Energy partitioning in the reaction O(1D) + H2O → OH + OH.: The influence of O(1D) translational energy on the reaction rate constant

For the exothermic reaction O (¹D) + H₂O → OH + OH the rate constant and its energy dependence were determined by monitoring the concentration of the OH product. This was done by integrating the distribution of product molecules over all accessible states. The rate constant, determined at different velocity distributions of the reacting metastable over a wide range, is energy independent.     

Vibrational excitation of OH(X2Π) produced in the reaction of O(1D) with H2

A lower limit to the OH(X²Π) vibrational excitation produced by the reaction O(¹D) + H₂ has been observed using a low-pressure infrared chemiluminescence apparatus. The O(¹D) was generated by laser photolysis of O₃. The measured OH(v') vibrational distribution is inverted; it peaks at v' = 2.     

The reaction of OH with NO2 and the deactivation of O(1D) by CO

NO₂ was photolyzed with 2288 Å radiation at 300° and 423°K in the presence of H₂O, CO, and in some cases excess He. The photolysis produces O(¹D) atoms which react with H₂O to give HO radicals or are deactivated by CO to O(³P) atoms The ratio k₅/k₃ is temperature dependent, being 0.33 at 300°K and 0.60 at 423°K. From these two points, the Arrhenius expression is estimated to be k₅/k₃ = 2.6 exp(?1200/RT) where R is in cal/mole – °K. The OH radical is either removed by NO₂ or reacts with CO The ratio k₂/k^α is 0.019 at 300°K and 0.027 at 423°K, and the ratio k₂/k⁰ is 1.65 × 10^?5M at 300°K and 2.84 × 10^?5M at 423°K, with H₂O as the chaperone gas, where k^α = k₁ in the high-pressure limit and k⁰[M] = k₁ in the low-pressure limit. When combined with the value of k₂ = 4.2 × 10⁸ exp(?1100/RT) M^?1sec^?1, k^α = 6.3 × 10⁹ exp (?340/RT)M^?1sec^?1 and k⁰ = 4.0 × 10¹²M^?2sec^?1, independent of temperature for H₂O as the chaperone gas. He is about 1/8 as efficient as H₂O.     

The reaction of O(3P) with H2O2

The rate constant for the reaction of O(³P) with H₂O₂ was measured as a function of temperature and the [H₂O₂]₀/[O]₀ ratio. The numerical solution of the appropriate rate equations was used to arrive at a mechanism which adequately describes our results and the rather divergent data in the literature. A recommended expression for the temperature dependence of the absolute rate constant is presented from consideration of the available experimental data.     

Products of the gas-phase reactions of OH radicals with (C2H5O)2P(S)CH3 and (C2H5O)3PS

Products of the gas-phase reactions of OH radicals with O,O-diethyl methylphosphonothioate [(C2H5O)2P(S)CH3, DEMPT] and O,O,O-triethyl phosphorothioate [(C2H5O)3PS, TEPT] have been investigated at room temperature and atmospheric pressure of air using in situ atmospheric pressure ionization mass spectrometry (API-MS) and, for the TEPT reaction, gas chromatography and in situ Fourier transform infrared (FT-IR) spectroscopy. Combined with products quantified previously by gas chromatography, the products observed were: from the DEMPT reaction, (C2H5O)2P(O)CH3 (21+/-4% yield) and C2H5OP(S)(CH3)OH or C2H5OP(O)(CH3)SH (presumed to be C2H5OP(O)(CH3)SH by analogy with the TEPT reaction); and from the TEPT reaction, (C2H5O)3PO (54-62% yield), SO2 (67+/-10% yield), CH3CHO (22-40% yield) and, tentatively, (C2H5O)2P(O)SH. The FT-IR analyses showed that the formation yields of HCHO, CO, CO2, peroxyacetyl nitrate [CH3C(O)OONO2], organic nitrates, and acetates from the TEPT reaction were <5%, 3+/-1%, <7%, <2%, 5+/-3%, and 3+/-2%, respectively. Possible reaction mechanisms are discussed.     

Theoretical study for the CH3C(O)(CH2)2OH + OH reaction

The mechanisms and the kinetics of the OH radical reaction with 4-hydroxy-2-butanone (4H2B) are investigated theoretically. Five hydrogen-abstraction channels are identified for the title reaction. The first potential energy profile of the title reaction is presented. The rate constants for each reaction channel are evaluated using transition state theory method in the temperature range of 200–1,000 K. Branching ratio of the title reaction is calculated and plotted. It is shown that the “in-plane hydrogen abstraction” from the methoxy end is the dominant channel, and the other hydrogen-abstraction channels play the minor role. The comparison between theoretical and experimental results is discussed. The three-parameter Arrhenius expression for the rate constants is also provided.     

Molecular and crystal structures of Ph2P(O)(CH2)2OH and Ph2P(O)CH2(C6H6)OH

The molecular and crystal structures of Ph₂P(O)(CH₂)₂OH and Ph₂P(O)CH₂(C₆H₆)OH have been determined. For the first compound the space group is with unit cell dimensions a=10.505(2), b=13.720(2), c=14.782(3) Å; =72.58(6), =76.95(6), =72.49(6)° for Z=6 (Syntex diffractometer,MoK radiation, 2996 reflections, R=3.2%). The second compound crystallizes in the space group P2₁2₁2₁ with unit cell dimensions a=9.371(3), b=9.014(3), c=18.461(5) Å for Z=4 (DAR-UM diffractometer,CuK radiation, 909 reflections, R=4.9%). In Ph₂P(O)(CH₂)₂OH, three independent molecules differing in structural details are linked by the P=O...O hydrogen bonds (O...H is 1.84, 1.80, and 1.86 Å), to form a chain. In Ph₂P(O)CH₂(C₆H₆)OH, the molecules are joined by pairs of the P=O...H–O bonds (O...H is 1.81 Å) to form 16-membered dimeric associates.Institute of Chemical Physics, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 34, No. 3, pp. 109–118, May–June 1993.Translated by T. Yudanova     

The dimeric unit [La(H2O)4(m-PO3C6H4COOH)(m-PO2(OH)C6H4COOH)(m-PO(OH)2C6H4COOH)]2 as building block of layered hybrid material

A new hybrid organic–inorganic material with the structural formula unit [La(H₂O)₄(m-PO₃C₆H₄COOH)(m-PO₂(OH)C₆H₄COOH)(m-PO(OH)₂C₆H₄COOH)]₂ (or [La(H₂O)₄C₂₁H₁₈O₁₅P₃]₂) has been synthesized under hydrothermal condition from La(NO₃)₃·6H₂O and 3-phosphonobenzoic acid (m-PO(OH)₂–C₆H₄–COOH) which is a rigid organic precursor possessing two types of functional groups: phosphonic acid and carboxylic acid. The two units of the produced hybrid are linked together by hydrogen bonds leading to a layered framework composing of by a repetition of inorganic and organic slices. The organic layers consist of dimeric units made of two meta-phosphono-benzoic acid linked together by hydrogen bonds involving their COOH groups. Two kinds of dimeric units are observed: PO₃C₆H₄COOH?HOOCC₆H₄PO(OH)₂, present 2 times in the structure, and PO₂(OH)C6H4COOH?HOOCC₆H₄PO₂(OH). The material crystallises in a monoclinic cell (C2/c (15) space group) with the following parameters: a = 42.515(4) Å, b = 7.4378(6) Å, c = 20.307(2) Å, β = 118.031(6)°, V = 5668.2(9) Å³, Z = 4, density = 1.908 g/cm³.     

OH stretch IR spectra of (H2O)3 and benzene-(H2O)3

The OH stretch IR spectrum of (H₂O)₃ is significantly altered upon complexation of the cluster with a benzene molecule. Theoretical calculations show that the differences in the OH stretch spectra of (H₂O)₃ and benzene-(H₂O)₃ are primarily due to mode localization induced by the benzene molecule. Received: 27 January 1997 / Accepted: 28 January 1997     

Synthesis and Crystal Structure of [VO2（C17H11N3O2） ] [VO （C4H13N3）（C6H5N3O） ]（C2H5OH）

The reaction of VO（acac）2 with 2-hydroxyl-1-naphthaldehyde isonicotinyl hydrazone and amines （ethylenediamine or diethylenetriamine） in CH3OH yields crystals of novel vanadium compounds characterized by IR, NMR spectroscopic methods and X-ray single-crystal structure determination. Two different vanadium units exist in the crystal cell of [VO2（C17H11N3O2）][VO- （C4H13N3）（C6H5N3O）]（C2H5OH） which crystallizes in the triclinic system, space group P1 with a = 8.0104（17）, b = 13.898（3）, c = 14.955（3）A, α = 89.103（4）, β = 79.551（4）, γ = 78.352（4）°, V = 1603.3（6）A^3, Mr = 723.54, Dc = 1.499 g/cm^3, Z = 2, λ（MoKα） = 0.71073 ]A,μ= 0.644 mm^-1, F（000） = 748, the final R = 0.0547 and wR = 0.0997 for 8920 observed reflections with I 〉 2σ（I）. According to structure analysis, two different molecules are arranged in the lattice and the two vanadium atoms adopt octahedral and square pyramidal coordination geometries, respectively. The interactions between DNA and vanadium complexes have been investigated by UV-Vis absorption spectro- photometry.     

Potential surfaces and dynamics of the O(3P)+H2O(X1A1)-->OH(X2pi)+OH(X2pi) reaction

We present global potential energy surfaces for the three lowest triplet states in O(3P)+H2O(X1A1) collisions and present results of classical dynamics calculations on the O(3P)+H2O(X1A1)-->OH(X2pi)+OH(X2pi) reaction using these surfaces. The surfaces are spline-based fits of approximately 20,000 fixed geometry ab initio calculations at the complete-active-space self-consistent field+second-order perturbation theory (CASSCF+MP2) level with a O(4s3p2d1f)/H(3s2p) one electron basis set. Computed rate constants compare well to measurements in the 1000-2500 K range using these surfaces. We also compute the total, rovibrationally resolved, and differential angular cross sections at fixed collision velocities from near threshold at approximately 4 km s(-1) (16.9 kcal mol(-1) collision energy) to 11 km s(-1) (122.5 kcal mol(-1) collision energy), and we compare these computed cross sections to available space-based and laboratory data. A major finding of the present work is that above approximately 40 kcal mol(-1) collision energy rovibrationally excited OH(X2pi) products are a significant and perhaps dominant contributor to the observed 1-5 micro spectral emission from O(3P)+H2O(X1A1) collisions. Another important result is that OH(X2pi) products are formed in two distinct rovibrational distributions. The "active" OH products are formed with the reagent O atom, and their rovibrational distributions are extremely hot. The remaining "spectator" OH is relatively rovibrationally cold. For the active OH, rotational energy is dominant at all collision velocities, but the opposite holds for the spectator OH. Summed over both OH products, below approximately 50 kcal mol(-1) collision energy, vibration dominates the OH internal energy, and above approximately 50 kcal mol(-1) rotation is greater than vibrational energy. As the collision energy increases, energy is diverted from vibration to mostly translational energy. We note that the present fitted surfaces can also be used to investigate direct collisional excitation of H2O(X1A1) by O(3P) and also OH(X2pi)+OH(X2pi) collisions.     

H2 formation in the reaction of O(1D) with CH4

The reaction of O(¹D) with CH₄ was studied to determine the efficiency of H₂ production in a direct process, and it was found to be 0.11 ± 0.02. Thus the two channels which account for all of the reaction between O(¹D) and CH₄ in the gas phase are      

Syntheses and crystal structures of [Na(H2O)](C17H13O6SO3)* 2H2O and [NKH2O)6]C17H13O6SO3)2*H2O

Two hydrates of sodium 5,7‐dihydroxy‐6,4′‐dimethoxyisoflavone‐3′‐sulfonate ([Na(H₂O)J(C₁₇H₁₃O₆SO₃)*2H₂O,] 1) and nickel 5,7‐dihydroxy‐6,4′‐dimethoxyisoflavone‐3′‐sulfonate ([Ni(H₂O)₆](C₁₇H₁₃O₆SO₃)₂*4H₂O, 2) were synthesized and characterized by IR, 'H NMR and X‐ray diffraction analyses. The hydrate 1 crystallizes in the mono‐clinic system, space group P2(1) with a=0.8201(9) nm, b=0.8030(8) nm, c= 1.5361(16) nm, β=102.052(12)°, V =0.9893(18) nm³, D,= 1.579 g/cm³, Z=2, μ=0.252 nm^?1, F(000)=488, R=0.0353, wR=0.0873. The hydrate 2 belongs to triclinic system, space group P‐1 with a=0.7411(3) nm, b=0.8333(3) nm, c=1.7448(7) nm, α= 86.361(6)°, β=86.389(5)°, γ= 88.999(3)°, V=1.0731(7) nm³, D,=1.587 g/cm³, Z=1, μ=0.649 m^?1, F(000)= 534. In the structure of 1, the sodium cation is coordinated by six oxygen atom and two adjacent ones are bridged by three oxygen atoms to form an octahedron chain. The C? H…?… hydrogen bonds exist between two isoflavone molecules in the structure of 2. Meanwhile, hydrogen bonds in two compounds, link themselves to assemble two three‐dimensional network structures, respectively.     

Mechanisms for the deamination reaction of cytosine with H2O/OH(-) and 2H2O/OH(-): a computational study

Mechanisms for the deamination reaction of cytosine with H 2O/OH (-) and 2H 2O/OH (-) to produce uracil were investigated using ab initio calculations. Optimized geometries of reactants, transition states, intermediates, and products were determined at MP2 and B3LYP using the 6-31G(d) basis set and at B3LYP/6-31+G(d) levels of theory. Single point energies were also determined at MP2/G3MP2Large and G3MP2 levels of theory. Thermodynamic properties (Delta E, Delta H, and Delta G), activation energies, enthalpies, and free energies of activation were calculated for each reaction pathway investigated. Intrinsic reaction coordinate (IRC) analysis was performed to characterize the transition states on the potential energy surface. Seven pathways for the deamination reaction were found. All pathways produce an initial tetrahedral intermediate followed by several conformational changes. The final intermediate for all pathways dissociates to product via a 1-3 proton shift. The activation energy for the rate-determining step, the formation of the tetrahedral intermediate for pathway D, the only pathway that can lead to uracil, is 115.3 kJ mol (-1) at the G3MP2 level of theory, in excellent agreement with the experimental value (117 +/- 4 kJ mol (-1)).     

The reaction of O(3P) with C2HCl3

The reaction of O(³P), prepared from the Hg photosensitization of N₂O, with C₂HCl₃ was studied at 25°C. The products of the reaction in the absence of O₂ were CO, CHCl₃, and polymer (as well as N₂ from the N₂O). The quantum yields of CO and CHCl₃ were 0.23 ± 0.01 and 0.14 ± 0.05, is respectively independent of reaction conditions. The reaction mechanism is with k_14a/k₁₄ = 0.23, where k_14a + k_14b. Most of the HCl and CCl₂ combine to form CHCl₃, but some other products must also be formed to account for the difference in the CO and CHCl₃ quantum yields. The C₂HCl₃O* adduct polymerizes without involving additional C₂HCl₃ molecules, since the quantum yield of C₂HCl₃ disappearance, ? Φ{C₂HCl₃}, was about 1.0 at high values of [N₂O]/[C₂HCl₃]. The rate coefficient for the reaction of O(³P) with C₂HCl₃ is 0.10 that for the reaction of O(³P) with C₂F₄. In the presence of O₂ the free radical chain oxidation occurs because of the reaction The main product is CHCl₂CCl(O) with smaller amounts of CO and CCl₂O, and some CO₂. The chain lengths were long and values of ? Φ {C₂HCl₃} up to 90 were observed.