Product Channels of the N2 (A3Σ+u) + O2 interaction

Products of the N₂(A) + O₂ reaction were measured in a discharge-flow reactor. N₂O accounts for only (2 ± 0.5)% of the reaction, contrary to recent reports, and O-atoms for 165 ± 10)% if N₂(A) is quantitatively produced from Ar3 with excess N₂ This assumption is examined and specific N₂(A) + O₂ rate parameters are estimated.     

Barrier height for the abstraction reaction of methylene with hydrogen,CH2(3B1) + H2 → CH3 + H

The abstraction reaction of methylene with hydrogen reinvestigated with a double zeta plus polarization basis at the configuration interaction level. The results are found to be very similar to those previously obtained without polarization functions, in line with previous findings at the SCF level. The barrier is computed to be 11.8 kcal/mole when an estimate of the effect of quadruple excitations is included.     

On the mechanism of the ion-molecule reaction CH3+ + CH4 = C2H5+ + H2

Experimental evidence supporting the “direct” reaction model and the “intermediate complex” model for the reaction CH₃⁺(CH₄, H₂)C₂H₅⁺ are analysed. It is shown that the evidence for the former can equally well be interpreted in terms of a proposed model of persistent complex formation and decay. The plausibility of a “direct” mechanism is discussed and is found to be poor.     

The rate constant for the reaction O3 + NO2 → O2 + NO3 over the temperature range 259–362 °K

The rate constant for the reaction of ozone with nitrogen dioxide has been measured over the temperature range 259 to 362°K, using a stopped-flow system coupled to a beam sampling mass spectrometer. A fit of the data to the Arrhenius equation gave: k = (9.44 ± 2.46) × 10¹⁰ exp[(?2509 ± 76)/T] cm³ mol^?1 sec^?1.     

Theoretical study of the reaction H + ClCH3 → HCl + CH3

The reaction H + ClCH₃ has theoretically studied in a LEPS potential energy surface with a single-particle approximation for the methyl group. The LEPS adjustable parameters were selected to reach a good agreement with experimental values of activation energy and exothermicity. A wide set of quasi-classical trajectories for that system has been calculated within a energy range covering the significative values of relative velocities at temperatures between 300 and 1000 K. Calculated reactive cross sections increase with translational energy and with the initial vibrational level, but they are not influenced by rotational excitation of the reactants. Microscopic and total reaction rate constants have been obtained within the temperature range and agree quite well with available experimental results. Final energy distribution shows that most of the exoergicity is consumed in increasing the relative velocity of the products, while HCl molecules remain in their vibrational ground state.     

Studies on the reaction N + N3 → N2(B 3Πg) + N2(X 1Σ+g)

Strongly enhanced N₂ first positive emission N₂(B ³Π_g → A ³Σ⁺_u) has been observed on addition of N atoms into a flowing mixture of Cl and HN₃. The dependence of the emission intensity on N atom concentration gave a rate constant for the reaction N + N₃ → N₂(B ³Π_g) + N₂(X ¹Σ⁺_g) of _i(1.6 ± 1.1) × 10^?11 cm³ molecule^?1 s^?1. That for the reaction Cl + HN₃ → HCl + N₃ is (8.9 ± 1.0) × 10^?13 cm³ molecule^?1 s^?1 from the decay of the emission. Comparison of the emission intensity in ClHN₃ with that in ClHN₃N gave the rate constant of the reaction N₃ + N₃ → N₂(B ³Π_g) + 2N₂(X ¹Σ⁺_g) as 1.4 × 10^?12 cm³ molecule^?1 s^?1 on the assumption that N + N₃ yields only N₂(B ³Π_g) + N₂(X ¹Σ⁺_g).     

Photodissociation of the dimer ions Ar+2, Ne+2, and (CO2)+2

The tandem quadrupole photodissociation mass spectrometer has been used to study photodissociation reactions of Ar⁺₂, Ne⁺₂, and (CO₂)⁺₂. The cross sections for photodissociation of Ar⁺₂ exhibited a strong dependence on ion source pressure, varying from 2 × 10 ^?18cm² at 0.1 torr to 6 × 10^?19cm² at 0.5 torr. A large photodissociation cross section (2 × 10^?17cm² for the reaction (CO₂)⁺₂ → CO⁺₂+ CO₂ was observed at the red end of the visible spectrum (580–620 nm) suggesting that this may be an important reaction in CO₂ rich planetary ionspheres such as that of Mars.     

Ab initio study of the two competitive channels HO2 + H → H2 + O2 and HO2 + H → H2O + O

Saddle point geometries and barrier heights have been calculated for the H abstraction reaction HO₂(²A″)+H(²S) → H₂(¹Σ⁺_g)+O₂(³Σ⁻_g) and the concerted H approach-O removing reaction HO₂ (²A″)+H(²S) → H₂O(¹A₁)+O(³P) by using SDCI wavefunctions with a valence double-zeta plus polarization basis set. The saddle points are found to be of C_s symmetry and the barrier heights are respectively 5.3 and 19.8 kcal by including size consistent correction. Moreoever kinetic parameters have been evaluated within the framework of the TST theory. So activation energies and the rate constants are estimated to be respectively 2.3 kcal and 0.4×10⁹ ℓ mol⁻¹ s⁻¹ for the first reaction, 20.0 kcal and 5.4.10⁻⁵ ℓ mol⁻¹ s⁻¹ for the second. Comparison of these results with experimental determinations shows that hydrogen abstraction on HO₂ is an efficient mechanism for the formation of H₂ + O₂, while the concerted mechanism envisaged for the formation of H₂O + O is highly unlikely.     

One-step synthesis of pentavalent triphenylantimony derivatives Ph3Sb(OSiR3)2, Ph3Sb(OCH2CH2)2NH and Ph3Sb(OCH2CH2NMe2)2: X-ray molecular structure of Ph3Sb(OSiMe3)2

Pentavalent bis(triorganosiloxy)triphenylantimony derivatives, Ph₃Sb(OSiR₃)₂ (R = Me, Ph), were synthesized by reaction of triphenylantimony with trimethyl- or triphenylsilanol in the presence of tert-butylhydroperoxide by the mild reaction conditions (0-5 °C, 2 h). The reaction of triphenylantimony with diethanolamine in the presence of tert-butylhydroperoxide gave the cyclic compound Ph₃Sb(OCH₂CH₂)₂NH. The mixture of Ph₃SbO and Ph₃Sb(OCH₂CH₂NMe₂)₂ was obtained by the reaction of triphenylantimony with 2-(N,N-dimethylamino)ethanol in the presence of tert-butylhydroperoxide.     

Mobilities of H+3 and HeH+ ions in helium gas and rate coefficient for HeH+ + H2 → H+3 + He

The mobilities of mass-identified H⁺₃ and HeH⁺ ions in helium and the reaction rate coefficient for HeH⁺ + H₂ → H⁺₃ + He have been measured by a drift-tube quadrupole mass spectrometer at 300 K. The zero-field reduced mobilities of H⁺₃ and HeH⁺ ions, corrected to 273 K, are 31.0 ± 0.8 and 23.4 ± 0.6 cm² V^?1 s^?1 respectively. The reaction rate coefficient was found to be (1.26 + 0.16) × 10^?9 cm³s^?1 and was observed to be independent of the mean ion kinetic energy in the range from 0.04 to 0.3 eV.     

Kinetics of the reaction OH (v = 0) + O3 → HO2 + O2

The rate constant of the reaction OH (v = 0) + O₃

HO₂ + O₂ was measured over the temperature range from 220 to 450°K at total pressures between 2 and 5 torr using ultraviolet fluorescent scattering for the detection of OH radicals. An Arrhenius expression, k₁ = 1.3 × 10^?12 exp(?1900/RT) cm³/sec was obtained and the rate constant for the reaction HO₂ + O₃

OH + 2O₂ was inferred to be less than 0.1 k₁ over the entire temperature interval.     

Determination of the rate constant for the reaction NH3 + OH → NH2 + H2O

The rate constant for the reaction NH₃ + OH → NH₂ + H₂O was determined by the comparison of the calculated induction period data with experiments by the shock tube technique in the range 1360–1840 K, for NH₃-H₂-O₂-Ar mixtures. The rate constants can be represented by the expression k = 10^12.49±0.04exp[(?1.95±0.15) kcal/,RT] cm³ mol^?1 s^?1.     

CH2+O2反应的反应机理

The mechanisms of the CH2＋ O2→ H2O＋ CO and CH2＋ O2→ H2＋ CO2 reactions have been studied by performing ab initio CAS(8,8)/6-31G(d,p) calculations, and five intermediates(IMn) and eight transitions(TSn) have been located along the reaction paths. The predicted path for the CH2＋ O2→ H2O＋ CO is: CH2＋ O2→ TS1→ IM1→ TS2→ IM2→ TS3→ IM3→ TS4→ IM4a→ TS5→ H2O＋ CO. For the CH2＋ O2→ H2＋ CO2 reaction, there are two paths: (i) CH2＋ O2→ TS1→ IM1→ TS2→ IM2→ TS3→ IM3→ TS6→ H2＋ CO2 and (ii) CH2＋ O2→ TS1→ IM1→ TS2→ IM2→ TS3→ IM3→ TS4→ IM4a→ TS7→ IM4b→ TS8→ H2＋ CO2, with the latter path more favorable energetically.     

CH3NO2和CH3自由基吸氢反应途径和变分速率常数计算

采用MP2(full)/6-311G(d, p)从头算方法,优化了硝基甲烷和甲基自由基吸氢反应的过渡态结构,经QCISD(T)方法进行能量校正,得出该反应的正逆向反应的活化位垒分别是58.21 kJ•mol－1和67.17 kJ•mol－1.沿IRC分析指出该反应是氢转移协同反应,而且在反应途径上存在一个引导反应进行的振动模式,这一反应模式引导反应进行的区间在反应坐标S的-0.9～1.0(amu)1/2bohr之间;在温度为800～2600 K范围内,运用改进的变分过渡态理论(ICVT),计算了该反应的速率常数,并与实验类比所得的速率常数随温度的变化趋势进行了比较.     

2D and 3D quantum scattering calculations on the CH4 + OH → CH3 + H2O reaction

The effect on the thermal rate constant and the differential cross-sections of varying the dimensionality of quantum scattering calculations of a polyatomic reaction is investigated. The rotating bond approximation (RBA; 3D) and a rotating line approximation (RLA; 2D) are used for the CH₄ + OH → CH₃ + H₂O reaction. It is found that the RBA and RLA results are in close agreement when an adiabatic treatment is used for the degree of freedom which is treated explicitly in the RBA but not in the RLA.     

Vapour-liquid equilibrium data for the systems C2H6 + N2, C2H4 + N2, C3H8 + N2, and C3H6 + N2

High pressure vapour-liquid equilibrium data for the C₂H₆ + N₂, C₂H₄ + N₂, C₃H₈ + N₂, and C₃H₆ + N₂ systems are presented. The data are obtained isothermally in the range from 200 K to 290 K. For each point of data, temperature, pressure and liquid and vapour phase mole fractions are measured.Values for the vapour phase mole fractions are calculated from the obtained pressure, temperature and liquid phase mole fractions. The calculated values are compared with the experimental results, and it is found that the average mean deviation between calculated and experimental mole fractions is less than 0.009 for the systems considered in this work.     

A rate constant for CH2(3B1) + CH3

Triplet methylene, CH₂(³B₁), and methyl radicals were produced by flash photolysis of a mixture of ketene and azomethane. A computer fit of the product ratios, using the known rate constants for CH₂ + CH₂, and CH₃ + CH₃, requires a rate constant of 5.0 × 10^?11 cm³ molecule^?1s^?1 for the reaction CH₂ + CH₃ ? C₂H₄ + H.     

Rate of the reaction I2 + F2 → products

The rate coefficient, k1, for the reaction I2+F2k1→ products has been measured at room temperature to be k1 = (1.9 = 0.4) × 10?15 cm3/molecule s. The macroscopic rate is compared to microscopic cross-section data obtained from molecular beam experiments and is found to be consistent with the bimolecular reaction I2 + F2→ I2F + F.DG|National Research Council/Resident Research Associate.     

Theoretical sstudy on the Co2+OH2+/Co3+OH2+ electron transfer reactivity

This paper presents a contact distance dependence analysis scheme and an abinitio calculation application for the electron transfer (ET) reactivity of Co²⁺OH₂/Co³⁺OH² reacting pair. The applicability of these schemes and the corresponding models has been discussed. The contact distance (R _CoCo) dependence of the relevant quantities has been analyzed. The results indicate that the activation energy from the accurate PES method agrees well with that from the anharmonic potential method, and they are obviously better than that from the harmonic potential method. The pair distribution function varies from 10⁻² to 10⁻⁵ along withR _CoCo changing from 1.20 to 0.35 nm. The coupling matrix element exponentially decays along with the increase ofR _CoCo, and the effective electronic coupling requiresR _CoCo smaller than 0.75 nm. In the range from 0.50 to 0.75 nm forR _CoCo, the corresponding electronic transmission coefficient falls within 1.0—10⁻⁶. The local ET rate also exponentially decays along with the increase ofR _CoCo due to the electronic factor. Since the contribution from the pair distribution function to the total ET rate is an inverse measure of that from the electronic factor, the variation of the spherically averaged local ET rate along withR _CoCo exhibits a parabola with a maximum at 0.50 nm ofR _CoCo. This maximum is close to the overall observed ET rate value. For this mono-hydrated transition metal ionic system, the ET rate generally is about 10⁶ L·mol⁻¹·s⁻¹ in gaseous process. Further, since it is impossible to experimentally determine the structures and their PESs of these hydrated systems, especially for the unstable intermediate species,ab initio calculations can play an effective auxiliary role in discussing the ET reactivities of these kinds of reacting systems.     

CH4+O(3P)→CH3+OH反应的准经典轨线研究

用准经典轨线方法研究了O（3P）与CH4的反应，计算结果表明，CH4（υ＝0，j＝0）与O（3P）的反应在低及高的碰撞参数下都是直接反应，无短寿命的碰撞复合物生成，产物OH以向后散射为主，基本上处于振转基态.CH4（υ＝1，j＝1）与O（3P）的反应在低及高的碰撞参数下反应机理不一样。在低碰撞参数下是直接反应，无短寿命的碰撞复合物生成，产物OH以向后散射为主，主要处于振动基态，转动基本上是冷的，但比高碰撞参数下的热.在高的碰撞参数下则生成短寿命的碰撞复合物，产物OH以向前散射为主，表现出明显的周边动力学反应的特征，主要处于振动激发态（υ＝1），但转动仍然是较冷的。