Complex formation effects during the oxidation of cyclohexene with lead tetraacetate

The effect of complex formation between lead(IV) and trifluoroacetic or methanesulfonic acid and chloride ion in acetic acid and Freon 113 on the oxidation of cyclohexene by lead tetraacetate was investigated. As a result of the reaction the -chlorocyclohexyl esters of the corresponding acids are formed with high yields. The formation of the complexes Pb(OAc)_4–nL_n and Pb(OAc)_4–(n+1)L_nCl, where L = CF₃CO₂- or CH₃SO₃- with n=1 or 2, was demonstrated by potentiometric titration. A scheme is proposed for the oxidation of cyclohexene with the participation of unlike-ligand complexes of Pb(IV).Translated from Teoreticheskaya Eksperimental'naya Khimiya, Vol. 21, No. 5, pp. 567–572, September–October, 1985.     

Direct laser-chemical sensitized synthesis of formaldehyde from methane

An original method is proposed for the direct oxidation of methane to formaldehyde at room temperature and atmospheric pressure by atmospheric oxygen, under the action of a continuous tunable CO₂ laser. The synthesis is accompalished by a sensitized laser-chemical reaction due to intermodal vibrational activation of methane by V-V exchange with the sensitizer.Institute of General and Inorganic Chemistry, Ukrainian Academy of Sciences, Kiev. Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 27, No. 6, pp. 730–733, November–December, 1991. Original submitted March 27, 1991.     

On the energy transfer at the radiolysis of CO-H2S gas mixture

The kinetics of hydrogen formation at various amounts of H₂S /1–60%/ in the radiolysis of CO–H₂S mixture has been studied. The ratio of the reaction rate constants for reactions CO^x+COproduct and CO^x+H₂SH+SH=CO, which amounts to 5×10^–2, has been estimated. The effective activation energy of hydrogen formation /E_eff/ has been determined at various amounts of H₂S in the temperature interval 323–573 K.     

Ascorbate-induced oxidation of formate by peroxodisulfate: product yields,kinetics and mechanism

The slow reaction between peroxodisulfate and formate is significantly accelerated by ascorbate at room temperature. The products of this induced oxidation, CO₂ and oxalate (C₂O^2– ₄), were analyzed by several methods and the kinetics of this reaction were measured. The overall mechanism involves free radical species. Ascorbate reacts with peroxodisulfate to initiate production of the sulfate radical ion (SO^– ₄), which reacts with formate to produce carbon dioxide radical ion (CO^– ₂) and sulfate. The carbon dioxide radical reacts with peroxodisulfate to form CO₂ or self-combines to form oxalate. Competition occurring between these two processes determines the overall fate of the carbon dioxide radical species. As pH decreases, protonation of the carbon dioxide radical ion tends to favor production of CO₂.     

The rate constant of the reaction HO2 + COCO2 + OH

The high-temperature oxidation of formaldehyde in the presence of carbon monoxide was investigated to determine the rate constant of the reaction HO₂ + CO ? CO₂ + OH (10). In the temperature range of 878–952°K from the initial parts of the kinetic curves of the HO₂ radicals and CO₂ accumulation at small extents of the reaction, when the quantity of the reacted formaldehyde does not exceed 10%, it was determined that the rate constant k₁₀ is A computer program was used to solve the system of differential equations which correspond to the high-temperature oxidation of formaldehyde in the presence of carbon monoxide. The computation confirmed the experimental results. Also discussed are existing experimental data related to the reaction of HO₂ with CO.     

Extraktions-Flammenabsorptionsbestimmung von Spurenverunreinigungen in Salzen

Zusammenfassung Spurenverunreinigungen von Fe, Cu, Pb, Ni, Co, Cd, Zn wurden in KH₂PO₄, KNa-Tartrat, BaCl₂, CaCl₂, Citronensäure, Li₂CO₃, Na₂CO₃, K₂CO₃, BaCO₃ und CaCO₃ durch Flammenatomabsorption nach Extraktionsanreicherung mit Diethylammonium-N,N-diethyldithiocarbamat/MIBK bestimmt. Der Einfluß der Salz-matrix auf die Extraktion und Bestimmung der Elementspuren wurde untersucht. Die Methode erlaubt die Bestimmung von 5 · 10^–6–5 · 10^–7% der Elemente mit guter Präzision und Richtigkeit (rel. Standardabweichung 2–7%).

---

Extraction flame atomic-absorption determination of microtraces in salts

Summary The trace content of Fe, Cu, Pb, Ni, Co, Cd, Zn in KH₂PO₄, KNa-tartrate, BaCl₂, CaCl₂, citric acid, Li₂CO₃, Na₂CO₃, K₂CO₃, BaCO₃ and CaCO₃ is determined by flame atomic-absorption spectrometry after preceding preconcentration of the traces using the extraction system diethylammonium-N,N-diethyldithiocarbamate/ MIBK. The influence of the salt matrix on the extraction and determination of the traces was investigated. The method permits the determination of 5·10^–6–5·10^–7% of the elements with good precision and accuracy (relative standard deviation 2–7%).

     

Role of radical ions in the thermally stimulated luminescence of uranium doped BaCO3 system

Electron paramagnetic resonance (EPR) studies of -irradiated uranium doped BaCO₃ have shown the formation of CO₃ ^–, CO₂ ^–, O₃ ^– and O₂ ^– ions. Thermally stimulated luminescence (TSL) glow curves of the -irradiated samples in the 300–600 K range have exhibited an intense peak around 360 K and a weak one around 440 K. The trap parameters for these peaks have been determined from TSL data. Spectral studies of the glow have revealed emission around 566, 583 and 590 nm characteristic of the uranate ion. From studies on the thermal stabilities of the radical ions, it has been inferred that the glow peak around 360 K is associated with the thermal destruction of O₂ ^– ion and the peak around 440 K is associated with the thermal destruction of CO₃ ^– ion.     

Oxidation of Methanol on Pt,Pt–Ru,and Pt–Ru–Mo Electrocatalysts Dispersed in Polyaniline: An in situ Infrared Reflectance Spectroscopy Study

The electrochemical oxidation of methanol was investigated on a Pt–Ru–Mo catalyst with an in situ infrared reflectance spectroscopy. The electrocatalysts were prepared by an electrochemical deposition and dispersed in a conducting three-dimensional matrix of polyaniline (PAni). We observed that CO₂ is produced from methanol oxidation at 350 mV vs. RHE on PAni/Pt–Ru–Mo, which is 100 mV less negative than on PAni/Pt–Ru and 200 mV less than on PAni/Pt. The results suggest that Pt–Ru–Mo is less sensitive to CO_ADS poisoning than Pt–Ru and much more sensitive than Pt. Large differences are observed concerning the average wavenumber of _ADS between Pt–Ru–Mo, Pt–Ru, and Pt.     

Hydration of the carboxylate group: Anab initio molecular orbital study of acetate-water complexes

The hydration of the carboxylate group in the acetate anion has been investigated by performingab initio molecular orbital calculations on selected conformers of complexes with the form CH₃CO₂ ^– ·nH₂O·mH₂O, wheren andm denote the number of water molecules in the first and second hydration spheres around the carboxylate group, andn + m 7. The results of RHF/6–31G^* optimizations for all the complexes and MP2/6–31+G^** optimizations for several one-water complexes are reported. The primary consequence of hydration on the structure of the acetate anion is a decrease in the length of the C-C bond. Enthalpy and free energy changes calculated at the MP2/6–31+G^** and MP2/6–311+ +G^** levels are reported for the reactions CH₃CO₂ ^– + [H₂O] _P CH₃CO₂ ^– ·nH₂O ·mH₂O where [H₂O] _P is a water cluster containingp water molecules andp=n+m 7. The calculations show that conformers with the lowest enthalpy change on complex formation are often not those with the lowest free energy change, due to a greater entropic loss in complexes with tighter and more favorable enthalpic interactions. Hydrogen bonding of six water molecules directly to the carboxylate group in CH₃CO₂ ^– is found to account for approximately 40% of the enthalpy change and 37% of the free energy change associated with bulk solvation.     

Reaction of α,α,ω-trichloro- and α,α,α,ω-tetrachloroalkanes with alkali metal acylates in aprotic solvents

Polychloroalkanes and -alkenes R(CH₂)_nCl (R=CHCl₂CH₂, CCl₂=CH, n=1, 3) in dipolar aprotic solvents — dimethylformamide (DMF), dimethylsulfoxide (DMSO), hexamethylphosphoramide (HMPA) — at 130–150°C react selectively at the CH₂Cl group with salts of carboxylic acids RCO₂K(Na) to form dichloroesters RCO₂· (CH₂)_nR (R=CHCl₂CH₂, CCl₂=CH). In tetrachloroalkanes CCl₃CH₂(CH₂)_nCl (n = 1, 3, 5) under the same conditions the selectivity of the CCl₃ and CH₂Cl groups relative to the nucleophile RCO₂K(Na) is altered — unsaturated esters RCO₂(CH₂)_nCH=CCl₂ are formed in one stage with yields of 75–90%. Under the selected conditions, high conversion of polychloroalkanes to esters is attained 3 to 5 times more rapidly than in acid media. The structure of the ester obtained has been confirmed by their PMR spectra.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2790–2793, December, 1990.     

Temperature and ionic strength influence on U(VI/V) and U(IV/III) redox potentials in aqueous acidic and carbonate solutions

Redox potentials: E(UO ₂ ²⁺ /UO ₂ ⁺ )=60±4 mV/NHE, E(U⁴⁺/U³⁺)=–630±4mV/NHE measured at 25°C in acidic medium (HClO₄ 1M) using cyclic voltametry are in accordance with the published data. From 5°C to 55°C the variations of the potentials of these systems (measured against Ag/AgCl electrode) are linear. The entropies are then constant: [S(UO ₂ ²⁺ /UO ₂ ⁺ )–S(Ag/AgCl)]/F=0±0.3 mV/°C, [S(U⁴⁺/U³⁺)–S(Ag/AgCl)]/F=1.5±0.3 mV/°C. From 5°C to 55°C, in carbonate medium (Na₂CO₃=0.2M), the Specific Ionic Interaction Theory can model the experimental results up to I=2M (Na⁺, ClO ₄ ^– , CO ₃ ^2– ): E(UO₂(CO₃) ₃ ^4– /UO₂(CO₃) ₃ ^5– )=–778±5 mv/NHE (I=0, T=25°C, (25°C)=(UO₂(CO₃) ₃ ^4– , Na⁺)–(UO₂(CO₃) ₃ ^5– , Na⁺)=0.92 kg/mole, S(UO₂(CO₃) ₃ ^4– /UO₂(CO₃) ₃ ^5– =–1.8±0.5 mV/°C (I=0), =(Cl^–, Na⁺)=(1.14–0.007T) kg/mole. The U(VI/V) potential shift, between carbonate and acidic media, is used to calculate (at I=0,25°C):

High-Temperature Oxidation of Methane by Supported Lead Oxide

The kinetics of the reduction of PbO supported on Al₂O₃by methane is studied in the temperature range 760–927°C. The reaction order with respect to methane is equal to unity and the apparent activation energy is 40 kcal/mol. When the extent of PbO reduction is 0.5–0.6, the selectivity of methane conversion changes drastically: only CO₂is formed at lower extents of reduction, whereas CO is the main product at higher extents.     

Oxidation of propene in the gas phase

A series of laboratory and modelling experiments on the oxidation of propene in the gas phase has been undertaken to determine conditions which give high yields of propene oxide. The conditions under which the experiments were conducted were 505–549 K and up to 4 bar pressure. It is proposed that propene oxide is formed from propene by reaction with several peroxy radicals including HO₂ and CH₃CO₃. However, one of the more important radicals is hydroxypropylperoxy. Its reaction with propene, under these conditions is more important than concerted decomposition to formaldehyde and acetaldehyde. © 1995 John Wiley & Sons, Inc.     

Kinetics of the Ru(III) catalyzed oxidation of formaldehyde and acetaldehyde by alkaline hexacyanoferrate(III)

The kinetics of ruthenium(III) catalyzed oxidation of formaldehyde and acetaldehyde by alkaline hexacyanoferrate(III) has been studied spectrophotometrically. The rate of oxidation of formaldehyde is directly proportional to [Fe(CN) _3– ⁶ ] while that of acetaldehyde is proportional tok[Fe(CN) _3– ⁶ ]/{k +k[Fe(CN) _3– ⁶ ]}, wherek, k andk are rate constants. The order of reaction in acetylaldehyde is unity while that in formaldehyde falls from 1 to 0. The rate of reaction is proportional to [Ru(III)] _T in each case. A suitable mechanism is proposed and discussed.

---

Die Kinetik der Ru(III)-katalysierten Oxidation von Formaldehyd und Acetaldehyd mittels alkalischem Hexacyanoferrat(III)

Zusammenfassung Die Untersuchung der Kinetik erfolgte spektrophotometrisch. Die Geschwindigkeitskonstante der Oxidation von Formaldehyd ist direkt proportional zu [Fe(CN) _3– ⁶ ], währenddessen die entsprechende Konstante für Acetaldehyd proportional zuk[Fe(CN) _3– ⁶ ]/{k +k[Fe(CN) _3– ⁶ ]} ist, wobeik,k undk Geschwindigkeitskonstanten sind. Die Reaktionsordnung für Acetaldehyd ist eine erste, die für Formaldehyd fällt von erster bis zu nullter Ordnung. Die Geschwindigkeitskonstante ist in jedem Fall proportional zu [Ru(III)] _T . Es wird ein passender Mechanismus vorgeschlagen.

     

Effect of the chemical nature of the support on the properties of platinum catalysts for the combined oxidation of CO and H2

The steady-state rate of hydrogen oxidation catalyzed by platinum on an inert support (corundum) is greater than the rate of oxidation of carbon monoxide, while the rate of hydrogen oxidation on a platinum-vanadium catalyst is less than the rate of oxidation of carbon monoxide. The conditions for the complete selective oxidation of the reaction mixture components were determined. Hydrogen is oxidized on the Pt/corundum cataljst at 273K in a non-steady-state mode, while CO is oxidized on the same catalyst at 273 K and on Pt/BaSO₄-V₂O₅ at 383–393K in a steady-state mode.Deceased.Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 31, No. 2, pp. 81–85, March–April, 1995.     

Isotopic analysis of243Cm and244Cm by internal conversion electron spectrometry

The electrodeposition of uranium and trace quantities of²³⁹Pu,²³⁴Th,¹⁴⁴Ce on a stainless steel disk has been investigated from 0.5–2.0M NaOH and the two-phase system: extract of actinides in TBP-aqueous solution of NaOH. The electrodeposition yield of the above elements reaches 98–100% in 40 min of electrolysis with current density 0.4–0.5 A/cm². The presence of 0.5M Na₂CO₃, 2.0M NaNO₃, 2.0M NaNO₂, 0.2M NaF in alkaline solutions does not decrease the electrodeposition yield. The electrodeposited films meet all the requirements of -spectrometry. The uranium oxidation states (V) and (IV) have been determined in the electrodeposited films.     

Transformations of formaldehyde and glycolaldehyde during the hydroformylation of formaldehyde in the presence of rhodium catalysts

Hydroformylation of formaldehyde to give glycolaldehyde (GA) in the presence of RhCl(PPh₃)₃, RhCl(CO)(PPh₃)₂, or the RhCl₃ + PPh₃ system inN,N-dimethylacetamide was studied. The hydroformylation is accompanied by the Cannizzaro-Tishchenko reaction, condensation of CH₂O with GA to give C₃-C₁₆ polyoxyaldehydes (POA), and dimerization of GA. The formation of POA, which probably occurs through coordination of GA with a Rh atom, predominates among the side reactions. The optimum conditions for hydroformylation of CH₂O were found to be: RhCl₃ + PPh₃ as the catalyst,T 383 K, 12MPa, [H₂O] 1.8 mol L^–1, [Rh] 2.5 · 10^–3 g-at. L^–1, and [CH₂O] 0.03 g L^–1. At a substrate conversion of 62–67 %, the selectivity of GA formation reaches 96 %, and the yield is 60–65 %.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 75–78, January, 1995.     

Study of the influence of alkali element compounds on the activity of aluminopalladium catalysts for oxidation of carbon monoxide

A discussion is presented of a discovery that the anionic part of sodium salts introduced into the catalyst by impregnation of -Al₂O₃ after deposition of palladium salts and their reduction in that catalyst affects the activity and dynamic properties of the catalysts in the oxidation reaction of CO into CO₂ at stoichiometric ratios of CO/O₂ = 2.Scientific-Production Association Gos. In-t Prikl. Khim., Leningrad. Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 27, No. 5, pp. 591–595, September–October, 1991. Original article submitted July 17, 1991.     

Radiation-Chemical Oxidation of Molecules in the Lipid Bilayer of Lecithin Liposomes by Radiolytic Products Formed in the Radiolysis of an Aqueous Dispersion

The buildup of oxidation products of L--phosphatidylcholine, the constituent of liposome lipid bilayers, was studied depending on the qualitative and quantitative composition of radiolytic species formed on irradiation of an aqueous dispersion. The presence of ionol (2,6-di-tert-butyl-4-methylphenol) as a nonselective radical scavenger at a concentration of 2.5 × 10^–4 mol/g_lipid in a lipid bilayer decreased the accumulation of oxidation products by a factor of 3–7.     

Study of the carbonyl products of terpene/OH radical reactions: detection of the 2,4-DNPH derivatives by HPLC-MS

The oxidation of the terpenes - and -pinene, limonene and ³-carene by hydroxyl radicals has been investigated in a fast-flow reactor coupled to a liquid nitrogen trap for collecting the carbonyl compounds. Identification of the products was performed via 2,4-dinitrophenylhydrazone (DNPH) derivatization of the carbonyls to form the mono- and di-DNPH derivatives, which were analysed by high-performance liquid chromatographic (HPLC)-DAD (diode array detector) and HPLC-mass spectrometry (HPLC-MS). Both electrospray ionization [ESI(–)] and atmospheric pressure chemical ionization [APCI(–)] were suitable for the detection of the DNPH derivatives of formaldehyde, acetaldehyde, myrtanal, campholene aldehyde, perillaldehyde, acetone, nopinone, trans-4-hydroxynopinone and 4-acetyl-1-methylcyclohexene. Also the mono-DNPH derivatives of the dicarbonyl compounds pinonaldehyde, endolim and caronaldehyde could be identified. The MS² spectra generated in the ion trap of the mass spectrometer allowed us to distinguish between aldehydes and ketones on the basis of the characteristic fragment ion m/z 163 for the aldehydes. For the quantitative analysis of the mono-DNPH derivatives, ESI(–) in combination with single ion monitoring (SIM) detection showed the lowest detection limits. For the quantification of the dicarbonyl compounds, the acid-sensitive di-DNPH derivatives had to be formed by keeping the acidity in the acid-catalysed derivatization reaction at about 1.7 mM H₂SO₄. Detection of these dicarbonyl compounds can only be performed by APCI(–) with somewhat lesser sensitivity than by HPLC-DAD.