Theoretical investigation on the reaction of N2O and CO catalyzed by Fe(C6H6)

The reaction of N₂O with CO, catalyzed by Fe⁺(C₆H₆) and producing N₂ and CO₂, has been investigated at the UB3LYP/6-311+G(d) level. The computation results revealed that the reaction of Fe⁺(C₆H₆), N₂O and CO, is an O-atom abstraction mechanism. For the reaction channels, the geometries and the vibrational frequencies of all species have been calculated and the frequency modes analysis also have been given to elucidate the reaction mechanism. On the basis for geometry optimizations, the thermodynamic data of these reactions channels have been calculated using the statistical theory at 295.15 K and pressure of 0.35 Torr. Using Eyring transition state theory with Wigner correction, the activation thermodynamic data, rate constant and frequency factors for the these reaction channels also have been given. The results showed that CO and N₂O do not react without catalyst and Fe⁺(C₆H₆) can excellently mediate the reaction of N₂O and CO.     

High-pressure Raman study of vibrational relaxation in N2O

The vibrational widths of the ν₁ and ν₃ Raman bands of N₂O were determined at pressures ranging from 8 bar to 2 kbar and temperatures varied from 25 to 150°C. The different dephasing theories including motional narrowing collisional models and resonant vibrational energy transfer theory were tested. A comparison of the theoretical predictions with the experimental data indicates the resonance VV transfer represents the dominant broadening mechanism. The observed frequency shifts between isotropic and anisotropic components of the bands were interpreted in terms of dipole-dipole interactions in dense N₂O.     

HCN + OH→CN + H2O反应理论研究

The reaction path of the reaction HCN + OH→ CN + H2O was traced with Fukui's theory of intrinsic reaction coordinate by using ab initio MO method (at UMP4/6-31G** level) with gradient technique. On this basis, the dynamics properties along the reaction path was investigated by reaction path Hamiltonian theory. The rate constants of this reaction at different temperatures were calculated by conventional and variational transition state theory with tunneling correction. The theoretically calculated rate constants are in good agreement with experimental results, this shows that the title reaction is an one step, direct reaction.     

Vibrational relaxation of CO2(00°1) and N2O(00°1) by NO

The far-from-resonance transfers and the de-excitation processes in CO₂-NO and N₂O-NO systems have been studied by measuring fluorescence decay rate constants of CO₂ or N₂O excited to the (00°1) level by laser radiation. The diagrams giving the variations of these rate constants versus the molar fraction of CO₂ or N₂O have been set out. From these diagrams, the relative importance of the V-V transfer and V-T de-excitation rate constants is discussed. The transfer rate constants have been calculated from a semiclassical theory in which the interaction potential is a sum of four atom-atom Morse potentials. The disagreement observed between calculated and experimental values probably results from the attractive multipolar forces which the theory does not take into account.     

FeZSM-5/N2O催化氧化苯制苯酚

苯一步氧化制苯酚，是有机物氧化合成中富有挑战性的研究课题之一。该文着重论述了在FeZSM-5及其一系列沸石催化剂上，应用氧化亚氮作为氧化剂使苯直接氧化制苯酚的研究进展。这一系列催化剂体系的特殊之处在于通过氧化亚氮在沸石分子筛上的分解获得具有催化活性的a－氧。详细讨论了在沸石分子筛上形成特殊结构的铁氧化物作为催化活性中心这一观点。由于这种催化体系对苯直接氧化制苯酚的反应有着很高的选择性，因此，这种比较经济和安全的制备苯酚的方法引起了人们的广泛关注。     

Rate constants of the O(D) reactions with N2, O2, N2O, and H2O at 295 K

Using a technique of laser flash photolysis coupled with vacuum ultraviolet laser-induced fluorescence spectroscopy, the rate coefficients of O(¹D) reactions with N₂, O₂, N₂O, and H₂O at 295 ± 2 K have been determined to be , k_O2=(4.06±0.24)×10^-11, k_N2O=(1.35±0.08)×10^-10 and . The quoted uncertainties include estimated errors and are the 95% confidence level. The k_N2 and k_N2O values obtained are larger than the current NASA/JPL recommendations by 26% and 16%, respectively, although they are still within the error limits associated with the recommendations.     

光引发BrC2F4Br+C2F4调聚反应的光强影响

实验发现，在光引发BrC2F4Br＋C2F4调聚反应中，光强（或光功率密度）能影响产品分布。提出了反应机理：此反应由加成反应与复合反应组成，而链转移反应可忽略．由此进行了动力学计算，为与实验结果吻合，拟合得的加成反应BrC2F4＋C2F4的速率常数为（2±1）×107cm3•mol-1•s-1，Br（C2F4）n≧2＋C2F4的速率常数为（1．2±0．4）×107Cm3•mol-1•s-1     

Observation by laser ionization spectroscopy of vibrationally excited nitric oxide following O(1D2) + N2O → 2NO

Nitric oxide in ν < has been detected using one-proton resonant laser ionization spectroscopy following the reaction of electronically excited oxygen atoms with nitrous oxide. The nascent rotational distribution appears to differ significantly from that observed at 300 K.     

Reaction path dynamics and theoretical rate constants for the SiH3Cl+H→SiH2Cl+H2 reaction by ab initio direct dynamics method

Ab initio direct dynamics method has been used to study the title reaction. Electronic structure information including geometries, gradients and force constants (Hessians) are calculated at the UQCISD/6-311+G^** level. Energies along the minimum energy path are improved by a series of single-point G2//QCISD calculations. The changes of the geometries, vibratioanal frequencies, potential energies and total curvature along the reaction path are discussed. The rate constants in the temperature range 200–3000 K are calculated by canonical variational transition state theory with small-curvature tunneling correction (CVT/SCT) method. The results show that the variational effect is small and in the lower temperature range, the small curvature tunneling effect is important for the reaction.     

A CASSCF/icMRCI study of the electric field gradient in low-lying electronic states of N2/N2

The electric field gradients (EFG’s) at the nucleus are calculated as a function of internuclear separation in the X²Σ_g⁺ and B²Σ_u⁺ electronic states of the nitrogen molecule cation using the internally contracted multireference configuration interaction (icMRCI) method. The EFG’s and potential energy functions (PEF’s) are used to estimate the ¹⁴N nuclear quadrupole coupling constants (NQCC’s) in the two electronic states as functions of vibrational and end-over-end rotational quantum numbers. The dependences of the computed constants on the basis set and reference configuration space are investigated. Since no counterpart for comparison of the calculated NQCC’s exists, the N₂⁺ results are supported by analogous calculations on the X¹Σ_g⁺ and A³Σ_u⁺ states of N₂, for which established data are available. The overall good quality of the icMRCI wave functions is further corroborated by a favorable agreement of spectroscopic constants derived from the corresponding PEF’s and experimental data. Variations of the EFG with internuclear separation are explained in terms of wave function composition, and used for gaining specific insight into the chemical bonding in N₂⁺ and N₂.     

Kinetics of O(1D) interactions with the atmospheric gases N2, N2O,H2O,H2, CO2, and O3

Rate coefficients for collisional removal of O(¹D) by six atmospheric gases have been measured by monitoring the appearance of O(³P) following photolytic production of O(¹D). The measured values, k_M±2σ, in units of 10^?11 cm^?3 molecule ^?1 s^?1 are k_O3 = 22.8±2.3, k_N2 = 2.52 ± 0.25, k_CO2 = 10.4 ± 1.0,k_H2O 195± 2.0, k_N2O = 11.7 ± 1.2, and k_H2, = 11.8±1.2.     

Mechanism of vibrational relaxation of CO2(υ1, υ2) by H2O

Vibrational relaxation of CO₂ by H₂O has been studied theoretically. Earlier theoretical works are critically analyzed. A new mechanism of V—R—T interaction is put forward and a functional equation for the probability factor is obtained. Collisions of CO₂ with H₂O adsorbed on a solid surface are also considered.     

Structural and spectroscopic properties of Hexamethylenetetramine cobalt(II) complex: [Co(NCS)2(hmt)2(H2O)2][Co(NCS)2(H2O)4] (H2O)

Synthesis, structure, spectroscopy and thermal properties of complex [Co(NCS)₂(hmt)₂(H₂O)₂][Co(NCS)₂(H₂O)₄] (H₂O) (I), assembled by hexamethylenetetramine and octahedral Co(II) metal ions, are reported. Crystal data for I: F_w 387.34, a=9.020(8), b=12.887(9), c=7.95(1) Å, =96.73(4), β=115.36(5), γ=94.16(4)°, V=820(1) Å³, Z=2, space group=P−1, T=173 K, λ(Mo-K)=0.71070 Å, ρ_calc=1.718567 g cm⁻³, μ=17.44 cm⁻¹, R=0.088, R_w=0.148. An interesting two-dimensional network is assembled via hydrogen bonds through coordinated and free water molecules. The d–d transition energy levels of Co(II) ion are determined by UV–vis spectroscopy and calculated by ligand field theory. The calculated results agree well with experiment ones.     

Direct dynamics studies on the hydrogen abstraction reactions CF3O+CH4(CD4)→CF3OH(CF3OD)+CH3(CD3)

The dynamics properties of the hydrogen abstraction reaction CF₃O+CH₄→CF₃OH+CH₃ are studied by dual-level direct dynamics method. Optimization calculations are preformed by B3LYP and MP2 with the 6-311G(d,p) basis set, and the single-point calculations are done at the multi-coefficient correction method based on quadratic configuration interaction with single and double excitations (MC-QCISD) method. The rate constants are evaluated by canonical variational transition-state theory with a small-curvature tunneling correction over a wide range of temperature 200–2000 K. The agreement between theoretical and experimental rate constants is good in the measured temperature range. The calculated results show that the variational effect is small and almost neglected over the whole temperature range, whereas, the tunneling correction plays a role in the lower temperature range. The kinetic isotope effect for the reaction is ‘normal’. The value of k_H/k_D is 2.38 at room temperature and it decreases with the temperature increasing.     

Conversion of NO in NO/N2, NO/O2/N2, NO/C2H4/N2 and NO/C2H4/O2/N2 Systems by Dielectric Barrier Discharge Plasmas

An experimental study on the conversion of NO in the NO/N₂, NO/O₂/N₂, NO/C₂H₄/N₂ and NO/C₂H₄/O₂/N₂ systems has been carried out using dielectric barrier discharge (DBD) plasmas at atmospheric pressure. In the NO/N₂ system, NO decomposition to N₂ and O₂ is the dominating reaction; NO conversion to NO₂ is less significant. O₂ produced from NO decomposition was detected by an on-line mass spectrometer. With the increase of NO initial concentration, the concentration of O₂ produced decreases at 298 K, but slightly increases at 523 K. In the NO/O₂/N₂ system, NO is mainly oxidized to NO₂, but NO conversion becomes very low at 523 K and over 1.6% of O₂. In the NO/C₂H₄/N₂ system, NO is reduced to N₂ with about the same NO conversion as that in the NO/N₂ system but without NO₂ formation. In the NO/C₂H₄/O₂/N₂ system, the oxidation of NO to NO₂ is dramatically promoted. At 523 K, with the increase of the energy density, NO conversion increases rapidly first, and then almost stabilizes at 93–91% of NO conversion with 61–55% of NO₂ selectivity in the energy density range of 317–550 J L⁻¹. It finally decreases gradually at high energy density. A negligible amount of N₂O is formed in the above four systems. Of the four systems studied, NO conversion and NO₂ selectivity of the NO/C₂H₄/O₂/N₂ system are the highest, and NO/O₂/C₂H₄/N₂ system has the lowest electrical energy consumption per NO molecule converted.     

CH2(X 3B1)自由基与N2O反应的研究

The reaction dynamics of methylene radical CH2(X3B1) with N2O was investigated by Time-Resolved Fourier Transform Infrared Spectroscopy(TR-FTIRS). Pure CH2(X3B1) radicalwas produced via laser photolysis of ketene at 351 nm. Nascent viabrationally excited products CO, NO and HCN were observed. Some reaction pathways which may lead to these products were proposed and a possible reaction mechanism was outlined.     

Magic cluster ion distributions: (NO)3+ (N2O)n and (NO)3+ (CO2)n

Supersonic jet expansions of mixtures of nitric oxide with either nitrous oxide or carbon dioxide have been investigated over a wide range of relative concentrations. Mixed molecular cluster ions of the form (NO) _m ⁺ (N₂O)_n and (NO) _m ⁺ (CO₂)_n are detected following non-resonant two-photon ionization. Over a wide range of intermediate concentrations, the cluster ion distributions (NO) ₃ ⁺ (N₂O)_n and (NO) ₃ ⁺ (CO₂)_n with n30 are significantly more intense than clusters containing other numbers of nitric oxide molecules. The extra abundance of these species is attributed to their especially stable structures and several possible forms are discussed. An intriguing possibility involves a stable cyclic nitric oxide trimer (or ion) when combined with nitrous oxide or carbon dioxide clusters.     

Calorimetric study of room temperature adsorption of N2O and CO on Cu(II)-exchanged ZSM5 zeolites

Copper ion-exchanged ZSM5 zeolites have been prepared with different cooper loadings from under- to over-exchanged levels. The adsorptions of N₂O and CO at 303 K have been studied using calorimetric method and infrared spectroscopy. The samples were additionally characterised by ammonia adsorption at 423 K. The active sites for both N₂O and CO are Cu(I) ions, which were formed as a result of pre-treatment in vacuum at 673 K.

Room temperature adsorption of nitrous oxide at low equilibrium pressures (up to 66.7 Pa) resulted in small amounts of chemisorbed N₂O (<0.2 molecule per one Cu ion). Differential heats of N₂O adsorption between 80 and 30 kJ/mol were obtained. Differential heats of CO adsorption between 140 and 40 kJ/mol were obtained. The obtained amounts of chemisorbed species in the investigated systems and the values of differential heats of both nitrous oxide and carbon monoxide demonstrate the dependence on the copper content.     

The change in the vibrational anharmonicity for FHRg, FArHRg, FArHN2 and FArHP2 (Rg=Ne, Ar, Kr)

The change in the vibrational anharmonic constant for the linear hydrogen-bonded complexes FHRg, FArHRg, FArHN₂, FArHP₂ (Rg=Ne, Ar, Kr) was determined at the MP2/6-311++G(3df,3pd) level of theory. It was found that in the vibrationally red-shifted complexes, hydrogen bond formation increases the anharmonic constant while in the vibrationally blue-shifted species (except FArHNe) the anharmonic constant decreases on complexation.