Flash Photolysis of Diphenyldiazomethane in the Presence of Organic Sulfides

The flash photolysis of diphenyldiazomethane in acetonitrile, benzene, and n-decane solutions saturated with air resulted in the formation of diphenyl carbonyl oxide Ph₂COO which decayed in combination reactions. In the presence of organic sulfides, the transfer of the terminal oxygen atom of Ph₂COO to the sulfur atom was observed. The kinetics of this reaction was studied. The absolute rate constants (k ₆, dm³ mol^–1 s^–1) of the reactions of Ph₂COO with sulfides at 295 K (acetonitrile as a solvent) varied from 4.1 × 10² (Me₂S) to 8.1 × 10⁴ (Ph₂S). The solvent effect on the reaction kinetics and product composition was studied. The mechanism of the process was discussed.     

Determination of the Absolute Rate Constants of Reactions between Diphenyl Carbonyl Oxide and Alcohols by Flash Photolysis

The rate constants of the reactions of diphenyl carbonyl oxide Ph₂COO with a number of alcohols and water in acetonitrile, benzene, andn-decane solutions (295 K) were measured by flash photolysis. The rate constants vary over a range from 400 (triphenylmethanol in a MeCN solution) to 2.5 × 10⁵ l mol^–1 s^–1 (adamantanol in a benzene solution). -Methoxydiphenylmethyl hydroperoxide is the reaction product of Ph₂COO and MeOH. The absence of a kinetic isotope effect and the dependence of the logarithms of the rate constants on the first ionization potentials of alcohols are indicative of the formation of a C–O bond at the rate-limiting step of the reaction.     

Rate Constants for the Reaction of Diphenyl Carbonyl Oxide with Phenols

The kinetics of the reaction of diphenyl carbonyl oxide Ph₂COO with o- and p-substituted phenols is studied by pulse photolysis and high-speed spectrophotometry. The rate constant strongly depends on the phenol structure and ranges from 1.3 × 10³ for ionol to 2.1 × 10⁸ l mol^–1 s^–1 for o-aminolphenol. A U-shaped curve illustrating how the logarithm of the rate constant changes with a change in the Hammett constants (⁰) of the substituents in the aromatic ring is found for the studied compounds. Possible pathways for the reaction of Ph₂COO with phenols are discussed.     

The Reactivity of Diphenyl Carbonyl Oxide in Reactions with Alcohols

The reactivities of ten alcohols in the reactions with diphenyl carbonyl oxide Ph₂COO is characterized by the ratio k ^OH ₃₃ /k ₃₁, where k ^OH ₃₃ and k ₃₁are the rate constants of Ph₂COO reactions with an alcohol and diphenyldiazomethane PH₂CN₂, respectively. The values of k ^OH ₃₃ /k ₃₁range between 0.6 × 10^–2for MeOH to 6.0 for iso-PrOH at 70°C in acetonitrile. The donation of electron density to the alcohol hydroxyl group favors the attack of Ph₂COO; that is, Ph₂COO reacts as an electrophile.     

Kinetics and mechanism of distribution of Am(III) and Eu(III) between thenoyltrifluoroacetone-triphenylarsine oxide mixture in chloroform and aqueous nitrate medium

The kinetics of distribution of Am(III) and Eu(III) between thenoyltrifluoroacetone (HTTA) and triphenylarsine oxide (Ph₃AsO) mixture in chloroform and aqueous nitrate medium has been investigated using a stirred Lewis cell at ionic strength of 0.1M. The effect of the concentration of HTTA, Ph₃AsO, H⁺ and NO ₃ ^– on the rate of distribution of Am(III) and Eu(III) was studied. The results were interpreted by reaction mechanisms where the rate-determining steps are the parallel reactions of Am(OH)²⁺ or Eu(OH)²⁺ with one HTTA molecule and one Ph₃AsO molecule in the aqueous medium. The values at 25 °C of the rate constantk _HLL (HL=HTTA andL=Ph₃AsO) are 1.6±0.3·10⁶M^–2·s^–1 and 2.3±±0.3·10⁸M^–2·s^–1 for Am(III) and Eu(III), respectively.     

Kinetics, products, and mechanism of the reaction of diphenylcarbonyl oxide with sulfoxides

The kinetics of the reactions of diphenylcarbonyl oxide with dimethyl, di-n-hexyl, diphenyl, dibenzyl, andn-hexylbenzyl sulfoxides in acetonitrile was studied by flash photolysis at 295 K. The oxidation of sulfoxide affords the corresponding sulfone as the main reaction product, and diphenyl sulfide also forms in the case of Ph₂SO. Solvent effect on the reaction kinetics and the composition of the reaction products was studied. The reaction mechanism is discussed, which includes two parallel pathways: the nucleophilic attack of carbonyl oxide at the sulfur atom of sulfoxide and the formation of the cyclic sulfurane intermediatevia the electrophilic 1,3-cycloaddition of Ph₂COO at the S=O bond. The sulfurane undergoes fragmentationvia parallel channels to form sulfone or sulfide. Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1504–1509, September, 2000.     

Reactions of the radial cattions of acetic acid and acetic anhydride in CFCl3

The ESR spectra of -irradiated, at –196 °C, solutions of acetic acid and acetic anhydride were studied depending on their concentrations in CFCl₃. The structure of thus produced radical cations is confirmed with the deuterium substituted analogues. It has been shown that the ion-molecular reaction of the radical cation CH₂COOH⁺ in the isolated dimer takes place for the dilute solutions of acetic acid in CFCl₃ resulting in the formation of CH₃COO follwed by its decomposition to CH₃+CO₂ while the radicals CH₂COOH are formed via secondary processes. The reactions of radical cations of acetic oxide have been also studied.     

Reaction of triphenylantimony and triphenylbismuth withtert-butyl peracetate

Triphenylantimony and triphenylbismuth diacetates, Ph₃M(OAc)₂ (M = Sb, Bi), were obtained in 50–94 % yields by the reaction of triphenylantimony and triphenylbismuth withtert-butyl peracetate in the presence of acetic acid or acetic anhydride (molar ratio 1 1 1) in toluene.tert-Butyl peracetate oxidizes Ph₃M into alkoxides, Ph₃M(OAc)OBu^t, which at the instant of formation are acylated with acetic acid or acetic anhydride to give the corresponding derivatives, Ph₃M(OAc)₂.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 964–967, May, 1995.This study was financially supported by the Russian Foundation for Basic Research (Grant 94-03-08846).     

Reactivity of aromatic compounds toward diphenylcarbonyl oxide

The reactivity of organic compounds (PhH, PhMe, PhF, PhCl, PhOH, PhOEt, PhCHO, Ph₂CO, PhCN, Ph₂S, Ph₂SO, Ph₂SO₂, andp-Me₂C₆H₄) toward diphenylcarbonyl oxide Ph₂COO was characterized by thek ₃₃/k ₃₁ ratio, wherek ₃₃ andk ₃₁ are the rate constants for the reactions of Ph₂COO with the arene and diphenyldiazomethane Ph₂CN₂, respectively. The values ofk ₃₃/k ₃₁ vary from 2.6·10⁻³ (PhCN) to 0.65 (Ph₂S) (70°C, MeCN). The reaction is preceded by formation of a complex with charge transfer from a substrate to Ph₂COO. In the reactions with aromatic substances (except for Ph₂SO, PhCHO, and Ph₂CO), carbonyl oxide behaves as an electrophile. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2197–2201, November, 1998.     

Synergistic extraction of cobalt(II) with oxine/decanoic acid solution mixtures in benzene and chloroform

Synergistic extraction of Co(II) with 8-hydroxyquinoline (Hq)/decanoic acid [(HR)₂] solution mixtures in benzene and chloroform was carried out at 25°C. The aqueous ionic strength and the total concentration of cobalt(II) were 0.1 (NaCl) and 1·10^–5–1·10^–3M, respectively. The synergistic effect is interpreted by the formation of the mixed ligand ion-pair complexes: [(Coq(Hq)₂(HR))⁺, R^–] and [(Coq(Hq)₂(HR)₃)⁺, R^–] in benzene and chloroform, respectively.     

Specifics of Interaction of Acetone Molecules with Quasi-free Electrons: Analysis of Positron Annihilation Characteristics in Aqueous and Alcoholic Acetone Solutions

The yields of formation of radiolytic hydrogen (H₂) and orthopositronium (o-Ps) in aqueous and alcoholic acetone solutions were experimentally determined. A decrease in the o-Ps yield with an increase in the acetone concentration is much weaker than the decline in the yield of solvated electrons (e^– _s) under picosecond pulse radiolysis conditions. In contrast, the decrease in the o-Ps yield is minimal in higher alcohols where the inhibiting action of acetone e^– _s is most pronounced. These findings seem to contradict the conventional concepts of Ps formation via the intratrack reaction of positron recombination with a track electron (e^–), which competes with the reaction of e^– scavenging by dissolved acetone molecules. This contradiction can be eliminated, assuming that the scavenging of e^– by acetone begins from the formation of the weakly bound transient state (CH₃)₂CO···e^– capable of donating e^– to a positron. This opens up an additional pathway for the formation of the Ps atom.     

Extraction and spectrophotometric determination of uranium in phosphate fertilizers

An extraction and spectrophotometric method for determination of trace amounts of uranium in phosphate fertilizers is described. It is based on the extraction of uranium with trioctylphosphine oxide in benzene and the spectrophotometric determination of uranium with Arsenazo III in buffer-alcoholic medium. The maximum absorbance occurs at 655 nm with a molar absorptivity of 1.2·10⁴ l·mol^–1·cm^–1. Beer's law is obeyed over the range 0.6–15.0 g·ml^–1 of uranium(VI). The proposed method has been applied successfully to the analysis of phosphate fertilizers with phosphate concentrations of 45% P₂O₅.     

Reaktion von Phosphinboran,Phenylphosphinboran und Phosphoniumjodid mit Natriumtetrahydridoborat

Zusammenfassung Phosphinboran und Phosphoniumjodid reagieren mit NaBH₄ unter H₂-Entwicklung zu H₂P(BH₃)₂–Na⁺(I), Phenylphosphinboran zuPhHP(BH₃)₂–Na⁺ (II). Methylphosphinboran, Phenylphosphin und die Anionen von I und II reagieren nicht mit NaBH₄, da die Acidität des an Phosphor gebundenen Wasserstoffs zu gering ist. Auch (PhHP·BCl₂)₃ reagiert mit NaBH₄ unter Wasserstoffentwicklung.

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Reaction of phosphine borane, phenylphosphine borane and phosphonium iodide with sodium tetrahydridoborate

The reaction of phosphine borane and phosphonium iodide with NaBH₄ yields H₂P(BH₃)₂–Na⁺ (I), of phenylphosphine boranePhHP(BH₃)₂–Na⁺ (II) hydrogen being evolved in both reactions. Methylphosphine borane, phenylphosphine and the anions of I and II do not react with NaBH₄ on account of the reduced acidity of the hydrogen atoms bound to phosphorus. Likewise hydrogen is evolved if (PhHP·BCl₂)₃ reacts with NaBH₄.

     

On the characteristics and mechanism of the radiation-induced chain reaction between sulfur dioxide and molecular oxygen in acid solutions

Characteristics of the -induced chain reaction between sulfur dioxide and molecular oxygen in perchloric and sulfuric acid media in the presence of Ce(III) ions have been studied. The concentration effects of dissolved oxygen (0.2·10^–3–9.4·10^–3 mol/dm³, sulfur dioxide (0.3·10^–1–2.0·10^–1 mol/dm³ and Ce(III) (0.2·10^–3–4.8·10^–3 mol/dm³) and dose rate (0.26·10¹⁹–1.0·10¹⁹ eV/dm³·s) on the radiation — chemical yield of oxygen consumption G(–O₂) and accumulation of sulfate G(HSO ₄ ^– ), have been investigated. The reaction proceeds with G(–O₂) reaching 10²–10³ molecule/100eV in a catalytic regime. The reaction rate in perchloric acid medium is 3–4 times lower than that in the sulfuric acid medium and depends on the SO₂, O₂ and Ce(III) concentrations, the reaction order varying from 1.0 to 0 and/or in the reverse direction. The mechanism of the process involves chain propagation with 3 stages and 3 intermediates: SO₃H, HSO₅ and Ce(IV). The catalytic effect is caused by the interaction of HSO₄ with Ce(IV) ions followed by their reduction when interacting with SO₂, yielding SO₃H radicals. Chain termination may be due to one or two of the three intermediates or due to all three particles, the kinetics depending on this. Kinetic equations describing the experimental data have been obtained.     

Solvent effects on the absorption spectrum and recombination kinetics of diphenylcarbonyl oxide

The absorption spectra and rate constants of diphenylcarbonyl oxide recombination in a series of solvents and their binary mixtures were determined by flash photolysis. An increase in the solvent polarity causes hypsochromic shift of the maximum in the absorption spectrum of Ph₂COO. The analysis of the solvent effect on the recombination rate constant in terms of the four-parameter Koppel—Palm equation shows that the reactivity of carbonyl oxide depends on both specific and non-specific solvations. Quantum chemical B3LYP/6-31G(d) calculations of H₂COO and PhHCOO carbonyl oxides as well as the complexes of H₂COO with acetonitrile and ethylene in different media were performed using a polarized continuum model.     

Kinetic investigation of sulfur(IV) oxidation by peroxo compounds R-OOH in aqueous solution

Summary Normal and rapid-scan stopped-flow spectrophotometry in the range of 260–300 nm was used to study the kinetics of sulfur(IV) oxidation by peroxo compounds R-OOH (such as hydrogen peroxide, R=H; peroxonitrous acid, R=NO; peroxoacetic acid, R=Ac; peroxomonosulfuric acid, R=SO ₃ ^– ) in the pH range 2–6 in buffered aqueous solution at an ionic strength of 0.5 M (NaClO₄) or 1.0 M (R=NO; Na₂SO₄). The kinetics follow a three-term rate law, rate=(k_H[H]+k_HX[HX]+k_p)[HSO ₃ ^– ][ROOH] ([H] = proton activity; HX = buffer acid = chloroacetic acid, formic acid, acetic acid, H₂PO ₄ ^– ). Ionic strength effects (I=0.05–0.5 M) and anion effects (Cl^–, ClO ₄ ^– , SO ₄ ^2– ) were not observed. In addition to proton-catalysis (k_H[H]) and general acid catalysis (k_HX[HX]), the rate constant k_p characterizes, most probably, a water induced reaction channel with k_p=k_HOH[H₂O]. It is found that k_Hf(R) with k_H(mean)=2.1·10⁷ M^–2 s^–1 at 298 K. The rate constant k_HX ranges from 0.85·10⁶ M^–2 s^–1 (HX=ClCH₂–COOH; R=NO; 293 K) to 0.47·10⁴ M^–2 s^–1 (HX=H₂PO ₄ ^– ; R=H; 298 K) and the rate constant k_p covers the range 0.2·M^–1 s^–1 (R=H) to 4.0·10⁴ M^–1 s^–1 (R=NO). LFE relationships can be established for both k_HX, correlating with the pK_a of HX, and k_p, correlating with the pK_a of the peroxo compounds R-OOH. These relationships imply interesting aspects concerning the mechanism of sulfur(IV) oxidation and the possible role of peroxonitrous acid in atmospheric chemistry. A UV-spectrum of the unstable peroxo acid ON-OOH is presented.     

Catalytic Oxidative Deformylation of Polyethylene Glycols with the Participation of Molecular Oxygen

The kinetics of oxidation of diethylene glycol, triethylene glycol, and polyethylene glycols (PEGs) with molecular weights ranging from 400 to 2000 in the presence of Cu(II) ions and bases was studied. It was found that ethylene glycols can be oxidized by molecular oxygen in anhydrous media in a temperature range of 30–60°C at anomalouosly high rates which are higher than the rates of chain-radical PEG autoxidation by several orders of magnitude. Only terminal hydroxyl groups were subjected to oxidation. The reaction occurs with the cleavage of a C–C bond and results in the formation of formic acid and a PEG with the number of –(CH₂CH₂O)– groups lower than that in the parent compound by unity. The rate and selectivity of PEG oxidation were found to strongly depend on the molecular weight of the polymer; from diethylene glycol to PEG 2000, the specific rate of oxidation increased by a factor of 60 in terms of terminal hydroxyl groups. An oxidation mechanism was suggested, which involves the formation of ternary complexes [Cu²⁺···A^–···O₂], which undergo further degradation by a many-electron concerted mechanism to form formic acid and, probably, an unstable hemiacetal {RO–CH₂OH}. The rapid oxidative degradation of the latter leads to the formation of PEG with a lower molecular weight.     

Adducts of Diethyldithiocarbamate Complexes of Zinc(II) and Copper(II) with Piperidine [M(Pip)(Edtc)2] and Their Solvated Forms [M(Pip)(Edtc)2] · L (L = C6H6, C5H5N,C4H9NO): Synthesis,EPR and Solid-State (13C, 15N) CP/MAS NMR Studies

Crystal adducts of diethyldithiocarbamate complexes of zinc(II) and copper(II) with piperidine (Pip) were synthesized, and their solvated forms with the outer-sphere molecules of benzene, pyridine (Py), and morpholine (Mf) were obtained. Adducts with composition [M(Pip)(Edtc)₂] · L (L = Py, Mf) were shown to be able, in principle, to give solvated isomers [M(L)(Edtc)₂] · Pip with the Pip molecule arranged in the outer sphere. The composition, structure, and properties of the obtained adducts were studied by EPR, high-resolution solid-state ¹³C, ¹⁵N NMR spectroscopy. Solvation of all three adducts with Pip, Mf, and Py was found to result in a substantial increase in the contribution of the trigonal–bipyramidal component to the geometry of a copper coordination pentahedron. In addition, for adducts with Mf and Py, a structural unification of two isomeric forms was observed at the molecular level to yield a qualitatively new (rather than intermediate) state. It was shown that in all solvated forms of the copper(II) adducts, the metal polyhedron is mainly a trigonal bipyramid, while the square–pyramidal contribution is insignificant. Results of (¹³C, ¹⁵N) NMR studies revealed a structural inequivalence of the Edtc^–ligands in the zinc adducts under investigation.     

Transfer Reactions of Rydberg (Quasi-Rydberg Molecular) Electrons in Condensed Media: IV. Large Proton Displacements upon Phosphorescence Quenching via Highly Excited Triplet States T* of Substituted Aromatic Solute Molecules in Solutions at 77 K

Intramolecular phosphorescence quenching via states T* in aromatic solute molecules containing N–H (diphenylamine (DPA) or carbazole), O–H (naphthol), etc. bonds was observed in methylcyclohexane at 77 K. The quantum yield of quenching measured for DPA increases with increasing the energy of the T* state. As in the case of external electron acceptors, the quenching and photodissociation are associated with the capture of excited * electrons onto polarized bonds N–H⁺, O–H⁺and with the formation of triplet complexes (for example, Ph₂N···H*, where H* is the excited hydrogen atom). The complexes can be deactivated via configurations with large proton displacement distances (Ph₂N^–···H⁺).     

Sorption of hafnium on hydrous titanium oxide using radiotracer technique

The sorption of hafnium on hydrous titanium oxide (TiO₂·1.94 H₂O) has been studied in detail. Maximum sorption of hafnium can be achieved from a pH 7 buffer solution containing boric acid and sodium hydroxide using 50 mg of the oxide after 30 minutes shaking. The value ofk _d, the rate constant of intraparticle transport for hafnium sorption, from 0.01M hydrochloric and perchloric acid and pH 7 buffer solutions has been found to be 17 mmole·g^–1·min^–2. The kinetics of hafnium sorption follows Lagergren equation in 0.01M HCl solution only. The values of the overall rate constantK=6.33·10^–2 min^–1 and of the rate constant for sorptionk ₁=6.32·10^–2 min^–1 and desorptionk ₂=2.28·10^–5 min^–1 have been evaluated using linear regression analysis. The value of correlation factor() is 0.9824. The influence of hafnium concentration on its sorption has been examined from 4.55·10^–5 to 9.01·10^–4 M from pH 7 buffer solution. The sorption data followed only the Langmuir sorption isotherm. The saturation capacity of 9.52 mmole·g^–1 and of a constant related to sorption energy have been estimated to be 2917 dm³·mole^–1. Among all the additional anions and cations tested only citrate ions reduce the sorption significantly. Under optimal experimental conditions selected for hafnium sorption, As(III), Sn(V), Co(II), Se(IV) and Eu(III) have shown higher sorption whereas Mn(II), Ag(I) and Sc(III) are sorbed to a lesser extent. It can be concluded that a titanium oxide bed can be used for the preconcentration and removal of hafnium and other metal ions showing higher sorption from their very dilute solutions. The oxide can also be employed for the decontamination of radioactive liquid waste and for pollution abatement studies.