Photochemische Carbonylierung und Oxydation von wässerigem Methanol bei 1470 Å

Zusammenfassung Das photochemische Verhalten von wässerigem Methanol, gesättigt mit Argon, CO bzw. O₂ wurde bei 1470 Å als Funktion der VUV-Dosis und der Methanolkonzentration untersucht. Als Reaktionsprodukte wurden Wasserstoff, Formaldehyd, Glykolaldehyd, Glykol, Ameisensäure und in Gegenwart von Sauerstoff auch Peroxyd nachgewiesen. In 10^–2 m-Methanol, gesättigt mit Argon, betrug (H₂)=0,69 und (HCHO)=0,22, in Gegenwart von 7·10^–4 m-CO war (H₂)=0,10 und (HCHO)=0,29, während bei Sättigung mit O₂ (10^–3 mO₂) (H₂)=0,01, (HCHO)=0,33, (HCOOH)=0,20 und (H₂O₂)=0,22 gefunden wurde. Die -Werte der übrigen Produkte, die unter den angegebenen Bedingungen erhalten wurden, waren <0,07. Durch Erhöhung der Methanolkonzentration bis zu reinem Methanol, gesättigt mit Argon, stieg die Ausbeute von H₂, HCHO und (CH₂OH)₂ entsprechend an, während die von HCOOH und CH₂OHCHO sich praktisch nicht änderte. Bei reinem, mit Argon gesättigtem Methanol war (H₂)=0,89 und (HCHO)=0,73. Das Glykol erreichte bei etwa 2m-Methanol eine Höchstausbeute von =0,38. Reaktionsmechanismen werden diskutiert.

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Photochemical carbonylation and oxidation of aqueous methanol at 1470 Å

The photochemical behaviour of aqueous methanol saturated with argon, CO and O₂, resp., has been investigated at 1470 Å as a function of the v.u.v. dose and the methanol concentration. Hydrogen, formaldehyde, glycolaldehyde, glycol, formic acid and, in the presence of oxygen, also peroxide were detected. In 10^–2 M-CH₃OH saturated with argon (H₂)=0,69 and (HCHO)=0,22 were found; in the presence of 7·10^–4 M-CO the yields are (H₂)=0,10 and (HCHO)=0,29, whereas under saturation with oxygen (10^–3 M O₂) (H₂)=0,01, (HCHO)=0,33, (HCOOH)=0,20 and (H₂O₂)=0,22. The quantum yields of all other products obtained under the conditions mentioned above are <0.07. With increasing methanol concentration up to pure argon saturated methanol, the quantum yields of H₂, HCHO and (CH₂OH)₂ increase correspondingly, whereas the yields of HCOOH and CH₂OHCHO remain practically unchanged. When irradiating pure, argon saturated methanol, (H₂)=0,89 and (HCHO)=0,73 were found. A maximum yield of (CH₂OH)₂=0,38 was achieved using 2M-CH₃OH. Reaction mechanisms are discussed.

     

Isoparametric kinetic relations for chemical transformations in condensed substances (analytical survey). I

The compensation effect related to isoparametric correlations is analysed within the formal theory, and the statistical and physico-chemical aspects of these correlations are considered.

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Zusammenfassung Der sich auf isoparametrische Korrelationen beziehende Kompensationseffekt wird im Rahmen der formalen Theorie analysiert. Statistische und physikalisch-chemische Aspekte dieser Korrelationen werden erörtert.

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, - . - - .

     

Effect of metal ions forming bromide complexes on the Belousov-Zhabotinskii reaction

Metal ions forming stable complexes with bromide ions greatly influence both the amplitude and frequency of the Belousov-Zhabotinskii reaction. In case of thallium(I), redox reactions involving the metal ion should also be considered beside complex formation.

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, , , -. (I), , .

     

EXAFS Study of Ph3GeMn(CO)5 Structure Evolution on Exposure to X-Radiation

Ge K-edge and Mn K-edge EXAFS spectroscopy was used to study changes in the local environment of germanium and manganese atoms during radiolysis of the Ph₃GeMn(CO)₅ complex. On exposure to X-radiation, the metal complex undergoes a number of transformations depending on the radiant exposure (). It was shown that at = (6–8) × 10⁶ J/m², the initial metal complex decomposes into the [Ph₃Ge] and [Mn(CO) _n ] fragments with partial detachment of the CO groups from Mn atoms. When = 1.3 × 10⁷ J/m², Mn atoms lose completely the CO groups to form finely dispersed metal nanoparticles, which interact with the surrounding atoms (carbon or nitrogen). With further increase in , the local environment of the Mn atoms no longer changes. The Ge atoms remain coordinated to the Ph groups as increases up to 2 × 10⁷ J/m², but starting with = 1.6 × 10⁷ J/m², metal–metal bonds are formed; subsequently, the amount of this phase increases and when = 2.6 × 10⁸ J/m², it becomes predominant. Since manganese and germanium atoms lose their ligands at different values, one can conclude that germanium and manganese nanoparticles are the final products in the radiolysis of Ph₃GeMn(CO)₅.     

Anwendung thermometrischer Methoden auf die Untersuchung von oxydationsmechanismen aromatischer Amine

Zusammenfassung An Hand von Oxydationsreaktionen einiger aromatischer Amine, deren mechanismus bekannt ist, wurde gezeigt, daß enthalpiometrische Titrationskurven in bedeutenden mass zur Formulierung des Reaktionsmechanismus beitragen und auf diese Weise eine wichtige Ergänzung der spektrophotometrischen, potentiometrischen, chromatographischen und weiteren Methoden bilden. In einigen Fällen ist deren Gebrauch unersetzbar.

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In the oxidation reactions of some aromatic amines with known mechanisms, it was shown that the enthalpimetric titration curves could provide considerable help in the determination of the mechanisms, acting as an important complement for spectrophotometry, potentiometry, chromatography and other methods. In some cases the method proved irreplaceable.

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, , , , , . .

     

51V-NMR spectra of vanadates and oxosulfato-vanadates of alkali metals

A relation between the type of vanadium environment and the chemical shift anisotropy in the⁵¹V-NMR spectra has been established. The results obtained are compared with spectra of real catalysts.

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⁵¹V , .

     

Investigation of complete oxidation of organic materials with thermal analytical measurements

The complete oxidation of styrene-divinylbenzene has been examined with complex thermoanalytical methods by derivatograph and thermogastitrimeter. With the combined application of combustion catalyst and postcatalytic method the oxidation of the styrene-divinylbenzene is complete.

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Zusammenfassung Die vollständige Oxydation von Styrol-Divinylbenzol wurde mittels einer komplexen thermoanalytischen Methode unter Verwendung eines mit einem Gastitrimeter kombinierten Derivatographen untersucht. Eine vollständige Oxydation wird bei Anwendung eines Verbrennungskatalysators und der postkatalytischen Methode erreicht.

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- . .

     

3, 3, 3-Trifluoropropyl(methyl)cyclosiloxanes

The catalytic rearrangement of the cyclopentasiloxanes _mD_5-m, where represents a 3, 3, 3-trifluoropropyl(methyl)siloxane link and D a dimethylsiloxane link, and m=2–5 has been studied by the method described previously [1]. The rate of rearrangement and the rate of formation of a linear polysiloxane rise with an increase in m from 2 to 4. The equilibrium concentration of the linear polysiloxane formed from _mD_5-m and from _mD_4-m (m=0–4) [1] is inversely proportional to the molar fraction of links in the ring and rises with an increase in the total concentration of siloxane links in solution. Results have been obtained on the kinetics of the formation of the cyclosiloxanes _mD_n (where m=0–5, n=0–5, and m+n=3-6) during the rearrangement of the cyclopentasiloxanes _mD_5-m. It has been established that at equilibrium a mixture of cyclosiloxanes _mD_n containing practically constant ratios of tetramers, pentamers, and hexamers (m+n=4, 5, and 6) is obtained, regardless of the composition and structure of the initial cyclosiloxane and of the conditions of rearrangement (polymerization). The cyclopentasiloxanes _mD_5-m are less active in the process of rearrangement than the cyclotetrasiloxanes _mD_4-m. The activity of the cyclosiloxanes in rearrangement in the presence of a base rises in the sequence D₄D_{3 2}D₃<₃D₂<₄D < ₂D₂ < ₃D.For part II, see [1].     

The Influence of Dimerization of Water-Soluble Metalloporphyrins as Photosensitizers on the Efficiency of Generation of Singlet Oxygen

Quantum yields () for the generation of singlet oxygen sensitized by Pd(II) complexes of water-soluble porphyrins: meso-tetrakis(4-N-methylpyridyl)porphine [PdTMPyP]⁴⁺ ( = 0.9), meso-tetrakis(4-N,N,N-trimethylaminophenyl)porphine [PdTTMAPP]⁴⁺ ( = 0.8), meso-tetrakis(4-carboxyphenyl)porphine [PdTCPP]^4– ( = 0.7), and meso-tetrakis(4-sulfonatophenyl)porphine [PdTSPP]^4– ( = 0.5) were determined using a chemical method. It was found that the dimerization and aggregation of metalloporphyrins greatly influence the value. The quantum yields evaluated for the formation of singlet oxygen sensitized by metalloporphyrin monomeric and dimeric forms are _{, M} 0.9 and _{, D} 0.2, respectively, and do not depend on the porphyrin nature.     

Seawater—A test of multicomponent electrolyte solution theories. I. The apparent equivalent volume,expansibility, and compressibility of artificial seawater

The apparent equivalent volume _V, expansibility _E, and compressibility _K of an artificial seawater solution containing10 ionic components (Na⁺, Mg²⁺, Ca²⁺, K⁺, Sr²⁺, Cl^–, SO ₄ ^2– , HCO ₃ ^– , Br^–, and F^–) and one nonionic component (H₃BO₃) has been determined from0 to40°C (in5° intervals) and from0.1 to0.8 m ionic strength at1 atm. The concentration dependence (I_v=volume ionic strength) of the _V's, _E's, and _K's have been examined by using a Masson-type equation, = ^° +S'I _V ^1/2, and a Redlich-type equation, = ^° +SI _V ^1/2 +BI _V, where ^° is the infinite-dilution value, S is the empirical Masson slope, S is the theoretical Debye-Hückel slope, and B is an empirical deviation constant. By using Young's rule, = E_i(i), the apparent equivalent volumes, expansibilities, and compressibilities for sea salt have been estimated from the ionic and nonionic components making up the mixture. The estimated apparent molal quantities agree very well with the directly measured values providing the concentration terms, S _i and B_i, are weighted according to the methods of Wood and Reilly.Contribution Number 1599 from the University of Miami.     

Partial molal expansibilities of organic compounds in aqueous solution. I. Alcohols and ethers

The temperature dependence of limiting apparent molal volumes ° in water for some alcohols (methanol, ethanol, 1-propanol, 2-butanol, 3-pentanol, 3-hexanol, 2,5-hexanediol, cyclopentanol, cyclohexanol, cycloheptanol, and 1,4-cyclohexanediol) and ethers (trimethylene oxide, tetrahydrofuran, tetrahydropyran, 1,3-dioxolane, 1,3-dioxane, 1,4-dioxane, 1,3-dioxepane, 1,3,5-trioxane, dimethoxymethane, 1,2-dimethoxyethane, diethoxymethane, and diethyl ether) has been studied in the temperature range 10–50°C by means of an automatic digital-readout dilatometer. Values of the thermal expansion coefficient * = (1/°)(°/T)_p have been obtained at several temperatures and discussed together with literature data on expansibilities of related compounds. The data show a wide spectrum of values of ^* at low temperatures which is narrowed at the higher ones. The expansibilities of monofunctional alcohols increase with increasing temperature; the opposite effect is observed for polyhydric alcohols. The ^*'s of ethers are very slightly temperature dependent and are much higher, at low temperature, than those of alcohols having the same ratio ofn _o/n_c. These results are discussed in terms of solutewater interactions, and a possible interpretation is put forward.     

X-ray diffraction studies of mercury structure and properties in pores of disperse matrices

X-ray diffraction studies of the samples obtained by mercury embedding into pores of disperse matrices have been carried out at T=303–83 K. It has been established that in this case the melting temperature of disperse mercury decreases, its oxidation is activated and the cell parameters increase.

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303–83 K , . , , .

     

Heterogeneous reactions of solid nickel(II) complexes,XI

The influence of factors caused by different experimental conditions on the stoichiometry of thermal decomposition of the complex Ni(NCS)₂(-picoline)₄ was studied. By means of TG it was found that the release of-picoline was shown by the derivatograph (air atmosphere, sample of 50–500 mg, rate of temperature increase 1–6°/min, crucible with a hole in the bottom) in three steps (–2, –1, –1), by the micro-balance (sample of 2.59 mg) in two steps (–2, –2), and by the vacuum thermobalance in one step (–4). Under quasi-isothermal and quasi isobaric conditions in a special crucible-picoline was released in three steps (–1, –2, –1). An analogous result was obtained with the derivatograph using a crucible with a lid. The reasons for these differences are discussed.

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Zusammenfassung Der Einfluß verschiedener Versuchsbedingungen auf die Stöchiometrie der thermischen Zersetzung des Komplexes Ni(NCS)₂(-Pikolin)₄ wurde untersucht. Mittels TG wurde festgestellt, daß der Derivatograph (Luft-Atmosphäre, 50–500 mg Probe, Geschwindigkeit des Temperaturanstiegs 1 bis 6 °C/min., Tiegel mit Loch im Boden) die Freisetzung des-Pikolins in drei Stufen (–2, –1, –1), die Mikrowaage (Probe von 2.59 mg) in zwei Stufen (–2, –2) und die Vakuumthermowaage in einer Stufe (–4) angibt. Bei quasi-isothermen und quasi-isobaren Bedingungen in einem besonderen Tiegel wurdeß-Pikolin in drei Stufen (–1, –2, – 1) freigesetzt. Ein ähnliches Ergebnis wurde mit dem Derivatograph en bei Verwendung eines Tiegels mit Deckel erhalten. Die Ursachen dieser Unterschiede werden erörtert.

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Résumé On a étudié l'influence des facteurs en relation avec des conditions d'expérience différentes, sur la stoechiométrie de la décomposition thermique du complexe Ni(SCN)₂ (-picoline)₄. On a établi que le dégagement de la-picoline s'effectue en trois étapes (–2, –1, –1) si l'expérience TG est réalisée à l'aide d'un Derivatograph (atmosphère d'air, échantillon de 50–500 mg, vitesse d'échauffement 1–6 °C/min, creuset avec fond percé d'un trou), en deux étapes (–2, –2) avec une microbalance (prélèvement de 2.59 mg) et en une étape (–4) si l'expérience TG est réalisée sous vide. En conditions quasi-isothermes et quasi-isobares, dans un creuset de forme spéciale, la-picoline se dégage en trois étapes (–1, –2, –1). On parvient à un résultat analogue avec un Derivatograph en utilisant un creuset muni d'un couvercle. On discute les causes de ces différences.

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, , Ni(NCS)₂ ( )₄. , ( , 50–500 , 1–6 °/, ) (–2, –1, –1), ( 2.59 ) — (–2, –2) - — (–4). - - (–1, –2, –1). , . .

     

Apparent molar volumes of aqueous calcium chloride to 250°C, 400 bars,and from molalities of 0.242 to 6.150

Relative densities of CaCl ₂ (aq) with 0.22ml(mol-kg^–1)6.150 were measured with vibrating- tube densimeters between 25 and 250°C and near 70 and 400 bars. Apparent molar volumes V calculated from the measured density differences were represented with the Pitzer ioninteraction treatment, with appropriate expressions chosen for the temperature and pressure dependence of the virial coefficients of the model. It was found that the partial molar volume at infinite dilution V ^o , and the second and third virial coefficients B ^V and C ^V , were necessary to represent V near the estimated experimental uncertainty. The ionic-strength dependent ^(1)v term in the B ^V coefficient was included in the fit. The representation for V has been integrated with respect to pressure to establish the pressure dependence of excess free energies over the temperature range studied. The volumetric data indicate that the logarithm of the mean ionic activity coefficient, ln ±(CaCl ₂ ), increases by a maximum of 0.3 at 400 bars, 250°C, and 6 mol-kg^–1 as compared with its value at saturation pressure.     

Studies of the reactions of Br(2P3/2) and Br(2P1/2) with SiH4

Photobromination of SiH₄ under uv-irradiation at various wavelengths has been studied. Rate constants for the elementary reactions Br(²P_3/2)+SiH₄HBr+SiH₃ (k=3.2×10^–11 exp(–21.8±2.5)/RT, cm³/s) and Br^* (²P_1/2)+SiH₄HBr+SiH₃ (k^*=(3±1)×10^–13 cm³/s) have been determined in the temperature range from 300 to 415 K.

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- . Br(²P_3/2)+SiH₄HBr+SiH₃, k=3,2×10^–11 exp (–21,8±2,5)/RT ³/ Br^*(²P_1/2)+SiH₄HBr+SiH₃, k^*=(3±1)×10^{–13 3}/ 300–415 K.

     

On a variational method for determining excited state wave functions

A variational method is proposed which results in an approximate wave function for an excited state which has the maximum overlap with the true excited state eigenfunction. The method involves the calculation of the quantities E=¦H¦ and =¦(H-E)²¦, but is free of the constraint that the trial function must remain orthogonal to all states of the same symmetry which lie beneath it. One must know, however, an approximation to the true eigenvalue. A discussion is given on how one might gain the latter information, lacking knowledge of the spectrum, from the repeated application of the method.

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Zusammenfassung Es wird eine Variationsmethode vorgeschlagen, die auf eins genäherte Wellenfunktion für einen angeregten Zustand führt, welche sich maximal mit der wahren Eigenfunktion des angeregten Zustandes überlappt. Die Methode ermöglicht die Berechnung der Größen: E=¦H¦ und =¦(H-E)²¦, ist aber frei von der Nebenbedingung, daß die Versuchsfunktion orthogonal zu allen benachbarten Zuständen mit derselben Symmetrie bleiben muß. — Man will jedoch eine Näherung des wahren Eigenwertes wissen. — Eine Diskussion darüber, wie man durch wiederholte Anwendung der Methode letztere Information gewinnen kann, ohne Kenntnisse über das Spektrum zu besitzen, wird durchgeführt.

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Résumé Méthode variationnelle pour la détermination d'une fonction d'onde d'un état excité présentant le recouvrement maximum avec la fonction d'onde exacte. La méthode implique le calcul de E=¦H¦ et =¦(H-E)²¦ mais ne comporte pas la contrainte d'orthogonalité de la fonction d'essai à tous les états inférieurs de même symétrie. On doit cependant connaître une valeur approchée de la valeur propre exacte. Discussion sur la manière dont on peut obtenir cette valeur approchée sans connaître le spectre, par application répétée de la méthode.

     

Titration of reduced Al2O3 carrier by ferric chloride solution

It has been shown that alumina (or impurities in it) can be reduced under circumstances which are applied in the pretreatment of Pt/Al₂O₃ catalysts.

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, ( ) , Pt/Al₂O₃.

     

First experiments on transmutation studies of129I and237Np using relativistic protons of 3.7 GeV

First experiments on the transmutation of long-lived¹²⁹I and²³⁷Np using relativistic protons of 3.7 GeV are described. Relativistic protons generate in extended Pb-targets substancial neutron fluences. These neutrons get moderated in paraffin and are used for transmutation as follows:¹²⁹I(n,)¹³⁰I and²³⁷Np(n,)²³⁸Np. The isotopes¹³⁰I (T _1/2-12.36 h) and²³⁸Np (T _1/2=2.117 d) were identified radiochemically. One can estimate the transmutation cross-section (n,) in the given neutron field as (¹²⁹I(n,))=(10±2)b and (²³⁷Np(n,))=(140±30)b The experiments were carried out in November 1996 at the Synchrophasotron, LHE, Dubna, Russia. The investigation has been performed at the Laboratory of High Energies, JINR, Dubna.     

On the state of Re in the Pt/Re reforming catalysts

Both Pt/Al₂O₃ and (Pt+Re)/Al₂O₃ industrial catalysts contain, after reduction (at 450 °C) ions, extractable by acetylacetone. However, a substantial part of Re is reduced.

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Pt/Al₂O₃ (Pt+Re)/Al₂O₃ ( 450 °C) , . , .