Kinetics of oxidation of dioxanes by ozone in aqueous solutions

The kinetics of oxidation of dioxanes by ozone was investigated by a spectrophotometric method in the temperature interval of 281-311 K. The activation parameters of the reaction were determined.     

Kinetics of oxidation of diols by ozone in aqueous solution

The kinetics of the oxidation of diols by ozone was investigated by a spectrophotometric method in the temperature interval of 277–304 K. The activation parameters of the reaction were determined.     

Chemiluminescence in the reaction of ozone with 1,3-dioxans in aqueous solutions

Chemiluminescence in the visible part of spectrum is found to assist the oxidation of substituted 1,3-dioxans by ozone in aqueous media. The kinetics of the chemiluminescence decay was studied in the temperature interval 323-353 K, and the activation parameters of this process were determined. A kinetic scheme is proposed to explain the results. This revised version was published online in August 2006 with corrections to the Cover Date.     

Stratospheric ozone dynamics according to the Chapman mechanism

The photochemical mechanisms behind the ozone dynamics in the stratosphere have been studied for a long time. Though the differential equations describing the kinetics associated with them are well known, their mathematical properties have not been fully explored. In this work some of these mathematical properties as well as their physical implications are investigated in the simplest photochemical mechanism, namely, Chapman’s one.     

Dynamics and mechanism of the interaction of graphite powders with ozone

The kinetics of ozone sorption by powders of finely milled graphite at 20 °C, the behavior of unpaired electrons of the conjugated systems of the structure, and the IR spectra of the surface functional groups were studied. The surface hexagonal cells enter into the reaction. After 1/6 of the accessible cells was consumed, the reaction rate decreased appreciably, most likely, due to the induction effects of the functional groups formed. Considerable weight losses of the samples were observed during the reaction. The changes in the character of the ESR spectra indicate a decrease in the sizes of the conjugation ensembles. The reaction of ozone with the surface produces local sites of structure destruction, which decrease the reactivity of the adjacent surface regions and thus protect them from further destruction. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1772–1776, September, 2008.     

Reaction products and mechanism of the regioselective oxidation of N-phenylmorpholine by ozone

The regioselective oxidation of N-phenylmorpholine by ozone in dichloromethane or acetonitrile produced a lactam and a diformylderivative. These products derive from the selective attack of ozone at the heterocyclic ring in one of the two non-equivalent reactive carbons. The reaction mechanism has been investigated by DFT calculations, which show that the reaction occurs through the insertion of ozone at the carbon–hydrogen bond of a methylene group of the morpholine ring. The regioselectivity is due to the significantly lower energy barrier calculated for the attack of ozone α to nitrogen than α to oxygen. In addition, the energy barrier decreases with increasing the polarity of the solvent, explaining the higher conversions observed for the reaction carried out in acetonitrile than in dichloromethane.     

Kinetics and mechanism of aqueous oxidation of H2S by Fe+3

The reaction kinetics of aqueous oxidation of H₂S by Fe⁺³ is investigated at 25°C by spectrophotometric method. The study conducted at various reactant concentrations and pH revealed that the reaction proceeds according to complex‐series reactions involving polysulfides as intermediates. The reaction of each step is first order with respect to Fe⁺³ and hydrogen sulfide or polysulfide. A mechanism is proposed, involving sulfido and polysulfido radicals. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 331–335, 1999     

Red and green chemiluminescence of Na, Mg, and lanthanide triphenylmethyl derivatives during oxidation by dioxygen and cerium(IV)

Chemiluminescence (CL) of triphenylmethyl organometallics (TPM), Ph₃CNa, Ph₃CMgCl, and Ph₃CLnCl₂ (Ln=Cd, Eu, and Dy), in THF and toluene during oxidation by O₂ and the (NH₄)₂Ce(NO₃)₆ complex was found. The first CL is caused by the luminescence of two emitters: (Ph₃C)^*, emitting in the green spectral region (λ_max=524, 550 nm), and an unstable product of substitution of the hydrogen atom in the phenyl ring of the Ph₃C radical, emitting in the red region (λ_max=580±20 nm). The emitter of the second CL, Ph₃C^.*, is generated in the elementary electron transfer from the Ph₃C⁻ anion to Ce^IV, reducing the latter to Ce^III. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1102–1105, June, 1999.     

Fe3+-H2O2-二氯荧光素化学发光体系测定药物中的扑热息痛

酸性介质中,Fe3+催化H2O2分解生成羟基自由基,进而氧化扑热息痛产生微弱的化学发光,二氯荧光素对该发光强度有较强的增敏作用。研究了影响化学发光强度的各种因素,并探讨了其可能的发光机理。在最佳化学发光条件下,其化学发光强度与扑热息痛的浓度在8.0×10-8～5.0×10-5mol/L范围内呈良好的线性关系,检出限为5.0×10-9mol/L,对3.5×10-6mol/L的扑热息痛平行测定9次,其相对标准偏差为2.2%。该法用于片剂中扑热息痛含量的测定,结果满意。     

Quantum chemical study of the reaction mechanism of ozone and methane with fluorine and chlorine atoms

Ab initio calculations of the potential energy surface for the F + O₃ and Cl + O₃ reactions have been performed using the G3 and G3MP2 methods, which optimize the geometry configuration of reactants, products, intermediates, and transition states. The results show that fluorine atoms react with ozone as violently as chlorine atoms. At the same time, we have studied the reaction mechanisms of F atoms and Cl atoms with methane. It is found that fluorine atoms prefer to react with methane and chlorine atoms with ozone when there is competition between ozone and methane. Therefore, we can reasonably explain why chlorine atoms play the main role of reactants depleting ozone, while the more active fluorine atoms deplete less ozone. © 2002 Wiley Periodicals, Inc.; DOI 10.1002/qua.10119     

Arsenic-Rich Polyarsenides Stabilized by Cp*Fe Fragments

The redox chemistry of [Cp*Fe(η⁵-As₅)] ( 1 , Cp*=η⁵-C₅Me₅) has been investigated by cyclic voltammetry, revealing a redox behavior similar to that of its lighter congener [Cp*Fe(η⁵-P₅)]. However, the subsequent chemical reduction of 1 by KH led to the formation of a mixture of novel As_n scaffolds with n up to 18 that are stabilized only by [Cp*Fe] fragments. These include the arsenic-poor triple-decker complex [K(dme)₂][{Cp*Fe(μ,η^2:2-As₂)}₂] ( 2 ) and the arsenic-rich complexes [K(dme)₃]₂[(Cp*Fe)₂(μ,η^4:4-As₁₀)] ( 3 ), [K(dme)₂]₂[(Cp*Fe)₂(μ,η^2:2:2:2-As₁₄)] ( 4 ), and [K(dme)₃]₂[(Cp*Fe)₄(μ₄,η^{4:3:3:2:2:1:1}-As₁₈)] ( 5 ). Compound 4 and the polyarsenide complex 5 are the largest anionic As_n ligand complexes reported thus far. Complexes 2 – 5 were characterized by single-crystal X-ray diffraction, ¹H NMR spectroscopy, EPR spectroscopy ( 2 ), and mass spectrometry. Furthermore, DFT calculations showed that the intermediate [Cp*Fe(η⁵-As₅)]⁻, which is presumably formed first, undergoes fast dimerization to the dianion [(Cp*Fe)₂(μ,η^4:4-As₁₀)]²⁻.     

Ab initio study on the reaction mechanism of ozone with bromine atom

Ab initio calculations of the potential energy surface (PES) for the Br+O₃ reaction have been performed using the MP2, CCSD(T), and QCISD(T) methods with 6‐31G(d), 6‐311G(d), and 6‐311+G(3df). The reaction begins with a transition state (TS) when the Br atom attacks a terminal oxygen of ozone, producing an intermediate, the bromine trioxide (M), which immediately dissociates to BrO+O₂. The geometry optimizations of the reactants, products, and intermediate and transition states are carried out at the MP2/6‐31G(d) level. The reaction potential barrier is 3.09 kcal/mol at the CCSD(T)/6‐311+G(3df)//MP2 level, which shows that the bromine atom trends intensively to react with the ozone. The comparison of the Br+O₃ reaction with the F+O₃ and Cl+O₃ reactions indicates that the reactions of ozone with the halogen atoms have the similar reaction mechanism. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

Chemiluminescence of organometallic compounds in reactions with the free radical galvinoxyl

Chemiluminescence (CL) is observed in reactions of the free radical galvinoxyl (RO^•) with PhMgBr, PhMnCl, PhTi(BuⁱO)₃, and sodium naphthalenide or sodium anthracenide during their oxidation with air and in reactions of RO^• with the initial organometallic compounds. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 611–612, March, 1997.     

Chemiluminescence of Ru(bpy)3 2+* in the reaction of electron transfer from Ph3CNa to Ru(bpy)3 3+ in a solution

Conditions for the generation of the Ru(bpy)₃ ³⁺ complex in organic solvents (Me₃CN or MeNO₂) in the presence of small amounts of H₂SO₄ were found. Chemiluminescence was observed in the reaction of Ru(bpy)₃ ³⁺ with Ph₃Na in a THF-MeCN mixture. The chemiluminescence emitter was identified as Ru(bpy)₃ ^2+*. This emitter forms in the excited state in the elementary reaction of electron transfer from the Ph₃C⁻ anion to Ru(bpy)₃ ³⁺. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 292–294, February, 1999.     

Chemiluminecsence in the oxidation of Na2C60 by the (NH4)2Ce(NO3)6 complex in THF

Chemiluminescence (_max = 790 nm) in the oxidation of fulleride Na₂C₆₀ by the (NH₄)₂Ce(NO₃)₆ complex in THF was found. The ³C₆₀* triplet of fullerene formed in the transfer of an electron from the intermediate C₆₀ ^– anion to Ce^IV was suggested to be the chemiluminescence emitter.     

ToF‐SIMS studies of the oxidation of Fe by D2O vapour: comparison with XPS

The oxidation of iron (Fe) by water (D₂O) vapour at low pressures and room temperature was investigated using time‐of‐flight (ToF) SIMS. The results supported those found previously using XPS and the QUASES^? program in that a duplex oxide structure was found containing a thin outer surface hydroxide (Fe(OD)₂) layer over an inner oxide (FeO) layer. The extraordinary depth resolution of the ToF‐SIMS profiles assisted in identifying the two phases; this resolution was achieved by compensation for surface roughness. A substantial concentration of deuterium was found in the subsurface oxide layer. This observation confirmed previous assessments that the formation of FeO was from the reaction of Fe(OD)₂ with outward‐diffusing Fe, leaving deuterium as a reaction product. Copyright © 2005 John Wiley & Sons, Ltd.     

Density functional study of the insertion and ring-opening mechanism of MCP over Cp2LaH and Cp2LuH catalysts

The insertion and ring opening of methylenecyclopropane (MCP) catalyzed by Cp2LnH (Ln = La and Lu) was investigated using DFT method. Geometries and energies of the reactants, minima, and transition states for this reaction were obtained. The present study indicates the formation of Cp2LaH-MCP complex followed by 1,2-insertion through a tetrahedral transition state with subsequent ring opening at the proximal bond via hydrogen transfer transition state resulting in the formation of the final product.     

Quantum chemistry study on the mechanism of the reaction between ozone and 2,3,7,8‐TCDD

Despite of its fundamental importance, the mechanism of the reaction between ozone and dioxins are still lack detailed investigation so far. It is well-known that quantum chemical calculation is a well-established method for investigating chemical reactions. In this article, quantum chemical calculation was employed to investigate the mechanism of the reaction between ozone and dioxins, as exemplified by 2,3,7,8-TCDD. The theoretical study showed that, 2,3,7,8-TCDD was gradually destructed by ozone via six cleavages of the CC bonds. All the six cleavages of the CC bonds were calculated and discussed in detail based on the theoretical calculations by the UB3LYP/6-31G(d) method. At the same time, the energies of stationary points along the reaction process were calculated by the UMP2/6-311g(d,p)//UB3LYP/6-31G(d) method and the activation energy was obtained. The obtained activation energy was 12.25 kcal/mol, which was lower than that of the reaction between benzene and O₃(16.64 kcal/mol). This indicated that, by comparison with benzene, 2,3,7,8-TCDD could be more efficiently destructed by O₃. The reason for this result was also discussed. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Computational study on the reaction mechanism of atmospheric oxidation of ethanol with ozone

The reaction of C₂H₅OH and O₃ on the singlet potential energy surface is carried out using the MP2 and CCSD(T)//MP2 theoretical approaches in connection with the 6-311++G(d,p) basis set. Three pre-reactive complexes C1, C2, and C3 are formed between ethanol and ozone at atmospheric pressure and 298.15 K temperature. With variety of the complexes, seven types of product are obtained which four types of them have enough thermodynamic stability. In thermodynamic approach, the most favor product begins with the formation of pre-reactive C2 complex and produces the CH₃CH(OH)₂ + O₂ as final adduct in a process that is computed to be exothermic by ?53.759 kcal/mol and spontaneous reaction by ?51.833 kcal/mol in Gibbs free energy. In kinetic viewpoint, the formation of CH₃COH + cis-H₂O₃ as a final adducts is the most favor path.     

Luminescent probing of the Tb-C bond in a catalyst of diene polymerization based on ThCl3 · 3(BunO)3PO+Bui 3Al

The application of chemiluminescence and photoluminescence methods is shown to be promising for studying the mechanism of diene polymerization on Ziegler-Natta catalysts based on organolanthan ide and organoaluminum compounds.The authors are grateful to N. V. Duvakina and Yu. B. Monakov for polymerization of several samples.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 2011–2015, August, 1996.