Mechanism for the radiolytic conversion of sulphur dioxide to sulphuric acid

The present paper describes the radiolytic oxidation of 10^-4M K₄[Fe(CN)₆] aqueous aerated solution in the presence of different concentrations of SO₂. In the absence of SO₂, ferrocyanide is oxidized to ferricyanide with a G value of 7.2. In this solution two O₂^- react to form H₂O₂. Ferrocyanide is oxidized by OH and H₂O₂ both. At low concentration of SO₂, O₂^- reacts with SO₂ forming first SO₄^._, which leads to chain oxidation of SO₂. The G [Fe(CN)₆^3-) decrease from 7.2 to 4.5. At higher concentrations of SO₂, H₂O₂ also reacts with SO₂ and the G(Fe(CN)₆^3-] further reduces to 2.7. In the presence of chloride ions, SO₄^._ converts them to chloride atoms which react with H₂O₂ and ferrocyanide and the G[Fe(CN)₆^3-] is again increased to 4.3. The reaction of OH with SO₂ was observed only at high concentrations of SO₂ since the reaction of OH with ferrocyanide is very fast. The importance of water and ammonia in the conversion of sulphur dioxide to sulphuric acid probably lies in their reaction with SO₄^2- to form H₂SO₄ or (NH₄)₂SO₄.     

A pulse radiolysis and flash photolysis study of the radicals SO-2, SO-3, SO-4 and SO-5

Pulse radiolysis and laser-flash photolysis have been used to generate the radicals SO^-₂, SO^-₃, SO^-₄ and SO^-₅. Optical absorption spectra for these radicals and rate constants for their self-reactions have been derived. The decay of SO^-₂, SO^-₃, and SO^-₄ follow simple second-order kinetics; the decay of SO^-₅ is slower and does not follow a second-order rate law when the radical is generated by the pulse radiolysis of an oxygenated sulfite or bisulfite solution, but is second-order when generated by the flash photolysis of an oxygenated dithionate solution. SO^-₂ reacts rapidly with O₂ and a rate constant of 2.4 × 10⁹ M^-1 s^-1 was derived. SO^-₃ also reacts rapidly with O₂ and a rate constant of 1.1 × 10⁹ M^-1 was derived for this reaction. The rate constant for the reaction of H with SO₂ was determined to be 2.9 × 10⁹ M^-1 s^-1.     

SPECTROSCOPIC STUDIES OF CUTANEOUS PHOTOSENSITIZING AGENTS—I. SPIN TRAPPING OF PHOTOLYSIS PRODUCTS FROM SULFANILAMIDE, 4-AMINOBENZOIC ACID AND RELATED COMPOUNDS

The photodecomposition of sulfanilamide, 4-aminobenzoic acid and other related analogs has been studied with the aid of the spin trap 2-methyl-2-nitrosopropane. UV photolysis of an aqueous solution of sulfanilamide yielded the following radicals C˙₆H₄SO₂NH₂, C₆H₅SO_2˙, S˙O₂NH₂ and SO^-_#˙ (or SO^-_2dot;). Under the same conditions 4-aminobenzoic acid gave C˙₆H₄COOH. In addition both sulfanilamide and 4-aminobenzoic acid, but not 4-dimethylaminobenzoic acid, generated e^-_aq or hydrogen atoms during UV irradiation. The C₆H₄SO₂NH₂ radical was also produced by photolysis of 4-iodobenzenesul-fonamide and 4-nitrobenzenesulfonamide. The C₆H₄COOH radical was generated by photolysis of 4-nitrobenzoic acid and 4-iodobenzoic acid. Finally the C₆H₄NO₂ radical was formed during the irradiation of 4-nitroaniline, 1,4-dinitrobenzene and 4-iodonitrobenzene. The free radicals generated by sulfanilamide and 4-aminobenzoic acid may play an important role in the phototoxic and photoallergic responses elicited by these drugs in certain individuals.     

Structural control in palladium(II)-catalyzed enantioselective allylic alkylation by new chiral phosphine-phosphite and pyridine-phosphite ligands

The ligands 6-[(diphenylphosphanyl)methoxy]-4,8-di-tert-butyl-2,10-dimethoxy-5,7-dioxa-6-phosphadibenzo[a,c]cycloheptene, 1, (S)-4-[(diphenylphosphanyl)methoxy]-3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4a′]dinaphthalene, (S)-2, and (S)-4-[(diphenylphosphanyl)methoxy]-2,6-bis-trimethylsilanyl-3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4-a′]dinaphthalene, (S)-3, (S)-2-(3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4-a′]dinaphthalen-4-yloxymethyl)pyridine, (S)-4, and (S)-2-(3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4-a′]dinaphthalen-4-yloxy)pyridine, (S)-5, have been easily prepared.The cationic complexes [Pd(η³-C₃H₅)(L-L′)]CF₃SO₃ (L–L′=1–(S)-5) and [Pd(η³-PhCHCHCHPh)(L–L′)]CF₃SO₃ (L–L′=(S)-2–(S)-4) were synthesized by conventional methods starting from the complexes [Pd(η³-C₃H₅)Cl]₂ and [Pd(η³-PhCHCHCHPh)Cl]₂, respectively. The behavior in solution of all the π-allyl- and π-phenylallyl-(L–L′)palladium derivatives 6–14 was studied by ¹H, ³¹P{¹H}, ¹³C{¹H} NMR and 2D-NOESY spectroscopy. As concerns the ligands (S)-4 and (S)-5, a satisfactory analysis of the structures in solution was possible only for palladium–allyl complexes [Pd(η³-C₃H₅)((S)-4)]CF₃SO₃, 11, and [Pd(η³-C₃H₅)((S)-5)]CF₃SO₃, 12, since the corresponding species [Pd(η³-PhCHCHCHPh)((S)-4)]CF₃SO₃, 13, and [Pd(η³-PhCHCHCHPh)((S)-5)]CF₃SO₃, 14, revealed low stability in solution for a long time. The new ligands (S)-2–(S)-5 were tested in the palladium-catalyzed enantioselective substitution of (1,3-diphenyl-1,2-propenyl)acetate by dimethylmalonate. The precatalyst [Pd(η³-C₃H₅)((S)-2)]CF₃SO₃ afforded the allyl substituted product in good yield (95%) and acceptable enantioselectivities (71% e.e. in the S form). A similar result was achieved with the precatalyst [Pd(η³-C₃H₅)((S)-3)]CF₃SO₃. The nucleophilic attack of the malonate occurred preferentially at allylic carbon far from the binaphthalene moiety, namely trans to the phosphite group. When the complexes containing ligands (S)-4 and (S)-5 were used as precatalysts, the product was obtained as a racemic mixture in high yield. The number of the configurational isomers of the Pd-allyl intermediates present in solution in the allylic alkylation and the relative concentrations are considered a determining factor for the enantioselectivity of the process.     

Diffusion and Ion Association in Concentrated Solutions of Aqueous Lithium, Sodium, and Potassium Sulfates

Taylor dispersion is used to measure mutual diffusion coefficients for aqueous Li₂SO₄ solutions at concentrations from 0.09 to 2.62 mol-dm^-3 at 25°C. The Li₂SO₄ results and previously reported diffusion coefficients for aqueous Na₂SO₄ and K₂SO₄ are compared with predictions made by treating the limiting electrolyte diffusion coefficients as reference values and applying corrections for nonideal solution behavior, ionic hydration, and viscosity changes as the concentration is raised. Good agreement is obtained if the M⁺ + SO ₄ ^2- ? MSO ₄ ^- (M = Li, Na, K) association equilibria are included in the analysis. Extents of formation of the MSO ₄ ^- ion pairs are evaluated by fitting Pitzer's mixed electrolyte equations for aqueous M⁺–MSO ₄ ^- –SO ₄ ^2- ions to osmotic coefficient data. Diffusion coefficients for hypothetical solutions of the completely dissociated M₂SO₄ electrolytes are calculated to illustrate the effects of ion association on diffusion. Association of the M⁺ and SO ₄ ^2- ions increases the overall mobility and thermodynamic driving forces for their diffusion.     

Structural Chemistry of Cu(I) Allyl and Acetylene π-Complexes

Stereospecific behavior of allyl derivatives and acetylenes in CuX -complexes (X = Cl^-, Br^-, NO₃ ^-, BF₄ ^-, 1/2SiF₆ ^2-, 1/2SO₄ ^2-) is studied by X-ray diffraction analysis. The influence of donor atoms N, S, and O and of the Cu-X bond polarization on the -complex formation is considered. The efficiency of Cu-(C=C) and Cu-(CC) -interaction and specific behavior of mono- and disubstituted acetylenes with respect to Cu(I) are compared.     

Nanocomposite Polymer Electrolytes for the Lithium Power Sources (a Review)

Nanocomposite polymer electrolytes represent a perspective class of polymer electrolytes for electrochemical devices in which nanodisperse filler is introduced to the “solvating matrix + lithium salt” base composition. This three-section paper reviews studies devoted to the preparing and investigating of different types of novel nanocomposite polymer electrolytes for lithium power sources carried out for the last 15 years. Its first section is devoted to the solid nanocomposite polymer electrolyte consisting of polyethylene oxide, lithium salt, and nanodisperse filler (Al₂O₃, TiO₂, SiO₂, etc.); the second section, to nanocomposite polymer membranes based on the polyvinylidene fluoride-co-hexafluoropropylene that can be used as a substitute for inert polyolefine separator of polypropylene, polyethylene, or their alternating layers. It is this type of the nanocomposite polymer electrolytes that is the most perspective one; the great majority of publications are dedicated to this electrolyte. The third section of the review covers the studies of the nanocomposite polymer electrolytes based on different polymers, oligomers, and co-polymers prepared by different methods. Nanoparticles of Al₂O₃, TiO₂, SiO₂, ZnO, MgO, Fe₃O₄, Ca₃(PO₄)2, ZrO₂, clay, ferroelectric ceramics SrBi₄Ti₄O₁₅, a compound SO₄^2-–ZrO₂, molecular sieves, nanochitin, etc., are discussed as possible additives to the nanocomposite polymer electrolytes. The reference list contains 101 items.     

Influence of Adding SiO2 into ZrO2 on SO2-4/ZrO2 Solid Superacid

用共沉淀法和负载法制备了一系列SO     

The determination of nitrite by ultraviolet absorption spectrometry in the gas phase

Aliquots of nitrite-containing solutions are injected into small aliquots of 8 M hydrochloric acid and the evolved gases are swept by a stream of carrier gas through an absorption cell where transient absorbance in the gas phase is measured at 195 nm. The detection limit is 0.2 μg NO₂^- ml^-1 with the calibration curve remaining linear to 65 μg NO₂^- ml^-1 Reproducibility is reflected in 2.4% relative standard deviation from the mean at the 5 μg NO₂^- ml^-1 level. There is no interference from CO₃^2-, NO₃^-, SO₄^2-, Br^-, CN^-, CNO^-, or NH₄⁺, but SCN^-, I^-, S^2- and SO₃^2- interfere.     

BIOLOGICAL DEACTIVATION AND SINGLE-STRAND BREAKAGE OF PLASMID DNA BY PHOTOSENSITIZATION USING TRIS(2,2''- BIPYRIDYL)RUTHENIUM(II) AND PEROXYDISULFATE

Abstract— Single-strand break formation and biological deactivation of plasmid pBR322 DNA in the presence of tris(2,2′-bipyridyl)-ruthenium(II), Ru(bpy)2/3;⁺, and K₂S₂O₈, upon irradiation with visible light(400–500 nm), were studied in aqueous solution at room temperature. Conditions of complete binding of Ru(bpy)2/3;⁺ to the strand were employed. The damage is initiated mainly by the SO^2/3;; radical anion. Under anoxic conditions at a ratio of nucleotide to sensitizer concentrations (N/S) of 18 and S₂O2/8^- concentrations of 0.5 mM the quantum yield of single-strand break (ssb) formation is φ_ssb= 8.4 times 10^-3 while that of biological deactivation (bd) is Ø_bd= 7.6 times 10^-3 (φ_ssb= 5.2 times 10^-36.4 times 10^-3, 6.0 times 10^-3 and φ_bd= 4.2 times 10^-3, 5.2 times 10^-3, 4.8 times 10^-3 at N/S=3, 6, and 9, respectively). The quantum yields are approximately 2.5 times smaller in air-saturated solutions. At N/S = 18 about 33 SO₄^-radical anions are required per one lethal event. φ_bd increases linearly with the S₂Oφ^- concentration (up to 0.5 mM). The damage to DNA is drastically reduced on addition of mono- or divalent salts (e.g. NaC10₄, MgCl₂). These additives cause the release of Ru(bpy)2⁺ from the strand. The observed damage to DNA is thus the result of a site specific reaction. When the phenanthroline analogue, Ru(phen)φ⁺, is used as sensitizer, φ_ssb and φ_bd are three times smaller.     

Binding of SO2 by Synthetic Substituted Apatites

The reaction of SO₂ with synthetic apatites was studied by TG, XRD and IR analyses at 400-1000°C. Due to an interaction of apatite with SO₂, destruction of apatite and formation of CaSO₄ and diphosphate up to 750°C takes place. The further calcination leads to the formation of β-Ca₃(PO₄)₂ and a part of the SO₂ bound is lost again. The amount of SO₂ bound with apatite at calcination depends on the substitution ((F^- ↔ OH^-, PO₄ ^3- ↔ CO₃ ^2-, Ca²⁺ ↔ Mg²⁺) in its structure. This revised version was published online in July 2006 with corrections to the Cover Date.     

Spotlight on the Effect of Electrolyte Composition on the Potential of Maximum Entropy: Supporting Electrolytes Are Not Always Inert

The influence of electrolyte pH, the presence of alkali metal cations (Na⁺, K⁺), and the presence of O₂ on the interfacial water structure of polycrystalline gold electrodes has been experimentally studied in detail. The potential of maximum entropy (PME) was determined by the laser-induced current transient (LICT) technique. Our results demonstrate that increasing the electrolyte pH and introducing O₂ shift the PME to more positive potentials. Interestingly, the PME exhibits a higher sensitivity to the pH change in the presence of K⁺ than Na⁺. Altering the pH of the K₂SO₄ solution from 4 to 6 can cause a drastic shift in the PME. These findings reveal that, for example, K₂SO₄ and Na₂SO₄ cannot be considered as equal supporting electrolytes: it is not a viable assumption. This can likely be extrapolated to other common “inert” supporting electrolytes. Beyond this, knowledge about the near-ideal electrolyte composition can be used to optimize electrochemical devices such as electrolyzers, fuel cells, batteries, and supercapacitors.     

Hydrolytic Polycondensation of Ethyl Silicate with Copper Salts of Mineral and Organic Acids in Sol-Gel Process

The structure and composition of polyheterosiloxanes formed in hydrolytic polycondensation of ethyl silicate in the presence of copper salts under the conditions of base catalysis (NH₄OH) were studied as influenced by the nature of acid anion (SO₄ ^{2 -}, Cl^-, NO₃ ^-, CH₃COO^-).     

Study on the reactions of fluoroalkanesulfonyl azides with pyrazine and its derivatives

The thermal reactions of fluoroalkanesulfonyl azides R_fSO₂N₃ with pyrazine and its derivatives are studied in detail. All the reactions involved the fluoroalkanesulfonyl nitrene intermediates R_fSO₃N: which was captured by pyrazine to give the pyrazinium N-fluoroalkanesulfonyl ylides C₄NH₄N⁺-⁻NSO₂R_f and hydrogen abstraction product R_fSO₂NH₂, but no corresponding N-pyrazinyl fluoroalkanesulfonyl amide derivatives R_fSO₂NHC₄N₂H₃ were isolated. Excess azides did not afford the bisN-ylide product R_fSO₂N⁻-⁺NC₄H₄N⁺-⁻NSO₂R_f.     

Removal of sulfate from wastewater via synthetic Mg–Al layered double hydroxide: An adsorption,kinetics, and thermodynamic study

Sulfate-contaminated water is a major environmental problem that alters the taste of water, disturbs the digestive systems of animals and humans, and erodes both soil and metals. In this study, the layered double hydroxide LDH 4Mg2Al·NO₃ and LDH 8Mg2Al·NO₃ were prepared using a co-precipitation technique, and applied in the adsorption of SO₄^2- from an aqueous solution. The reaction is well described by the Langmuir adsorption model. LDH 4Mg2Al·NO₃ and LDH 8Mg2Al·NO₃ afforded maximum SO₄^2- adsorption values of 135.14 and 92.59 ​mg/g, respectively. The reaction is best explained by a pseudo-second-order mechanism, which suggests that chemisorption is the rate-determining step. The activation energies of LDH 4Mg2Al·NO₃ and LDH 8Mg2Al·NO₃ indicate that the adsorption of SO₄^2- on synthetic LDHs predominantly follows an anion-exchange mechanism, wherein SO₄^2- ions in the aqueous medium replaces intercalated NO₃^- ions in the synthetic LDHs. The thermodynamic parameters (ΔH̊, ΔS̊, and ΔG̊) were also calculated. The reaction was endothermic, and the synthetic LDHs afforded feasible and spontaneous adsorption of SO₄^2-.     

Strained Ruthenium Complexes Bearing Tridentate Guanidine-Derived Ligands

The dimer [{(η⁶-p-cymene)RuCl}₂(μ-Cl)₂] (cymene=MeC₆H₄ⁱPr) reacts with N,N′-bis(p-tolyl)-N′′-(2-pyridinylmethyl)guanidine ( H₂L1 ) and N,N′-bis(p-tolyl)-N′′-(2-diphenylphosphanoethyl)guanidine ( H₂L2 ), in the presence of NaSbF₆, giving rise to chlorido compounds of formula [(η⁶-p-cymene)RuCl( H₂L )][SbF₆] ( H₂L = H₂L1 ( 1 ), H₂L2 ( 2 )) in which the guanidine ligand adopts a κ² chelate coordination mode. The related ligand (S)-N,N′-bis(p-tolyl)-N′′-(1-isopropyl, 2-diphenylphosphano ethyl)guanidine ( H₂L3 ) affords mixtures of the corresponding chlorido compound [(η⁶-p-cymene)RuCl( H₂L3 )][SbF₆] ( 3 ) together with the complexes [(η⁶-p-cymene)RuCl₂( H₃L3 )][SbF₆] ( 4 ) and [(η⁶-p-cymene)Ru(κ³N,N′,P- HL3 )][SbF₆] ( 10 ) which contain phosphano-guanidinium and phosphano-guanidinate ions acting as monodentate and tridentate ligand, respectively. Compounds 1 , 2 and mixture of 3 / 4 / 10 react with AgSbF₆ rendering the cationic aqua-complexes [(η⁶-p-cymene)Ru( H₂L )(OH₂)][SbF₆]₂ ( H₂L = H₂L1 ( 5 ), H₂L2 ( 6 ), H₂L3 ( 7 )). These aqua-complexes exhibit a temperature-dependent fluxional process in solution. Experimental NMR studies and DFT theoretical calculations on complex 6 suggest that the process involves the exchange between two rotamers around one of the C−N guanidine bonds. Treatment of 5 – 7 with NaHCO₃ renders the complexes [(η⁶-p-cymene)Ru(κ³N,N′,N′′- HL1 )][SbF₆] ( 8 ) and [(η⁶-p-cymene)Ru(κ³N,N′,P- HL )][SbF₆] ( HL = HL2 ( 9 ), HL3 ( 10 )), respectively, in which the HL ligand adopts a fac κ³ coordination mode. The new complexes have been characterized by analytical and spectroscopic means, including the determination of the crystal structures of the compounds 1 , 2 , 5 , 9 and 10 , by X-ray diffractometric methods.     

Study on phase diagrams and properties of solutions in ternary systems Li+,K+(Mg2+)/SO42--H2O at 25°C

Solubilities of ternary systems Li⁺,K⁺/SO^2-₄-H₂O (1) and Li⁺,Mg²⁺/SO₄^2--H₂O (2) were investigated by isothermal method at 25°C. Physico-chemical properties of solutions, such as density, refractive index, viscosity, conductivity and pH, were determined. Phase diagram of the system (1) consists of three solubility branches and three crystallization fields corresponding to K₂SO₄, Li₂SO₄·H₂O and LiKSO₄. LiKSO₄ is an incongruent compound, and its transition point is estimated graphically to be 45.5–46.0°C. No solid solution of LiKSO₄ with Li₂SO₄·H₂O was found in the system. The system (2) is a simple eutonic type. Pitzer model of electrolyte solution was used to check the obtained solubilities. Data comparison gives good agreement. Two equations were used to correlate density, refractive index of the solution with its composition. Differences between measured and calculated values are less than 0.6% for density, 0.15% for the latter.     

Effects of different oxygen-containing anions on the structure of water clusters

Using Ni(Im)₆²⁺ (Im = imidazole) as the structural unit, the effects of oxygen-containing anions, such as SO₄^2-, NO₃^? and CO₃^2- on the structure of water clusters were studied. The crystal structures of three compounds [Ni(Im)₆][SO₄(H₂O)₁₁] (1), [Ni(Im)₆][(NO₃)Cl(H₂O)₄] (2), and [Ni(Im)₆][CO₃(H₂O)₅] (3) were obtained. Using Mercury-3.8 software to analyze the above three crystal structures, find different anion of water clusters had a significant effect on the supramolecular structure. At the same time, it also significantly influences the number of water molecules in the crystal structure.     

Electron transfer. 154. Reaction of the nitrosodisulfonate anion radical with one- and multi-electron inorganic reductants

The nitrosodisulfonate anion radical, NO(SO₃)₂ ^2-, a single electron oxidant, reacts cleanly with an array of metal-center reductants. Rates for substitution-labile species generally fall in the range 10⁴ -10⁵ M^-1 s^-1, both for le^-[Eu^II, Fe^II(EDTA)] and 2e^-(U^IV, In^I, Ge^II and Sn^II) reagents. The more weakly reducing donor VO²⁺ reacts more slowly (3 M^-1 s^-1 at 22°C) and the substitution-inert complex Fe(CN)₆ ^4- still more sluggishly. Reductions with the non-metal related donors, azide, formate, hypophosphite, hyponitrite and H2₂AsO₃ ^-, fall in the range 10^-4 -10^-2 M^-1 s^-1. Reactions yield the product HON(SO₃)₂ ^2-. Kinetic decay curves feature no irregularities reflecting formation or loss of one or more transients on a time scale comparable to that of the main conversion, indicating that the experimental rates pertaining to the 2e reductants and to hydrazine (a 4e reductant) are determined by the initial le transfer and that follow-up steps are rapid. The usual distinction between complementary and noncomplementary redox reactions applies poorly to reductions of NO(SO₃)₂ ^2-. Rapid reductions require (1) an adequate potential difference, (2) the possibility of an inner-sphere path and (3) the availability of one or more nonbonding electrons at the reducing site. Substitution-labile metal-based reducing centers embracing a wide range of formal potentials, both le^- and 2e^- donors, may react speedily, although the latter group must operate in steps.     

Extraction and sorption preconcentration of rhenium with the use of 2-phosphorylphenoxyacetamides

Interfacial distribution of micro amount of ReO₄ ^- between aqueous solutions of mineral acids and solutions of 2-phosphorylphenoxyacetamides in dichloroethane has been studied. Stoichiometry of extracted complexes has been determined; the effect of HNO₃, HCl, and H₂SO₄ concentration in aqueous phase, extractant structure, and organic solvent nature on the efficiency of ReO₄ ^- ions transfer into organic phase has been considered. It has been shown that Re(VII) can be selectively recovered and concentrated with complexing sorbent obtained by the noncovalent binding of 2-[2-(diphenylphosphoryl)-4-ethylphenoxy]-N,N-dioctylacetamide on the surface of macroporous polymer Amberlite XAD7HP.