UV and H2O2/UV degradation of a pharmaceutical intermediate in aqueous solution

The degradation of 5-methyl-1,3,4-thiadiazole-2-thiol (MMTD), a pharmaceutical intermediate found in some aquifers of Northern Italy, has been investigated by means of UV and UV/H2O2 treatments. The study has been carried out with a 17 W low pressure mercury lamp at room temperature, using a (100)/(1) (H2O2)/(MMTD) molar ratio. The results have demonstrated that: (i) with an initial MMTD concentration of 1 mg/l, 90% MMTD removal can be achieved within 1 hour or less than 5 minutes by UV or UV/H2O2 respectively; (ii) the sole UV irradiation does not cause any MMTD mineralization; (iii) with an initial MMTD concentration of 50 mg/l, 4 hours of UV/H2O2 treatment lead to an almost complete mineralization of the MMTD organic sulfur and to a partial mineralization of carbon (59%) and nitrogen (14%). The identification of degradation by-products, performed by HPLC-UV-MS analysis, revealed that the sole UV irradiation gives rise to the MMTD transformation into a single by-product that continuously accumulates in the solution. Conversely, the UV/H2O2 treatment forms seven intermediates that undergo further degradation through the breakdown of the thiadiazole ring. On the basis of the obtained results a degradation pathway has been proposed.     

UV/H2O2光助氧化降解丽华实军蓝制衣染料（英文）

本文对UV/H2O2光助氧化降解丽华实军蓝制衣染料的效果及其影响因素和动力学进行了研究。结果表明,UV/H2O2对丽华实军蓝染料废液具有很好的处理效果,用量少,处理浓度高,且在发生光助氧化降解的同时还伴随着光分解反应。UV/H2O2体系的光助氧化反应和UV体系的光分解反应均为表观一级反应,前者活化能9.71 kJ.mol-1,指前因子1.61 min-1,后者活化能50.3 kJ.mol-1,指前因子3.88×105min-1。染料溶液初始pH为强碱性(pH=12)时染料降解率最大。     

Kinetic modeling of aqueous phenol degradation by UV/H2O2 process

A dynamic kinetic model for the oxidation of phenol in water by an UV/H₂O₂ process is developed. The model is based on the elementary chemical and photochemical reactions, initiated by the photolysis of hydrogen peroxide into hydroxyl radicals. The model is validated by using experimental data obtained from the open literature for an actual UV/H₂O₂ process. Using those data and the developed kinetic model, kinetic rate constants for phenol intermediates, catechol and hydroquinone, are estimated. Moreover, the optimum initial hydrogen peroxide concentration is estimated by means of the validated model. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 40: 34–43, 2008     

Comparative Effect of UV,UV/H2O2 and UV/H2O2/Fe on Terbuthylazine Degradation in Natural and Ultrapure Water

Different advanced oxidation processes (AOPs) (ultraviolet radiation, hydrogen peroxide photolysis and photo-Fenton) were applied to test the degradation of terbuthylazine in three types of water: (a) ultrapure water, (b) surface water from the Gaditana area (Los Hurones reservoir, Cádiz, Spain) and (c) groundwater from the Tempul spring in Jerez de la Frontera (Cádiz, Spain). The experiments were carried out on a laboratory scale, using two different types of reactors, batch and semi-continuous. In batch reactors, the most efficient process for the experiments carried out with both ultrapure water and underground groundwater was ultraviolet radiation, whereas for surface water from the Gaditana area, the process that obtained the best results was the photolysis of hydrogen peroxide with 2.5 mg L⁻¹ of H₂O₂. In semi-continuous reactors, the most efficient process was the photolysis of hydrogen peroxide with 2.5 mg L⁻¹ of H₂O₂ for all the matrices studied. In both types of reactors, terbuthylazine degradation percentages higher than 90% were achieved; the main difference was in the reaction time, which varied from minutes in the batch reactor to seconds in the semi-continuous reactor. In all the applied AOPs, N-terbutyl-6-hydroxy-N′ethyl-1,3,5-triazine-2,4-diamine (TBA-212) was generated as a reaction intermediate.     

Ce(H2O)(PO4)3/2(H3O)1/2(H2O)1/2, a second entry in the structural chemistry of cerium(IV) phosphates

A cerium(IV) phosphate has been prepared using precipitation methods and its structure has been solved by single crystal X-ray diffraction (R₁ = 0.0292 for 3092 reflections with I>2σ(I) and wR₂ = 0.0540). Ce(H₂O)(PO₄)_3/2(H₃O)_1/2(H₂O)_1/2 crystallises in the monoclinic space group C2/c (a = 15.7058(17) Å, b = 9.6261(9) Å, c = 10.1632(4) Å, ß = 121.623(7)°, and V = 1308.4 (2) Å³). Its structure is based on a negatively charged 3D framework, made of cerium atoms connected by PO₄ tetrahedra. There are two types of PO₄ units; one shares only corners with the cerium coordination polyhedra while the other one shares edges and corners. This structure also includes hydronium cations, to balance the framework charge, and water molecules. One special feature of this 3D framework is the formation of interconnected tunnels which extend along the c axis and contain the hydronium cations and the water molecules. This open framework and the presence of cationic species in the tunnels are in perfect agreement with the previously reported ion exchange properties.     

脂肪酸铕配合物/PMMA的合成及发光性能

以一定比例正辛酸和月桂酸为第一配体,通过皂化法合成了脂肪酸铕配合物,并溶于甲基丙烯酸甲酯(MMA)单体通过本体聚合得到了含脂肪酸铕的PMMA光致发光聚合物材料AxByEu/PMMA(A为正辛酸根,B为月桂酸根,x、y分别表示正辛酸和月桂酸的摩尔比). 考察了不同的第二配体(咔唑、二甲基-联吡啶、邻菲罗啉、噻吩甲酰三氟丙酮HTTA)对脂肪酸铕聚合物发光性能的影响,选择出合适的第二配体HTTA,合成了A3Eu/HTTA/PMMA聚合物. 通过红外光谱、紫外光谱及荧光光谱测试技术对配合物及聚合物的结构和荧光性能进行表征. 结果表明,合成的含脂肪酸铕配合物及其聚合物均具有很好的光致发光性能,紫外激发能发射Eu3+离子的特征红光. 当HTTA的质量分数减小至MMA的0.02%时,仍能很好地促进体系的发光,且不影响聚合物本身的透明性.     

DNA degradation and oxidation of o-phenylenediamine. Metal ions and H2O2, 8

In earlier papers it has been stated, that the catalytic activity of several metal complexes in H₂O₂ decomposition is caused by the formation of ternary HOO^?-Me²⁺-ligand complexes. The present investigation deals with the effect of traces of metal ions on two other reactions. The degradation of DNA by autoxidizable, H₂O₂ producing methylhydrazines is stopped by P₂O₇^4?. This effect is shown to be due to complex formation of the metal ions with P₂O₇^?4, preventing the formation of the catalytically active ternary complex. The catalysis of the H₂O₂ oxidation of o-phenylenediamine by pyridine-2,6-dicarboxylic acid is dependent on traces of Fe²⁺ ions; this latter effect is equally suppressed by P₂O₇^?4.     

Diffusivity fractionations of H2(16)O/H2(17)O and H2(16)O/H2(18)O in air and their implications for isotope hydrology

We have determined the isotope effects of (17)O and (18)O substitution of (16)O in H(2)O on molecular diffusivities of water vapor in air by the use of evaporation experiments. The derived diffusion fractionation coefficients (17)alpha(diff) and (18)alpha(diff) are 1.0146 +/- 0.0002 and 1.0283 +/- 0.0003, respectively. We also determined, for the first time, the ratio ln((17)alpha(diff))/ln((18)alpha(diff)) as 0.5185 +/- 0.0002. This ratio, which is in excellent agreement with the theoretical value of 0.5184, is significantly smaller than the ratio in vapor-liquid equilibrium (0.529). We show how this new experimental information gives rise to (17)O excess in meteoric water, and how it can be applied in isotope hydrology.     

脂肪酸铕配合物聚合物材料的合成及发光性质

以一定比例正辛酸和月桂酸为第一配体,通过皂化法合成了脂肪酸铕配合物,并溶于甲基丙烯酸甲酯（MMA）单体通过本体聚合得到了含脂肪酸铕的PMMA光致发光聚合物材料AxByEu/PMMA（其中A=正辛酸根,B=月桂酸根,x、y分别表示正辛酸和月桂酸的比例）。考察了不同的第二配体（咔唑、二甲基-联吡啶、邻菲罗啉、噻吩甲酰三氟丙酮HTTA）对脂肪酸铕聚合物发光性能的影响,选择出合适的第二配体HTTA,进而合成了A3Eu/HTTA/PMMA聚合物。通过红外光谱、紫外光谱及荧光光谱对脂肪酸铕配合物及聚合物的结构和荧光性能进行表征。结果表明：合成的脂肪酸铕配合物及其聚合物均具有很好的光致发光性能,紫外激发能发射Eu3+离子的特征红光。当HTTA的质量分数减小至0.02%时,仍能很好地促进体系的发光,且不影响聚合物本身的透明性。     

Hydrogen peroxide oxidation of mustard-model sulfides catalyzed by iron and manganese tetraarylporphyrines. Oxygen transfer to sulfides versus H(2)O(2) dismutation and catalyst breakdown.

Fe(III)- and Mn(III)-meso-tetraarylporphyrin catalysis of H(2)O(2) oxidation of dibenzyl and phenyl-2-chloroethyl sulfides, 1, is investigated in ethanol with the aim of designing catalytic systems for mustard decontamination. The sulfide conversion, the sulfoxide and sulfone yields, the oxygen transfer from H(2)O(2) to the sulfide, and the catalyst stability depend markedly on the metal, on the substituents of its ligand, and on the presence or the absence of a cocatalyst, imidazole or ammonium acetate. With Fe, sulfones, the only oxidation products, are readily obtained whatever the ligand (TPP, F(20)TPP, or TDCPP) and the cocatalyst; the oxygen transfer is fairly good, up to 95% when the catalyst concentration is small ([1]/[Cat] = 420); the catalyst breakdown is insignificant only in the absence of any cocatalyst. With Mn, the sulfide conversion is achieved completely when the ligand is TDCPP or TSO(3)PP, but not F(20)TPP or TPP; a mixture of sulfoxide, 2, and sulfone, 3, is always obtained with [2]/[3] = 3.5-0.85 depending on the ligand and the cocatalyst (electron withdrawing substituents favor 3 and NH(4)OAc, 2). The catalyst stability is very good, but the oxygen transfer is poor whatever the ligand and the cocatalyst. These results are discussed in terms of a scheme in which sulfide oxygenation, H(2)O(2) dismutation, and oxidative ligand breaking compete. It is shown that the efficiency of the oxygen transfer is related not only to the rate constant of the dismutation route but also to the concentration of the active metal-oxo intermediate, most likely a perferryl or permanganyl species, i.e., to the rate of its formation.     

Dielectric characteristics of O2(H2O)i and (O2)2(H2O)i clusters. Computer-aided experiment

Absorption of oxygen molecules by water clusters with sizes of 10 ≤ i ≤ 50 is studied by the molecular dynamics method using the modified TIP4P model. It is revealed that the total dipole moment of the clusters nonmonotonically increases with their sizes. Absorption of O₂ molecules tends to raise the static permittivity of the ultradispersed medium formed by the clusters. The real and imaginary parts of the permittivity of water clusters with absorbed O₂ molecules are aperiodic functions of frequency. The permittivity components turn out to be nonmonotonic functions of cluster sizes. The IR absorption and reflectance spectra are calculated for clusters of pure water and aggregates with absorbed O₂ molecules. After the addition of oxygen molecules, the absorption coefficient of the clusters decreases, while the reflection coefficient increases. It is concluded that the capture of oxygen molecules by atmospheric moisture may reduce the greenhouse effect. Original Russian Text ? A.E. Galashev, V.N. Chukanov, O.A. Galasheva, 2006, published in Kolloidnyi Zhurnal, 2006, Vol. 68, No. 2, pp. 155–160.     

Kinetics and products of chlorine atom initiated oxidation of HCF2OCF2OCF2CF2OCF2H and HCF2O(CF2O)n‐(CF2CF2O)mCF2H

Smog chamber/FTIR techniques were used to measure k(Cl + HCF₂OCF₂OCF₂‐CF₂OCF₂H) = k(Cl + HCF₂O(CF₂O)_n(CF₂CF₂O)_mCF₂H) = (5.0 ± 1.4) × 10^?17 cm³ molecule^?1 s^?1 in 700 Torr of N₂/O₂ diluent at 296 ± 1 K. The Cl‐initiated atmospheric oxidation of HCF₂OCF₂OCF₂CF₂OCF₂H and the sample of HCF₂O(CF₂O)_n(CF₂CF₂O)_mCF₂H used in this work gave COF₂ in molar yields of (476 ± 36)% and (859 ± 63)%, respectively, with no other observable carbon containing products (i.e., essentially complete conversion of both hydrofluoropolyethers into COF₂). The results are discussed with respect to the atmospheric chemistry and environmental impact of hydrofluoropolyethers of the general formula HCF₂O(CF₂O)_n(CF₂CF₂O)_mCF₂H. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: 819–825, 2008     

Triple hydroxylation of tetracenomycin A2 to tetracenomycin C involving two molecules of O(2) and one molecule of H(2)O

The TcmG or ElmG oxygenase-catalyzed triple hydroxylation of tetracenomycin (Tcm) A2 to Tcm C proceeds via a novel monooxygenase-dioxygenase mechanism, deriving the 4- and 12a-OH groups of Tcm C from two molecules of O(2) and the 4a-OH group of Tcm C from a molecule of H(2)O. These results suggest a mechanistic analogy among TcmG, ElmG, and the bacterial and fungal hydroquinone epoxidizing dioxygenases, as well as the mammalian vitamin K-dependent gamma-glutamyl carboxylase.     

Solvent-free oxidation of organic compounds with Fe(NO3)3.9H2O catalyzed by NaHSO4.H2O

The oxidation of alcohols, methoxymethyl ethers, acetals and ketals to their corresponding carbonyl compounds with Fe(NO₃)₃.9H₂O is efficiently promoted in the presence of NaHSO₄.H₂O. All reactions were performed in the absence of solvent in good to high yields. Availability, stability and non-toxicity of the reagents, mild reaction conditions, absence of solvent, relatively short reaction times, good to high yields of the products, and easy work-up are advantages of the proposed method.     

Dissociation and IVR pathways for the CF3H(H2O)3 cluster

Classical trajectory simulations are used to study the intramolecular dynamics of isolated CF₃H and the CF₃H(H₂O)₃ cluster, by either exciting the CH stretch local mode to then=6 level or by adding an equivalent amount of energy to an OH stretch normal mode. Energy transfer from the CH local mode is statistically the same for CF₃H(H₂O)₃ as for isolated CF₃H, and agrees with previous experimental studies. Clusters excited with 6 quanta in the CH local mode are remarkably stable. Though the CF₃H-(H₂O)₃ intermolecular potential is only 1.5 kcal/mol, only 1 of 26 clusters excited with 6 quanta in the CH local mode dissociate within 10 ps. The absorption linewidth for the CH local mode in CF₃H(H₂O)₃ is related to IVR within CF₃H and not to the unimolecular lifetime of the cluster. When an OH stretch normal mode of the cluster is excited, energy transfer to CF₃H is negligible and nearly one half of the clusters dissociate within 10 ps.     

Activation and transfer of oxygen—IX : Nonenzymic hydroxylation of phenylalanine by model systems of dihydroalloxazine/O2 dihydroalloxazine/H2O2 and alloxazinium cation/H2O

Efficient hydroxylations were effected without addition of metal compounds. In the dihydroalloxazine system HO· radicals were the hydroxylating species according to the stoichiometry and the distribution of the hydroxyphenylalanine isomers. The OH radicals were generated in one-electron reductions of A^R-OOH or H₂O₂, in which a dihydroalloxazine or a semiquinone acted as the reducing agent. The yield of hydroxylation varied in dependence on the further oxidation of the hydroxycyclohexadienyl radicals. Quantitative disproportionation occurred in 6N H₂SO₄, while an attack by O₂, H₂O₂ or A^R-OOH predominated in the pH region 0–7. The influence of a HO- consuming aliphatic compound e.g. EDTA was studied.Hydroxylating species are also formed in the attack of an alloxazinium cation by H₂O₂, depending on the acidity of the medium.     

Efficient hydroxylation of aromatic compounds catalyzed by an iron(II) complex with H2O2

A mononuclear iron(II) complex, Et₄N[Fe(C₁₀H₆NO₂)₃], coordinated by three 1‐nitroso‐2‐naphtholate ligands in a fac‐N₃O₃ geometry, was initiated to catalyze the direct hydroxylation of aromatic compounds to phenols in the presence of H₂O₂ under mild conditions. Various reaction parameters, including the catalyst dosage, temperature, mole ratio of H₂O₂ to benzene, reaction time and solvents which could affect the hydroxylation activity of the catalyst, were investigated systematically for benzene hydroxylation to obtain ideal benzene conversion and high phenol distribution. Under the optimum conditions, the benzene conversion was 10.2% and only phenol was detected. The catalyst was also found to be active towards hydroxylation of other aromatic compounds with high substrate conversions. The hydroxyl radical formed due to the reaction of the catalyst and H₂O₂ was determined to be the crucial active intermediate in the hydroxylation. A rational pathway for the formation of the hydroxyl radical was proposed and justified by the density functional theory calculations. Copyright © 2014 John Wiley & Sons, Ltd.     

Two Heteroleptic Zinc(II) Complexes: [Zn(phen)(C9H15O6)2] and [Zn2(phen)2(H2O)2(C10H16O4)2] · 3H2O

Reactions of a freshly prepared Zn(OH)_2‐2x(CO₃)x · yH₂O precipitate, phenanthroline with azelaic and sebacic acid in CH₃OH/H₂O afforded [Zn(phen)(C₉H₁₅O₄)₂] ( 1 ) and [Zn₂(phen)₂(H₂O)₂(C₁₀H₁₆O₄)₂] · 3H₂O ( 2 ), respectively. They were structurally characterized by X‐ray diffraction methods. Compound 1 consists of complex molecules [Zn(phen)(C₉H₁₅O₄)₂] in which the Zn atoms are tetrahedrally coordinated by two N atoms of one phen ligand and two O atoms of different monodentate hydrogen azelaato groups. Intermolecular C(alkyl)‐H···π interactions and the intermolecular C(aryl)‐H···O and O‐H···O hydrogen bonds are responsible for the supramolecular assembly of the [Zn(phen)(C₉H₁₅O₄)₂] complexes. Compound 2 is built up from crystal H₂O molecules and the centrosymmetric binuclear [Zn₂(phen)₂(H₂O)₂(C₁₀H₁₆O₄)₂] complex, in which two [Zn(phen)(H₂O)]²⁺ moieties are bridged by two sebacato ligands. Through the intermolecular C(alkyl)‐H···O hydrogen bonds and π‐π stacking interactions, the binuclear complex molecules are assembled into layers, between which the lattice H₂O molecules are sandwiched. Crystal data: ( 1 ) C2/c (no. 15), a = 13.887(2), b = 9.790(2), c = 22.887(3)Å, β = 107.05(1)°, U = 2974.8(8)ų, Z = 4; ( 2 ) P1¯ (no. 2), a = 8.414(1), b = 10.679(1), c = 14.076(2)Å, α = 106.52(1)°, β = 91.56(1)°, γ = 99.09(1)°, U = 1193.9(2)ų, Z = 1.