 + HCl
Ravishankara, A. R.,Wine, P. H.
, p. 25 - 30 (1980)
The technique of laser flash photolysis-resonance fluorescence is employed to study the kinetics of the reaction Cl(2P) + CH4 -> CH3 + HCl over the temperature range 221-375 K.Chlorine atoms are produced by photolysis of Cl2 at 355 nm.At temperatures =1L) and high (klH) methane concentrations.For Cl2/CH4/CCl4/He and Cl2/CH4/Ar reaction mixtures, the bimolecular rate constant (k1) is independet of methane concentration with k1 ca. k1L. k1 and k1L are in good agreement with previous results obtained using the flash photolysis-resonance fluorescence technique while k1H is in good agreement with previous results obtained using the didcharge flow-resonance fluorescence and competitive chlorination techniques.At 298 K the measured bimolecular rate constant is independet of the identity of the chemically inert gases in the reaction mixture and in good agreement with all previous investigations.The low temperature results obtained in this investigation and all previous investigations can be rationalized in terms of a model which assumes that the Cl(2P1/2) state reacts with CH4 much faster than the Cl(2P3/2) state.Extrapolation of this model to higher temperatures, however, is not straightforward.
Mechanism and Rate Constants for the Reactions of Cl Atoms with HOCl, CH3OCl and tert-C4H9OCl
Kukui,Roggenbuck,Schindler
, p. 281 - 286 (1997)
Reactions of Cl atoms with HOCl (1), CH3OCl (2) and C4H9OCl (3) have been investigated at 300 K using discharge flow LIF/MS technique. The mechanism and reaction rate constants were determined by monitoring absolute rates of hypochlorite and Cl atom consumption together with the build-up of reaction products. Based on the yields of Cl2 and OH in (1a), Cl2 and CH3O in (2a) and Cl2 in (3a), as measured by MS/LIF, the reactions of Cl atom with the hypochlorites investigated in this work were found to proceed predominantly via the Cl atom abstraction channel with k1a/k1 = (0.96±0.05), k2a/k2 = (0.85±0.06), k3a/k3 = (1.01 ±0.05). HOCl + Cl → Cl2 + OH (1a) CH3OCl+Cl → Cl2 + CH3O (2a) C4H9OCl + Cl→ Cl2 +other products (3a) The reaction rate constants were determined to be k1, = (2.28±0.09)·10-12, k2 = (6.0±0.2)·10-11, and k3 = (4.26±0.2)·10-11, all in units cm3-molecule-1·s-1. A reevaluation of the heat of formation of HOCl yielded ΔHf0 (298 K) = -75.1 kJ·mol-1. VCH Verlagsgesellschaft mbH 1997.
The rate and equilibrium constants for the reaction NO3? + Cl- ? NO3- + Cl? in aqueous solutions
Poskrebyshev,Huie,Neta
, p. 1964 - 1970 (2003)
The rate and equilibrium constants for the reaction NO3? + Cl- ? NO3- + Cl? in aqueous solutions were measured by pulse radiolysis. The formation and decay of the nitrate radical, NO3?, and the dichloride radical anion, Cl2?-, in irradiated aqueous solutions containing nitric acid and chloride ions were followed under various conditions. Because of the complexity of the system, the forward rate constant and the equilibrium constant were derived from modeling the experimental results, including secondary formation and decay reactions. The modeling study results in an equilibrium constant of Keq = (3.5 ± 0.5) at an ionic strength between 0.1 and 1 mol L-1 and a forward rate constant k1 = (3.5 ± 0.5) × 108 L mol-1 s-1. In contrast with previous reports, no effect of ionic strength (up to 2 mol L-1) on the forward rate constant was observed.
