用离子色谱法测定水中的二氧化氯、氯、亚氯酸根及氯酸根

建立了一种测定水中的ClO2、Cl2、ClO2^-、ClO3^-离子色谱法,在含有碳酸氢钠缓冲溶液的中性条件下,用NaNO2将ClO2、Cl2还原为ClO2^-、Cl^-,通过测定ClO^-和NO3^-的变化值,间接测定ClO2和Cl2。加入硫代乙酰胺(TAA)作掩蔽剂测定ClO2^-。     

Application of an amperometric sensor to in-line monitoring of pulp bleaching with chlorine dioxide

Chlorine dioxide is replacing chlorine as the active compound in pulp bleaching in order to reduce the amount of chlorine used in the process and hence also in the waste waters. In bleaching with chlorine dioxide part of the effective bleaching chemical is usually chlorite. The electrochemistry of chlorine dioxide and chlorite at solid electrodes was studied by cyclic voltammetry at different pH values. The observed voltammograms indicated that reduction of chlorine dioxide gives chlorite and oxidation of chlorite gives chlorine dioxide. Both voltammograms were well developed, indicating a reversible process. Both platinum and glassy carbon were used as the working electrode. The dependence of the limiting current of chlorine dioxide and chlorite on pH was studied at both electrodes. The method was tested in the chlorine dioxide bleaching stage D1 in a typical bleaching process. A good correlation was found between the concentrations of chlorine dioxide and chlorite measured by the in-line amperometric method and a standard titrimetric method.     

Potentiometric titration of chlorine and its oxy compounds in water

Potentiometric titrations at constant current with identical platinum electrodes are applied to mixtures of chlorine, chlorine dioxide and chlorite. The procedure is compared with the common amperometric method. Chlorine can be titrated with phenylarsine oxide at pH 7 even in mixtures with chlorine dioxide and chlorite, and three-component mixtures can be resolved by titrations at pH 2 and 7 with and without iodide addition. The behavior of chlorine and chlorite mixtures can be characterized by appropriate titrations.     

Equatorial Perturbation Driven Reaction Bifurcation in Non-Heme Iron Complexes for Chlorite Oxidation

Chlorine oxyanions have various applications, such as bleaching and oxidizers in rocket fuels. However, their high solubility in water and long environmental lifetimes have led to ecological concerns, especially regarding drinking water quality. This study focuses on the conversion of chlorite to chlorine dioxide, which is of significant interest as it exhibits superior antimicrobial activity and generates less harmful byproducts for water treatment. Two nonheme iron(II) complexes capable of producing chlorine dioxide from chlorite at room temperature and pH 5.0 are presented. These complexes oxidize chlorite through high-valent iron (IV)-oxo intermediates formed in-situ. The study establishes second-order rate constants for chlorite oxidation and investigates the effects and mechanisms involved by substituting a methyl group in the secondary coordination sphere of the Fe^IV(O)(N4Py) system. By employing kinetic analysis and spectroscopic investigations, the crucial elements for the reaction mechanism in chlorite oxidation are identified. These findings pave the way for future advancements in this field.     

Untersuchungen an Stickstoff-Chlor-Verbindungen. VII. Neue N-Perchlorylverbindungen durch Ammono- und Aminolyse von Dichlorheptoxid

Studies on Nitrogen Chlorine Compounds. VII. New N-Perchloryl Compounds by Ammono- and Aminolysis of Dichlorine Heptoxide The reaction of dichlorine heptoxide with ammonia, primary and secondary amines leads to compounds belonging to the class of amides of perchloric acid. The remaining acidic hydrogen atoms on nitrogen could be replaced by metal cations. The compounds were characterized as far as possible by analysis, IR and ¹H-NMR spectroscopy. The changing of the bond character between nitrogen and chlorine depending on the substituents on nitrogen is discussed.     

Zur Dismutierung von C1-Fluorchlorkohlenwasserstoffen an Metalloxid- und Halogenidoberflächen

Dismutation of C₁ – Fluorine Chlorine Hydro Carbons at Surfaces of Metal Oxides and halides Dismutation of C₁-fluorine chlorine hydro carbons has been investigated at surfaces of aluminium and chromium chlorides respectively fluorides. Dismutation reactions have been observed only after halogen exchange at such surfaces of solids which contain both, chloride and fluoride. A mechanism of dismutation is suggested which underlies a concerted chlorine/fluorine and fluorine/chlorine exchange between the solid and the gas phase. The results are discussed in connection with thermodynamically considerations.     

Dissection of the mechanism of manganese porphyrin-catalyzed chlorine dioxide generation

Chlorine dioxide, an industrially important biocide and bleach, is produced rapidly and efficiently from chlorite ion in the presence of water-soluble, manganese porphyrins and porphyrazines at neutral pH under mild conditions. The electron-deficient manganese(III) tetra-(N,N-dimethyl)imidazolium porphyrin (MnTDMImP), tetra-(N,N-dimethyl)benzimidazolium (MnTDMBImP) porphyrin, and manganese(III) tetra-N-methyl-2,3-pyridinoporphyrazine (MnTM23PyPz) were found to be the most efficient catalysts for this process. The more typical manganese tetra-4-N-methylpyridiumporphyrin (Mn-4-TMPyP) was much less effective. Rates for the best catalysts were in the range of 0.24-32 TO/s with MnTM23PyPz being the fastest. The kinetics of reactions of the various ClO(x) species (e.g., chlorite ion, hypochlorous acid, and chlorine dioxide) with authentic oxomanganese(IV) and dioxomanganese(V)MnTDMImP intermediates were studied by stopped-flow spectroscopy. Rate-limiting oxidation of the manganese(III) catalyst by chlorite ion via oxygen atom transfer is proposed to afford a trans-dioxomanganese(V) intermediate. Both trans-dioxomanganese(V)TDMImP and oxoaqua-manganese(IV)TDMImP oxidize chlorite ion by 1-electron, generating the product chlorine dioxide with bimolecular rate constants of 6.30 × 10(3) M(-1) s(-1) and 3.13 × 10(3) M(-1) s(-1), respectively, at pH 6.8. Chlorine dioxide was able to oxidize manganese(III)TDMImP to oxomanganese(IV) at a similar rate, establishing a redox steady-state equilibrium under turnover conditions. Hypochlorous acid (HOCl) produced during turnover was found to rapidly and reversibly react with manganese(III)TDMImP to give dioxoMn(V)TDMImP and chloride ion. The measured equilibrium constant for this reaction (K(eq) = 2.2 at pH 5.1) afforded a value for the oxoMn(V)/Mn(III) redox couple under catalytic conditions (E' = 1.35 V vs NHE). In subsequent processes, chlorine dioxide reacts with both oxomanganese(V) and oxomanganese(IV)TDMImP to afford chlorate ion. Kinetic simulations of the proposed mechanism using experimentally measured rate constants were in agreement with observed chlorine dioxide growth and decay curves, measured chlorate yields, and the oxoMn(IV)/Mn(III) redox potential (1.03 V vs NHE). This acid-free catalysis could form the basis for a new process to make ClO(2).     

Kernresonanz-spektroskopische Untersuchung protonierter Stickstoffverbindungen in Trifluoressigsäure

The nuclear magnetic resonance spectra of a series of protonated organic nitrogen compounds in trifluoroacetic acid solution have been studied. A direct correlation between the exchange rate of the ammonium protons and the acidity constant of the functional group is established. Substituted anilinium and pyridinium ions with pK values below 4 show coalescence for the signals of N^⊕? H protons and disappearence of the coupling with the α protons.     

Saturated 5-membered ring conformations. 2—1H NMR study of protonated N-methylpyrrolidines

The ¹H NMR spectra of the protonated and unprotonated forms of cis- and trans-N-methylhexahydroisoindoline, of 1,3,3,4,4-pentamethylpyrrolidine and of 1,3,3-trimethylpyrrolidine were analyzed. The coupling constants between the NH⊕ and the CH protons α to the nitrogen allowed the study of the conformation of the cyclic systems in pseudorotation.     

Chemische Reaktionen in Salzschmelzen. XX. Zur elektrochemischen Wiedergewinnung von Chlor aus Chlorwasserstoff

Chemical Reactions in Molten Salts. XX. Electrochemical Recycling of Chlorine from Hydrogenchloride A continuously working process for splitting up waste hydrogenchloride yielding chlorine and hydrogen is described. Hydrogenchloride is reduced by reactive metals or low-valent metal ions in a molten salt bath forming hydrogen. The resulting metal chloride dissolves in the melt and is electrolized to chlorine and the previous metal. Among the investigated systems most appropriate are Cd/CdCl₂? NaCl, Zn/ZnCl₂? KCl and Al/NaAlCl₄, respectively, which proceed with suspensions of a solid metal or utilizing the solubility of the metal. – The use of a diaphragm permits to construct the cathode chamber as a bubble column or agitator vessel. The process is comparable with the electrolysis of hydrochloric acid with respect to energy consumption, purity of products and volume-time-yields (RZA).     

电子活度和pH对二氧化氯制备和稳定性的影响

建立了氯体系电子活度（pε）和pH优势区域图（pε-pH）图,从酸化、氧化和还原的角度,探讨了标准状态下pε和pH对二氧化氯制备和稳定性的影响。实际生产不可能制备绝对纯净的二氧化氯。对于不同的水体,由于其pε和pH值不同,因而可能使二氧化氯表现出不同的稳定性特征。如果水溶液中二氧化氯不歧化为氯酸根,二氧化氯相对稳定,并与亚氯酸根、氯分子或氯离子稳定共存。当氯体系实现最终平衡时,二氧化氯仅在强酸介质中优势存在,随着酸度降低,二氧化氯歧化为氯酸根和氯气,水溶性和二氧化氯在常规pH条件下不稳定。     

Oxyhalogen-sulfur chemistry: kinetics and mechanism of oxidation of N-acetylthiourea by chlorite and chlorine dioxide

The oxidation reactions of N-acetylthiourea (ACTU) by chlorite and chlorine dioxide were studied in slightly acidic media. The ACTU-ClO(2)(-) reaction has a complex dependence on acid with acid catalysis in pH > 2 followed by acid retardation in higher acid conditions. In excess chlorite conditions the reaction is characterized by a very short induction period followed by a sudden and rapid formation of chlorine dioxide and sulfate. In some ratios of oxidant to reductant mixtures, oligo-oscillatory formation of chlorine dioxide is observed. The stoichiometry of the reaction is 2:1, with a complete desulfurization of the ACTU thiocarbamide to produce the corresponding urea product: 2ClO(2)(-) + CH(3)CONH(NH(2))C=S + H(2)O --> CH(3)CONH(NH(2))C=O + SO(4)(2-) + 2Cl(-) + 2H(+) (A). The reaction of chlorine dioxide and ACTU is extremely rapid and autocatalytic. The stoichiometry of this reaction is 8ClO(2)(aq) + 5CH(3)CONH(NH(2))C=S + 9H(2)O --> 5CH(3)CONH(NH(2))C=O + 5SO(4)(2-) + 8Cl(-) + 18H(+) (B). The ACTU-ClO(2)(-) reaction shows a much stronger HOCl autocatalysis than that which has been observed with other oxychlorine-thiocarbamide reactions. The reaction of chlorine dioxide with ACTU involves the initial formation of an adduct which hydrolyses to eliminate an unstable oxychlorine intermediate HClO(2)(-) which then combines with another ClO(2) molecule to produce and accumulate ClO(2)(-). The oxidation of ACTU involves the successive oxidation of the sulfur center through the sulfenic and sulfinic acids. Oxidation of the sulfinic acid by chlorine dioxide proceeds directly to sulfate bypassing the sulfonic acid. Sulfonic acids are inert to further oxidation and are only oxidized to sulfate via an initial hydrolysis reaction to yield bisulfite, which is then rapidly oxidized. Chlorine dioxide production after the induction period is due to the reaction of the intermediate HOCl species with ClO(2)(-). Oligo-oscillatory behavior arises from the fact that reactions that form ClO(2) are comparable in magnitude to those that consume ClO(2), and hence the assertion of each set of reactions is based on availability of reagents that fuel them. A computer simulation study involving 30 elementary and composite reactions gave a good fit to the induction period observed in the formation of chlorine dioxide and in the autocatalytic consumption of ACTU in its oxidation by ClO(2).     

Direct potentiometric titration of chlorite in presence of chlorate, chlorine dioxide and chloride

A direct potentiometric titration of chlorite in the presence of chlorate, chlorine dioxide and chloride is described. Chlorite is determined in 0.01-0.0005 M sodium chlorite at pH 2.0-3.5 using hypochlorite solution. The course of the reaction is followed potentiometrically using saturated calomel and platinum electrodes; the end-point is indicated by a potential jump of about 230 mV. Under these conditions no reaction takes place with chlorate, chlorine dioxide or chloride. Previously, the determination of chlorite in such mixtures was only possible by difference from several oxidimetric titrations.     

激光引发的氯自由基与1，2-二氯乙烷的反应研究

1,2-二氯乙烷裂解反应是一个自由基链反应。在热反应中,为了克服引发自由基反应所需要的能量,反应必须在较高温度下进行。但是在光化学反应中,特别是应用了激光引发自由基,使得这一裂解反应可以在较低的温度下进行。因此利用激光引发的自由基链反应,不仅在理论上有浓厚的兴趣,并且在工业上有广阔的应用前景。Wolfrum曾详细地研究过利用准分子激光(KrF激光)裂解1,2-二氯乙烷的反应。由于1,2-二氯乙烷对KrF激光有较强的吸收,容易产生氯自由基,使整个链反应速率决定步骤由链的引发变为链的传递,而降低反应温度。因为光化学反应温度低,抑止了很多副反应,从而提高反应的选择性。     

Aktivierung von Kohlendioxid durch Metall(0)-Komplexe. Oxidative Kopplung von Kohlendioxid und Aldehyden am Zentralatom Nickel(0)

Activation of Carbon Dioxide by Metal(0) Complexes. Oxidative Coupling of Carbon Dioxide and Aldehydes on the Central Atom Nickel(0) The oxidative coupling of carbon dioxide and aliphatic aldehydes on the complex moiety 2,2′-Bipyridine-nickel(0) yields crystalline complexes, containing five-membered chelate rings with Nickel-C- and Nickel-O-σ-bonds (Nickela-2,4-dioxolane-3-one). IR, UV/VIS- and H-NMR-spectra are reported; the mechanism of the coupling reaction is discussed.     

S-oxygenation of thiocarbamides II: Oxidation of trimethylthiourea by chlorite and chlorine dioxide

The kinetics of the oxidation of a substituted thiourea, trimethylthiourea (TMTU), by chlorite have been studied in slightly acidic media. The reaction is much faster than the comparable oxidation of the unsubstituted thiourea by chlorite. The stoichiometry of the reaction was experimentally deduced to be 2ClO2- + Me2N(NHMe)C=S + H2O --> 2Cl- + Me2N(NHMe)C=O + SO4(2-) + 2H+. In excess chlorite conditions, chlorine dioxide is formed after a short induction period. The oxidation of TMTU occurs in two phases. It starts initially with S-oxygenation of the sulfur center to yield the sulfinic acid, which then reacts in the second phase predominantly through an initial hydrolysis to produce trimethylurea and the sulfoxylate anion. The sulfoxylate anion is a highly reducing species which is rapidly oxidized to sulfate. The sulfinic and sulfonic acids of TMTU exists in the form of zwitterionic species that are stable in acidic environments and rapidly decompose in basic environments. The rate of oxidation of the sulfonic acid is determined by its rate of hydrolysis, which is inhibited by acid. The direct reaction of chlorine dioxide and TMTU is autocatalytic and also inhibited by acid. It commences with the initial formation of an adduct of the radical chlorine dioxide species with the electron-rich sulfur center of the thiocarbamide followed by reaction of the adduct with another chlorine dioxide molecule and subsequent hydrolysis to yield chlorite and a sulfenic acid. The bimolecular rate constant for the reaction of chlorine dioxide and TMTU was experimentally determined as 16 +/- 3.0 M(-1) s(-1) at pH 1.00.     

Computational investigation of the concerted dismutation of chlorite ion by water-soluble iron porphyrins

A detailed density functional theory examination of the reaction of an iron porphyrin chlorite dismutase model complex with chlorite was performed. We find that the molecular oxygen production observed occurs via the formation of η(1)-Fe(III) chlorite species, followed by the formation of O═Fe(IV) (compound II) and chlorine monoxide through homolytic bond cleavage. Chlorine monoxide then rebounds to form Fe(III)-peroxyhypochlorite followed by subsequent loss of chloride and loss of dioxygen accompanied by spin conversion to produce the Fe(III) complex and complete the catalytic cycle.     

Schwefeldioxid als Ligand und Synthon. IX. Reaktionen von Cobaltcarbonylen mit Schwefeldioxid – Synthese und Charakterisierung von Alkoxysulfinyl-Cobaltcarbonyl-Komplexen

Sulfur Dioxide as Ligand and Synthon. IX. Reactions of Cobalt Carbonyls with Sulfur Dioxide – Synthesis and Characterization of Alkoxysulfinyl-Cobalt Carbonyl Complexes Reactions of phosphine substituted Co₂(CO)₈, (Ph₂P–(CH₂)_n–PPh₂: n = 1, dppm; n = 2, dppe; n = 3, dppp; n = 4, dppb), alkylcobalt carbonyls and alkoxycobalt carbonyls with sulfur dioxide have been investigated. The SO₂ containing cobalt complexes are characterized by means of I.R., ¹H-NMR, and mass spectra. Further on synthesis and properties of new alkoxysulfinylphosphine-cobalttricarbonyl complexes of the type ROS(O)Co(CO)₃PR₃¹ (R = Ph₃Si, Me; R¹ = Et, i-Pr, Ph) are described.     

Synthese von 4-Trichlorsilylmethylbenzonitril und 4-(2-Trichlorsilyläthyl)pyridin zur Oberflächenmodifikation von Zinndioxid

Synthesis of 4-Trichlorosilylmethylbenzonitrile and 4-(2-Trichlorosilylethyl)pyridine for Surface Modification of Tin Dioxide We describe the synthesis of 4-(trichlorosilylmethyl)benzonitrile and 4-(2-trichlorosilylethyl)pyridine, starting from 4-(bromomethyl)benzonitrile and trichlorosilane or vinylpyridine and trichlorosilane. Trimethoxysilanes are obtained by reaction of the trichlorosilyl compounds with methyl orthoformate. 4-(Trichlorosilylmethyl)benzonitrile and 4-(2-trichlorosilylethyl)pyridine are used to modify the surface of tin dioxide.     

Zur Bestimmung von Chlordioxid neben wirksamem Chlor und Natriumchlorit im Trinkwasser

Zusammenfassung Es wird ein häufig angewendetes Verfahren zur Bestimmung von Chlor, Chlordioxid und Chlorit in Wasser überprüft und kritisch besprochen. Eine neue Bestimmungsmethode wird beschrieben. Sie vermeidet die bisherigen Fehlerquellen durch Kombination einer colorimetrischen Chlorbestimmung nach Asmus u. Garschagen ¹ (1953) mit zwei potentiometrischen Titrationen. Mit Hilfe dieses Verfahrens werden Chlor, Chlordioxid und Chlorit in Wasser im Bereich von 0,03–2 mg/l Gesamtaktivchlor nebeneinander bestimmt. Weiterhin wird durch Anwendung des Verfahrens auf chlor-, chlordioxid- und chlorithaltiges Trinkwasser gezeigt, daß Chlordioxid durch oxydable Inhaltsstoffe des Trinkwassers gewöhnlich nur bis zur Stufe des Chlorits reduziert wird.

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Summary A method currently used for determining chlorine, chlorine dioxide and chlorite in water is checked and discussed critically. A new method of analysis is described. Incorrect results hitherto obtained are avoided by combining the colorimetric determination of chlorine according to Asmus and Garschagen ¹ (1953) with two potentiometric titrations. Each of the three constituents in concentrations of 0.03 to 2 ppm total available chlorine are determined in utilizing this procedure. Moreover the application of this method to drinking water treated with chlorine, chlorine dioxide and chlorite indicates that chlorine dioxide is reduced usually by oxidizable substances of drinking water only to the stage of chlorite and not to chloride.

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Den Herren Prof. Dr. Naumann, Prof. Dr. Höfer und Dr. Kempf habe ich für anregende Diskussionen und Förderung der Arbeit sehr zu danken.