Temperature Dependence Kinetic Studies of the Reaction of O(3P) with CHI3 and C2H5I and the 298 K Reaction of OH(X2Π) with CHI3

A flash photolysis–resonance fluorescence technique was used to investigate the kinetics of the OH(X²Π) radical and O(³P) atom‐initiated reactions with CHI₃ and the kinetics of the O(³P) atom‐initiated reaction with C₂H₅I. The reactions of the O(³P) atom with CHI₃ and C₂H₅I were studied over the temperature range of 296 to 373 K in 14 Torr of helium, and the reaction of the OH (X²Π) radical with CHI₃ was studied at T = 298 K in 186 Torr of helium. The experiments involved time‐resolved resonance fluorescence detection of OH (A²Σ⁺ → X²Π transition at λ = 308 nm) and of O(³P) (λ = 130.2, 130.5, and 130.6 nm) following flash photolysis of the H₂O/He, H₂O/CHI₃/He, O₃/He, and O₃/C₂H₅I/He mixtures. A xenon vacuum UV (VUV) flash lamp (λ > 120 nm) served as a photolysis light source. The OH radicals were produced by the VUV flash photolysis of water, and the O(³P) atoms were produced by the VUV flash photolysis of ozone. Decays of OH radicals and O(³P) atoms in the presence of CHI₃ and C₂H₅I were observed to be exponential, and the decay rates were found to be linearly dependent on the CHI₃ and C₂H₅I concentrations. Measured rate coefficients for the reaction of O(³P) atoms with CHI₃ and C₂H₅I are described by the following Arrhenius expressions (units are cm³ s^?1): k_O+C2H5I(T) = (17.2 ± 7.4) × 10^?12 exp[?(190 ± 140)K/T] and k_O+CHI3(T) = (1.80 ± 2.70) × 10^?12 exp[?(440 ± 500)K/T]; the 298 K rate coefficient for the reaction of the OH radical with CHI₃ is k_OH+CHI3(298 K) = (1.65 ± 0.06) × 10^?11 cm³ s^?1. The listed uncertainty values of the Arrhenius parameters are 2σ‐standard errors of the calculated slopes by linear regression.     

Synthesis, crystal structure, and biological activity of the binuclear complex [Pr2(C10H9N2O4)2(C7H5O3)4(H2O)2] · 2H2O

A novel binuclear praseodymium(III) complex with N-(2-propionyl)salicyloylhydrazone (C₁₀H₁₀N₂O₄, H₃L) and p-hydroxybenzoic acid (C₇H₆O₃, Phba) was prepared in a H₂O-C₂H₅OH mixed solution, and the crystal structure of [Pr₂(H₂L)₂(Phba)₄(H₂O)₂] · 2H₂O (I) was determined by X-ray single crystal diffractometry. Complex I crystallizes in the monoclinic system, space group P2₁/c, a = 1.1050(4), b = 1.9534(7), c = 1.2376(4) ?, β = 94.955(7)°, and Z = 4. In the structure each Pr³⁺ ion lies in a single capped square antiprism geometry coordinated by carboxyl O and acyl O atoms and azomethine N atom of one ligand (H₂L⁻ form), which coordinates via the keto form, four carboxyl O atoms from two Phba, and O atoms of two water molecules. In each molecule, two tridentate ligands were coordinated by the H₂L⁻ form, and each Pr³⁺ ion was chelated by the carboxyl group from Phba. The carboxyl groups of H₂L⁻ and other two Phba were coordinated via μ₂-bridging form and bidentate bridging form, respectively. Complex I and ligands Phba and H₃L were also searched for biological activity against Valsa mali by the growth rate method. The result showed that the inhibitory rate of ligands Phba and H₃L is better than complex I, especially Phba.     

Identification of peroxo groups in supramolecular layered structures as probed by Raman spectroscopy

Peroxide-containing supramolecular structures prepared by reacting lithium aluminum layered double hydroxides (Li-Al LDHs) with concentrated hydrogen peroxide solutions were characterized by Raman spectroscopy. These compounds were formulated as [LiAl₂(OH)₆](OH) · H₂O₂ · H₂O(I) and [LiAl₂(OH)₆](OOH) · H₂O₂ · H₂O(II). The frequencies 830 and 849 cm⁻¹ in the spectra of compounds I and II were assigned to O—C stretching vibrations in two nonequivalent peroxo groups. The band at 866 cm⁻¹ in compound II was assigned to O—O vibrations in the hydroperoxo group (OOH)⁻. Proceeding from calculated strength factors, we inferred that the O—O bond in the hydroperoxo group of compound II is stronger than in the H₂O₂ solvating group. Original Russian Text ? T.A. Tripol’skaya, I.V. Pokhabova, P.V. Prikhodchenko, G.P. Pilipenko, E.A. Legurova, N.A. Chumaevskii, 2009, published in Zhurnal Neorganicheskoi Khimii, 2009, Vol. 54, No. 3, pp. 513–515.     

Kinetics of the gas-phase reactions of the OH radical with (C2H5)3PO and (CH3O)2P(S)Cl at 296 ± 2 K

The kinetics of the gas-phase reactions of the OH radical with (C₂H₅O)₃PO and (CH₃O)₂P(S)Cl and of the reactions of NO₃ radicals and O₃ with (CH₃O)₂P(S)Cl have been studied at room temperature. Using a relative rate technique, the rate constants determined for the reactions of the OH radical with (C₂H₅O)₃PO and (CH₃O)₂P(S)Cl at 296 ± 2 K and 740 torr total pressure of air were (5.53 ± 0.35) × 10^?11 and (5.96 ± 0.38) × 10^?11 cm³ molecule^?1 s^?1, respectively. Upper limits to the rate constants for the NO₃ radical and O₃ reactions with (CH₃O)₂P(S)Cl of <3 × 10^?14 cm³ molecule^?1 s^?1 and <2 × 10^?19 cm³ molecule^?1 s^?1, respectively, were obtained. These data are compared and discussed with previous literature data for organophosphorus compounds.     

Formation of O(3P) atoms and epoxides from the gas- phase reaction of O3 with isoprene

The formation yields of 1,2-epoxy-2-methyl-3-butene and 1,2-epoxy-3-methyl-3-butene have been measured from the reaction of O₃ with isoprene at room temperature and one atmosphere total pressure of N₂ and air diluents, with and without cyclohexane to scavenge the OH radicals formed in this reaction system. In addition, a relative rate method was used to determine a rate constant for the gas-phase reaction of O₃ with 1,2-epoxy-2-methyl-3-butene of (2.5 ± 0.7) x 10^-18 cm³ molecules^-1 s^-1 at 296 ± 2 K. Our data show that the epoxide yields in N₂ and air diluents are the same, with formation yields of 1,2-epoxy-2-methyl-3-butene of 0.028 ± 0.007 and of 1,2-epoxy-3-methyl-3-butene of 0.011 ± 0.004. These data further show that the epoxides arise from the primary O₃ reaction with isoprene, and not via the formation of O(³P) atoms from the O₃ - isoprene reaction followed by reaction of these O(³P) atoms with isoprene.     

EPR investigation of plasma-chemical resist etching in O2 and O2/CF4 discharges

During the etching of AZ 1350 photoresist in O₂ and O₂/CF₄ discharges, ground-state concentrations of atoms (O, F, and H), and small radicals (OH, HO₂, RO₂) were measured in the discharge afterglow by EPR spectroscopy. In the case of CF₄/O₂ discharges, the dependence of O and F atom concentrations on the etch time reflects both surfäce oxidation and fluorination reactions in accordance with existing etch models. In the case of high-rate resist etching in pure O₂ discharges, high concentrations of product radicals (H, OH and HO₂) were detected and compared with resist free O₂/H₂O discharges. Kinetic modeling of the afterglow reactions reveals that the mean lifetime and, accordingly, the diffusion length of the etchant species O(³P) is drastically reduced in rapid reactions with OH and HO₂. The results are used to simulate both etch homogeneity and the loading effect in a simple etch model.     

Kinetics of the borate anion catalyzed oxidation of diethyl sulfide with hydrogen peroxide in an <Emphasis Type="Italic">i</Emphasis>-PrOH–H<Subscript>2</Subscript>O medium

It was found that in a wide range of pH in the presence of boric acid the oxidation of diethyl sulfide (Et₂S) with hydrogen peroxide in an i-PrOH–H₂O medium occurs with the participation of H₂O₂, HOO^–, monoperoxo-(B(OH)₃OOH^–), and diperoxoborates (B(OH)₂(OOH)₂⁻). The stability constants of peroxoborates and the rate constants for the reactions of H₂O₂, HOO⁻, B(OH)₃(OOH)₂⁻, and B(OH)₂(OOH)₂⁻ with Et₂S under these conditions were determined.     

Preparation and properties of complexes of chromium(II) with some oxo-anions of phosphorus(V)

Summary Complexes of chromium(II) with diphenylphosphinate, Cr(O₂PPh₂)₂ · H₂O, diphenylphosphate Cr{O₂P(OPh)₂} · 1/2H₂O, phenylphosphinate, Cr(O₂PHPh)₂ · 2H₂O, phenyl-phosphonate, Cr(O₃PPh) · H₂O, and monofluorophosphate, Cr{O₂P(OH)F}₂ · H₂O, are high-spin. From their reflectance spectra and antiferromagnetic behaviour the last three are believed to be three-dimensional polymers with R₂PO ₂ ^– bridges in which some O atoms bridge two Cr atoms, leading to magnetic interaction. The other complexes show only weak magnetic interaction, and the reflectance spectra of Cr(O₂PPh₂)₂ and its hydrate indicate that both contain planar CrO₄ units. It is therefore believed to be a linear polymer with the Cr atoms well separated by double R₂PO ₂ ^– bridges. The reflectance spectrum of Cr{O₂P(OPh)₂}₂ suggests additional weak coordination of O atoms from adjacent polymer chains.     

Bis(citrato)hydroxogermanic(IV) acid dimer [H5O2][Ge(H2Cit)(H2.5Cit)(OH)]2 · 2CH3COOH · 2H2O: Synthesis, properties, and crystal and molecular structure

Bis(citrato)hydroxogermanic(IV) acid was obtained for the first time in the complex [H₅O₂][Ge(H₂Cit)(H_2.5Cit)(OH)]₂ · 2CH₃COOH · 2H₂O (H₄Cit is citric acid). The complex was characterized by chemical analysis, X-ray powder diffraction, TGA, and IR spectroscopy. Complex I was studied by X-ray crystallography. The crystals are triclinic; a = 10.0651(4) ?, b = 10.1918(4) ?, c = 10.5838(4) ?, α = 85.0110(10)°, β = 85.2170(10)°, γ = 86.7670(10)°, V = 1076.50(7) ?³, Z = 1, space group P[`1]P\bar 1, R1 = 0.0353 for 5709 reflections with I > 2σ(I). Complex I is composed of centrosymmetric dimeric complex anions [Ge₂(H₂Cit)₂(H_2.5Cit)₂(OH)₂]⁻, dioxonium cations [H₅O₂]⁺, and acetic acid and water molecules of crystallization. The coordination polyhedron of the Ge atom is a trigonal bipyramid. Its equatorial plane comprises two O atoms of the deprotonated alcohol groups of two ligands H₂Cit (A) and H_2.5Cit (B) and the O atom of the terminal OH group (Ge-O, 1.7585–1.7754 ?; O_eqGe(1)O_eq, 116.26°–127.64°). The axial positions are occupied by the carboxy O atom of the deprotonated carboxylate group of the α branch of ligand A (α-Ge-O(C)(carb), 1.8882(12) ?)) and the carbonyl O atom of the hemiprotonated acetate α branch of ligand B (α-Ge-O(C) 1.9615(12) ?, O(1)Ge(1)O(8) 170.47(5)°). In structure I, the complex dianion, the cation, and acetic acid and water molecules are united through hydrogen bonds into a three-dimensional framework.     

Heteropoly Complexes Na0.5Cs2 ? x[H0.5 ? xM

Crystals of novel heterepoly complexes (HPC) Na_0.5Cs_{2 − x} [H_{0.5 − x} M _x ^II X^III(OH)₆Mo₆O₁₈] · 7−8H₂O (M^II = Fe, Mn; X^III = Cr, Al) are synthesized. Crystal structures of the complexes Na_0.5Cs_{2 − x} [H_{0.5 − x} Fe_xCr(OH)₆Mo₆O₁₈] · 7H₂O (I) (x = 0.19) and Na_0.5Cs_{2 − x} [H_{0.5 − x} Mn_xAl(OH)₆Mo₆O₁₈] · 8H₂O (II) (x = 0.22) are determined (space group Pbcn, Z = 8, a = 23.023(4) Å, b = 22.064(4) Å, c = 11.606(3) Å, V = 5895.66 ų for I and a = 22.972(9) Å, b = 22.002(8) Å, c = 11.543(5) Å, V = 5834.18 ų for II, respectively). The [X^III(OH)₆Mo₆O₁₈]³⁻ ligands were found to be coordinated in monodentate fashion to M atoms due to the participation of a terminal O atom of the cis-MoO₂ group in coordination with the Fe and Mn atoms, which was confirmed by IR data. __________ Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 9, 2005, pp. 663–676. Original Russian Text Copyright ? 2005 by Gavrilova, Molchanov.     

The QCT calculation of the rate constants for the N(4S)+O2(X3Σ g ? ) →NO(X2Π)+O(3P) reaction

A quasi-classical trajectory (QCT) calculation with the fourth-order explicit symplectic algorithm for the N(⁴S) + O₂(X³Σ_g⁻) → NO(X²Π) + O(³P) reaction has been performed by employing the ground and first-excited potential energy surfaces (PESs). Since the translational temperature considered is up to 5000 K, the larger relative translational energy and the higher vibrational and rotational level of O₂ molecule have been taken into account. The affect of the relative translational energy, the vibrational and rotational level of O₂ molecule in the reaction cross-sections of the ground and first-excited PESs has been discussed in a extensive range. And we exhibit the dependence of microscopic rate constants on the vibrational and rotational level of O₂ molecule at T = 4000 K. The thermal rate constants at the translational temperature betweem 300 and 5000 K have been evaluated and the corresponding Arrhenius curve has been fitted for reaction (1). It is found by comparison that the thermal rate constants determined in this work have a better agreement with the experimental data and provide a more valid theoretical reference.     

Syntheses and crystal structures of two new hydrated borates, Zn8[(BO3)3O2(OH)3] and Pb[B5O8(OH)]·1.5H2O

Two new hydrated borates, Zn₈[(BO₃)₃O₂(OH)₃] and Pb[B₅O₈(OH)]·1.5H₂O, have been prepared by hydrothermal reactions at 170 °C. Single-crystal X-ray structural analyses showed that Zn₈[(BO₃)₃O₂(OH)₃] crystallizes in a non-centrosymmetric space group R32 with a=8.006(2) Å, c=17.751(2) Å, Z=3 and Pb[B₅O₈(OH)]·1.5H₂O in a triclinic space group P1¯ with a=6.656(2) Å, b=6.714(2) Å, c=10.701(2) Å, α=99.07(2)°, β=93.67(2)°, γ=118.87(1)°, Z=2. Zn₈[(BO₃)₃O₂(OH)₃] represents a new structure type in which Zn-centered tetrahedra are connected via common vertices leading to helical ribbons _∞¹[Zn₈O₁₅(OH)₃]¹⁷⁻ that pack side by side and are further condensed through sharing oxygen atoms to form a three-dimensional _∞³[Zn₈O₁₁(OH)₃]⁹⁻ framework. The boron atoms are incorporated into the channels in the framework to complete the final structure. Pb[B₅O₈(OH)]·1.5H₂O is a layered compound containing double ring [B₅O₈(OH)]²⁻ building units that share exocyclic oxygen atoms to form a two-dimensional layer. Symmetry-center-related layers are stacked along the c-axis and held together by interlayer Pb²⁺ ions and water molecules via electrostatic and hydrogen bonding interactions. The IR spectra further confirmed the existence of both triangular BO₃ and OH groups in Zn₈[(BO₃)₃O₂(OH)₃], and BO₃, BO₄, OH groups as well as guest water molecules in Pb[B₅O₈(OH)]·1.5H₂O.     

Mechanism of hydroquinone-inhibited oxidation of acrylic acid and methyl methacrylate

The kinetics of hydroquinone-inhibited oxidation of acrylic acid and methyl methacrylate was studied volumetrically by measuring the oxygen uptake in the presence of an initiator (azobisisobutyronitrile) at T = 333 K and P _{O 2} = 1 and 0.21 atm. The oxidation of acrylic acid inhibited by 4-methoxyphenol was studied under the same conditions for comparison. The rate constants of the reactions of the peroxyl radicals of acrylic acid (∼CH₂CH(COOH)O₂^·) and methyl methacrylate (∼CH₂CMe(COOMe)O₂^·) with hydroquinone (HOC₆H₄OH) (1.20 × 10⁵ and 7.16 × 10⁴ l mol⁻¹ s⁻¹, respectively) and of the reaction of peroxyl radicals of acrylic acid with 4-methoxyphenol (p-CH₃OC₆H₄OH) (3.25 × 10⁴ l mol⁻¹ s⁻¹) were measured. The stoichiometric inhibition factors f were determined. The reaction between the semiquinone radical and oxygen, O₂ + HOC₆H₄O^·, plays an important role, decreasing the factor f and the efficiency of the inhibition effect of hydroquinone. The rate constants of this reaction were calculated from kinetic data: k = 5.72 × 10² (in acrylic acid) and 4.60 × 10² l mol⁻¹ s⁻¹ (in methyl methacrylate).     

Stationary points on the energy hypersurface of the reaction O3 + H•→ [•O3H]* ⇆ O2 + •OH and thermodynamic functions of •O3H at G3MP2B3, CCSD(T)-CBS (W1U) and MR-ACPF-CBS levels of theory

The relative enthalpies, ΔH^o (0) and ΔH^o (298.15), of stationary points (four minimum and three transition structures) on the ^•O₃H potential energy surface were calculated with the aid of the G3MP2B3 as well as the CCSD(T)–CBS (W1U) procedures from which we earlier found mean absolute deviations (MAD) of 3.9 kJ mol⁻¹ and 2.3 kJ mol⁻¹, respectively, between experimental and calculated standard enthalpies of the formation of a set of 32 free radicals. For CCSD(T)-CBS (W1U) the well depth from O₃ + H^• to trans-^•O₃H, ΔH^o_well(298.15) = −339.1 kJ mol⁻¹, as well as the reaction enthalpy of the overall reaction O₃ + H^•→O₂ + ^•OH, Δ_rH^o(298.15) = −333.7 kJ mol⁻¹, and the barrier of bond dissociation of trans-^•O₃H → O₂ + ^•OH, ΔH^o(298.15) = 22.3 kJ mol⁻¹, affirm the stable short-lived intermediate ^•O₃H. In addition, for radicals cis-^•O₃H and trans-^•O₃H, the thermodynamic functions heat capacity C^o_p(T), entropy S^o (T), and thermal energy content H^o(T) − H^o(0) are tabulated in the range of 100 − 3000 K. The much debated calculated standard enthalpy of the formation of the trans-^•O₃H resulted to be Δ_fH^o(298.15) = 31.1 kJ mol ⁻¹ and 32.9 kJ mol ⁻¹, at the G3MP2B3 and CCSD(T)-CBS (W1U) levels of theory, respectively. In addition, MR-ACPF-CBS calculations were applied to consider possible multiconfiguration effects and yield Δ_fH^o(298.15) = 21.2 kJ mol ⁻¹. The discrepancy between calculated values and the experimental value of −4.2 ± 21 kJ mol⁻¹ is still unresolved. Note added in proof: Yu-Ran Luo and J. Alistair Kerr, based on the discussion in reference 12, recently presented an experimental value of Δ_fH^o(298.15) = 29.7 ± 8.4 kJ mol⁻¹ in the 85th edition of the CRC Handbook of Chemistry and Physics (in progress).     

非晶态镍硼酸盐结构的EXAFS研究

由摩尔比分别为1:2和1:8的NiCl₂·6H₂O和Na₂B₄O₇·10H₂O作为反应物, 合成两种非晶态镍硼酸盐, 同时通过水热法合成β-Ni(OH)₂. 化学分析和热重-微商热重法(TG-DTG)分析结果确定两种非晶态镍硼酸盐的分子组成分别为NiO·0.8B₂O₃·4.5H₂O和NiO·B₂O₃·3H₂O. 激光拉曼(Raman)实验结果表明镍硼酸盐样品中主要存在的硼氧阴离子为B₃O₃(OH)₅^2-和B₂O(OH)₆^2-. 同步辐射扩展X射线吸收精细结构(EXAFS)方法对样品进行结构解析, 通过数据拟合给出样品中Ni 原子周围近邻配位原子种类、配位数以及原子间距离. 用不同晶体结构作为标准对两种非晶态镍硼酸盐进行拟合的结果表明, 样品中Ni 原子周围局域结构与Ni₃B₂O₆晶体(ICSD No.31387)中的吻合较好. Ni 原子周围配位原子为O、B和Ni, 对于NiO·0.8B₂O₃·4.5H₂O, 配位数分别为5.7、3.8和3.8, 配位距离分别为0.208、0.263 和0.311 nm; 对于NiO·B₂O₃·3H₂O, 配位数分别为6.0、4.0 和4.0, 配位距离分别为0.207、0.262和0.310 nm.     

Theoretical study of the structure and stability of the dimers of heme analogues (MC34H32N4O4)2 and their ions (MC34H32N4O4) 2+ with 3 d -metal atoms M

The electronic and geometric structures and the energetic characteristics of a series of monomeric MC₃₄H₃₂N₄O ₄ ^0,+ and dimeric (MC₃₄H₃₂N₄O₄) ₂ ^0,+ molecules, heme analogues and their positively charged ions with 3d-metal atoms M = Ti, V, Cr, and Mn, have been calculated by the density functional theory B3LYP method with the Gen−1 = 6−31G^*(Fe) + 6−31G(C, H, N, O) and Gen−2 = 6−311+G^*(Fe) + 6−31G^*(C, H, N, O) basis sets. The computation results are compared with the analogous calculated data on the heme dimers (heme) ₂ ^0,+ . Computations show that for the (MC₃₄H₃₂N₄O₄) ₂ ^0,+ dimers, high-spin states are preferable. In these dimers, the rings are linked with each other by a pair of M-carbonyl bridges M⋯O_b=C(OH) and a pair of hydrogen bridges OH_b⋯N. The calculated energies of dissociation D of the dimers into monomers point to a rather high stability of the dimers at the beginning of the 3d series (D ∼ 2.3–3.6 eV for M = Ti, V), which decreases rapidly as the atomic number of M increases (D ∼ 0.5 eV for M = Cr and ∼0.4 eV for (heme)₂). The positive ions (MC₃₄H₃₂N₄O₄) ₂ ⁺ are ∼0.8–1.0 eV are more stable to dissociation than their neutral congeners (MC₃₄H₃₂N₄O₄)₂. The trends in the behavior of the energetic and structural characteristics of the dimers (distances R(M—N), displacements of M atoms from the porphyrin ring plane, parameters of the carbonyl and hydrogen bridges, character of ring distortions, etc.), as well as in the spin density distribution between the metal atoms and the rings in the monomers MC₃₄H₃₂N₄O₄ and dimers (MC₃₄H₃₂N₄O₄)₂ caused by their ionization and going along the 3d series, are examined. In the mixed dimer (FeC₃₄H₃₂N₄O₄)(VC₃₄H₃₂N₄O₄), the rings are linked by only one strong carbonyl bridge V⋯O_b=C(OH), with some contribution made by the neighboring hydrogen bridge. The dissociation energy of this mixed dimer into monomers is close to a half of the dissociation energy of the “symmetric” dimer (VC₃₄H₃₂N₄O₄)₂. Original Russian Text ? O.P. Charkin, N.M. Klimenko, D.O. Charkin, S.H. Lin, 2007, published in Zhurnal Neorganicheskoi Khimii, 2007, Vol. 52, No. 8, pp. 1332–1346.     

Hydrogen bonded H3O, H2O, HF, F in fluoride metalates (Al, Cr, Fe, Zr, Ta) templated with tren (tris-(2-aminoethyl)amine)

The environment of H₃O⁺, H₂O, HF and F⁻ species (non-bonded to metals) is considered in fluoride metalates which crystallise from the (Al(OH)₃, Cr(OH)₃, FeF₃, ZrF₄, Ta₂O₅)-tren-HF_aq·-ethanol systems (microwave heating at 190 °C during 1 h). The presence of (H₃O)(H₂O)₆⁺ clusters or H₃O⁺ cations, of isolated or associated H₂O molecules, of (HF₂)⁻ and F⁻ anions is evidenced. The thermal stability of the solids depends strongly on the nature of the hydrogen-bonded species associated with the preceding cations or anions and on the formation of water ribbons or layers.     

磷酸铁锂废料中FePO4·2H2O提取及其杂质形成机理

采用化学共沉淀方法从磷酸铁锂废料中提取FePO₄·2H₂O,并研究了回收过程中杂质形成的机理。在热力学计算基础上绘制了298和363 K时Fe-P-Li-H₂O体系的电势(φ)-pH图,结果表明当pH≤5.0时,Fe(OH)₃相可以自发地转成FePO₄·2H₂O相,从而得到高纯的FePO₄·2H₂O。但实验结果发现当溶液中铁、磷的物质的量之比(n_Fe∶n_P)为1∶1,合成pH为1.5～2.2时得到的FePO₄·2H₂O中存在Fe(OH)₃杂质,这是因为在共沉淀过程中少量Fe³⁺以Fe(OH)₃快速沉淀,而陈化时Fe(OH)₃相转化速率慢,因此FePO₄·2H₂O中含有Fe(OH)₃     

New technique for generating high concentrations of gaseous OH radicals in relative rate measurements

We have developed a technique for generating high concentrations of gaseous OH radicals in a reaction chamber. The technique, which involves the UV photolysis of O₃ in the presence of water vapor, was used in combination with the relative rate method to obtain rate constants for reactions of OH radicals with selected species. A key improvement of the technique is that an O₃/O₂ (3%) gas mixture is continuously introduced into the reaction chamber, during the UV irradiation period. An important feature is that a high concentration of OH radicals [(0.53–1.2) × 10¹¹ radicals cm^?3] can be produced during the irradiation in continuous, steady‐state experiment. Using the new technique in conjunction with the relative rate method, we obtained the rate constant for the reaction of CHF₃ (HFC‐23) with OH radicals, k₁. We obtained k₁(298 K) = (3.32 ± 0.20) × 10^?16 and determined the temperature dependence of k₁ to be (0.48 ± 0.13) × 10^?12 exp[?(2180 ± 100)/T] cm³ molecule^?1 s^?1 at 253–328 K using CHF₂CF₃ (HFC‐125) and CHF₂Cl (HCFC‐22) as reference compounds in CHF₃–reference–H₂O gas mixtures. The value of k₁ obtained in this study is in agreement with previous measurements of k₁. This result confirms that our technique for generating OH radicals is suitable for obtaining OH radical reaction rate constants of ～10^?16 cm³ molecule^?1 s^?1, provided the rate constants do not depend on pressure. In addition, it also needed to examine whether the reactions of sample and reference compound with O₃ interfere the measurement when selecting this technique. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 317–325, 2003     

Theoretical Studies on Mechanism and Rate Constant of Gas Phase Hydrolysis of Glyoxal Catalyzed by Sulfuric Acid

The gas phase hydration of glyoxal (HCOCHO) in the presence of sulfuric acid (H2SO4) were studied by the high-level quantum chemical calculations with M06-2X and CCSD(T) theoretical methods and the conventional transition state theory (CTST). The mechanism and rate constant of the ve di erent reaction paths are consid-ered corresponding to HCOCHO+H₂O, HCOCHO+H₂O H₂O, HCOCHO H₂O+H₂O, HCOCHO+H₂O H₂SO₄ and HCOCHO H₂O+H₂SO₄. Results show that H₂SO₄ has a strong catalytic ability, which can signi cantly reduce the energy barrier for the hydration reaction of glyoxal. The energy barrier of hydrolysis of glyoxal in gas phase is lowered to 7.08 kcal/mol from 37.15 kcal/mol relative to pre-reactive complexes at the CCSD(T)/6-311++G(3df, 3pd)//M06-2X/6-311++G(3df, 3pd) level of theory. The rate constant of the H₂SO₄ catalyzed hydrolysis of glyoxal is 1.34×10^-11cm³/(molecule s), about 10¹³ higher than that involving catalysis by an equal number of water molecules, and is greater than the reaction rate of glyoxal reaction with OH radicals of 1.10×10^-11cm³/(molecule s) at the room temperature, indicating that the gas phase hydrolysis of glyoxal of H₂SO₄ catalyst is feasible and could compete with the reaction glyoxal+OH under certain atmospheric condi-tions. This study may provide useful information on understanding the mechanistic features of inorganic acid-catalyzed hydration of glyoxal for the formation of oligomer