Inductive hydrogen formation in the oxidation of ascorbic acid by nitrosylpentacyanoferrate(II)

In the first period of the reaction at pH 8 slow evolution of CO₂ and N₂O was observed. After gas evolution ceased, on adding NaOH, formation of N₂O again and, unexpectedly, H₂ was found. The amount of H₂ was measured as a function of reaction conditions. Illumination with visible light and the excess of the oxidant promote hydrogen evolution. The experiments in D₂O resulted in H₂, HD and D₂. The non-statistical isotope distribution was interpreted by a kinetic isotope effect.

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pH=8 CO₂ N₂O. NaOH, N₂O , , H₂. H₂ . . D₂O H₂, HD D₂. .

     

Basic properties of alkaline earth metal oxides and their catalytic activity in the decomposition of diacetone alcohol

The effect of CO₂ adsorption on the catalytic activity of alkaline earth metal oxides in the title reaction reveals that the number of active (basic) sites follows the order MgO>CaO>SrO>BaO, and the order of base strength is MgO

CO₂ , () : MgO>CaO>SrO>BaO, : MgO     

Role of tellurium in the oxidation of 1-butene on Te-doped CdMoO4

New active and selective catalysts were prepared by adding different quantities of Te to CdMoO₄. These were already selective at low Te levels, but the one with a Cd/Te/Mo ratio of 1/1/1 was specific for butadiene. The catalytic behavior of the Cd–Te–Mo–O system has been correlated mainly with the CdTeMoO₆ phase in the region rich in Te and with the CdMoO₄ phase with Te as dopant in the region poor in Te.

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Te CdMoO₄. Te, CdTeMo=111 . Cd–Te–Mo–O CdTeMoO₆ Te, CdMoO₄ Te , Te.

     

The Stevens rearrangement of methylenedimethyloxonium ylide: A quantum chemical study

The conversion of methylenedimethyloxonium ylide to ethyl methyl ether was investigated by the semiempirical MNDO method. An activation energy of 51 kJ/mol suggests that this rearrangement is a possible elementary reaction in the well-known MTG process.

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. 51 /, , .

     

Investigation of catalytic purification of gases from aromatic hydrocarbons

1,1- (AH) ([AH]=6,9 /, 50°C). AH W_i/W_{O 3}=0,40±0,16.

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The kinetics and oxidation products of 1,1-diethoxyethane (AH) ozonolysis have been investigated at [AH]=6.9 mol/l and 50 °C. The initiation efficiency of radical oxidation by ozone is W_i/W_{O 3}=0.40±0.16.

     

Thermal properties of the clathrate compounds of binary cyanides

The stoichiometry of thermal decomposition of a particular group of clathrate compounds, of the type Cd(en)Pd(CN)₄·2G, with the same coordination component but different clathrate-enclosed components, was investigated. Irrespective of the experimental conditions, the liberation of the enclosed component G always proceeded in one step. Thermal investigation of the decomposition stoichiometry under identical experimental conditions showed that the temperature intervals in which the enclosed components are given off shift to lower temperatures in the order C₆H₅OH=> C₆H₆ > > C₄H₅N > C₄H₄S. Diffraction measurements indicated a considerable change in the structures of the original clathrate compounds after thermal release of the enclosed componentG.

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Zusammenfassung Die Stöchiometrie der thermischen Zersetzung einer bestimmten Gruppe von Klathratverbindungen vom Typ Cd(en)Pd(CN)₄·2G mit der gleichen Koordinationskomponente und verschiedenen Klathrat-Einschlußkomponenten wurde in dieser Studie untersucht. Ungeachtet der Versuchsbedingungen vollzieht sich die Freisetzung der eingeschlossenen KomponenteG stets in einer Stufe. Die unter gleichen Versuchsbedingungen durchgeführte thermische Untersuchung der Zersetzungsstöchiometrie zeigte, daß die Temperaturbereiche, in denen die eingeschlossenen Komponenten freigesetzt werden in der Reihenfolge C₆H₅OH > C₆H₆ > C₄H₅N > C₄H₄S in Richtung der niedrigeren Temperaturwerte verschoben werden. Die Diffraktionsmessungen weisen darauf hin, daß eine beträchtliche Änderung der Struktur der ursprünglichen Klathratverbindung nach thermischer Freisetzung der eingeschlossenen KomponenteG sichtbar wird.

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Résumé Dans cette étude on a établi la stoechiométrie de la décomposition thermique d'un groupe particulier de clathrates du type Cd(en)Pd(CN)₄·2G, avec le même composant de coordination et différents composants occlus. Indépendamment des conditions d'expériences, la libération du composant occlusG s'effectue toujours en une étape. L'étude thermique de la stoechiométrie de la décomposition effectuée dans les mêmes conditions d'expériences, a montré que les intervalles des températures dans lesquels les composants occlus sont libérés, se déplacent vers les températures plus faibles dans l'ordre suivant: C₆H₅OH > C₆H₆ > > C₄H₅N > C₄H₄S. Les mesures de diffraction indiquent qu'après la libération thermique du composant occlusG, une variation considérable de la structure initiale des clathrates originaux apparaît.

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Cd(en)Pd(CN)₄. 2G . , G . , , , ] ₆₅>₆₆>C₄H₆N>C₄H₄S. - , G.

     

Mechanism of isotope exchange of dihydrogen with liquid ammonia catalyzed, by amide ions

The interacting bonds method (IBM) has been used for the analysis of hydrogen bonds in liquid ammonia, including estimates of the resonance components of the H=bonds of ammonia molecules with ammonium and amide ions. According to the E_a estimates for the interaction of a hydrogen molecule with an amide-ammonia solution (AAS) and the data on liquid ammonia structure, a kinetic mechanism for isotope exchange (IE) of hydrogen with liquid ammonia is formulated.

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(MBC) , -, - -. E_a - (AAP). () .

     

Modification of Fe species in FeNaY zeolite by NaCl treatment

The treatment of Fe(III)NaY zeolite with NaCl solution does not lead to a back-exchange of ferric species but the cationic Fe rearranges into new complexes which are more deeply reduced by hydrogen and less self-reduced by vacuum heat treatment than the parent Fe species in FeNaY zeolite.

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Fe(III)NaY NaCl . , Fe , , , Fe FeNaY.

     

A DSC-TLC analysis of thermolysis reactions involving 2'-deoxynucleosides

Differential scanning calorimetry (DSC) has provided a universal tool for ascertaining the effects of preparation and thermal history on the physical characteristics of polymers. When applied to the study of nonpolymeric compounds, however, the interpretation of thermal analysis data may be complicated by the possible occurrence of chemical as well as physical transformations under thermal stress. In the present study involving 2'-deoxynucleosides, this difficulty has been resolved by utilizing a DSC-TLC combination to correlate thermal phenomena with corresponding chemical and physical changes. This combination shows great promise in extending the application of DSC to the investigation of thermal reactions.

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Zusammenfassung Die Differential-Scanning-Kalorimetrie (DSC) ist besonders geeignet zum Nachweis des Einflusses der Herstellungsbedingungen und thermischen Vorgeschichte auf die Beschaffenheit von Polymeren. Beim Einsatz zur Untersuchung nicht-polymerer Verbindungen kann jedoch die Deutung der Daten der Thermoanalyse schwierig werden, da durch thermische Stresswirkung chemische sowie physikalische Unwandlungen stattfinden können. In diesem Beitrag, der sich mit 2'-Desoxynucleosiden befasst, wurde diese Schwierigkeit durch Anwendung einer Kombination von DSC und TLC behoben, welche die Korrelation thermischer Erscheinungen mit den entsprechenden chemischen und physikalischen Änderungen gestattete. Diese Kombination von DSC und TLC ist hinsichtlich der Erweiterung des Anwendungsgebiets der DSC auf die Untersuchung thermischer Reaktionen vielversprechend.

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Résumé L'analyse calorimétrique différentielle (DSC) est une méthode universelle pour mettre en évidence les effets de la préparation et du passé thermique sur les caractéristiques physiques des polymères. Cependant, si on l'applique à l'étude de composés non-polymères, l'interprétation des données d'analyse thermique peut être compliquée par l'intervention possible de transformations chimiques ou physiques sous l'effet du traitement thermique. Dans la présente étude sur les désoxy-2'-nucléosides cette difficulté est éliminée en combinant la DSC et la TLC afin d'établir une corrélation entre les phénomènes thermiques qui correspondent aux changements chimiques et physiques. L'emploi combiné de ces deux méthodes semble promis à une grande extension.

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. , , , . , 2- ** , - . ** .

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N.S.F. Undergraduate Research Participant from SUNY College at Plattsburg, Summer 1975.     

Silane-silanol condensation catalyzed by organotin compounds

The rate of condensation of H–SiR₂–(OSiR₂)_n–H (n=2, 3 or 4 and R=CH₃) and HO-SiRR–(OSiRR)₃–OH (R=C₆H₅) in xylene at 100 °C, catalyzed by dibutyltin diacetate, dilaurate and di-(2-ethyl)hexanoate, has been studied by infrared spectroscopy. The kinetic law is first order in each reactant and the reaction is accompanied by autocondensation of the silanol. The mecha nism involves complexation of the silanol with the catalyst, followed by the attack of a silane or silanol molecule.

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H–SiR₂–(OSiR₂)_n–H ( n=2,3 4 R=CH₃) HO–SiRR–(OSiRR)₃–OH ( R=C₆H₅) 100° C, , -(2-) , . . .

     

Binding energy of oxygen to the surface of promoted V?Mo?O catalysts for acrolein oxidation to acrylic acid

It has been established that P, Cs and Cu additives to V–Mo–O catalysts affect essentially both binding energy of surface oxygen and mobility of bulk oxygen.

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P, Cs Cu V–Mo–O .

     

Electronic state of the active site of A V?P?O/SiO2 catalyst in oxidation of chlorine-containing hydrocarbons

V⁴⁺ ions in slightly associated states are supposed to play the role of V–P–O/SiO₂ active sites. V⁴⁺ ions are reduced to V³⁺ during deactivation of the V–P–O/SiO₂ catalyst.

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V–P–O/SiO₂ V⁴⁺ . V–P–O/SiO₂ V⁴⁺ V³⁺.

     

Oxidative bromination of olefins catalyzed by thallium(III) and heteropolyacids in aqueous solutions

The system Tl^III+HPA-n, where HPA-n is the heteropolyacid H_3+nPMo_12–nV_nO₄₀ with n=2–8, in the presence of O₂ is found to be a homogeneous catalyst for the oxidative bromination of olefins by Br^– ions in aqueous solutions.

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, Tl^III+HPA-n, HPA-n — H_3+nPMo_12–nV_nO₄₀ n=2–8, O₂ Br^– .

     

Kinetics of the acid catalyzed hydrolysis of hydroxamic acids

The acid catalyzed hydrolysis of some alkylhydroxamic acids has been studied spectrophotometrically in perchloric, hydrochloric and sulfuric acids. Plots of the first order rate constant, k_obs against H⁺ show maxima, which are caused by protonation of the substrate. The mechanism of hydrolysis is found to be similar to that of amides. The variation of reaction rate with acid concentration can be described by a two-parameter equation.

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, , , . k_obs [H⁺] , . . .

     

Free-radical pyrolysis of ethanal in the presence of mono-or diolefins: Addition and hydrogen transfer mechanisms

The effects of mono-and diolefins on ethanal pyrolysis are summarized and discussed. It is shown that an addition and a hydrogen transfer mechanism, separately or together, may account for the experimental results obtained with various mono- and diolefins.

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- . , , , , - .

     

Routes of catalytic oxidation of o-xylene to phthalic anhydride

Relative reactivity of o-xylene, o-tolualdehyde, phthalide, and phthalane and the rate of phthalic anhydride formation from them have been determined. The main route of o-xylene oxidation to phthalic anhydride is due to the o-arrangement of methyl groups, proceeding through bicyclic products, such as dihydrobenzofuran (phthalane) and 3,4-benzofuran.

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-, - , , . - - : () 3,4-.

     

Studies of n-octane transformations on zeolites under hydrocracking conditions in a two-reactor flow-circulation system

Transformations of n-octane under hydrocracking conditions in a two-reactor flow-circulation system have been studied. It has been established that at high hydro-dehydrogenation activity of zeolite catalysts the reaction mechanism involves an initial step of paraffin dehydrogenation on a metal component and subsequent steps of cracking, isomerization and disproportionation of intermediate olefins on an acid component. Sodium content in zeolite determines the paraffin hydrocracking selectivity.

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- - . , - , . .

     

Effect of pretreatment in benzene hydrogenation on Pt/nylon catalyst

Benzene hydrogenation on Pt/nylon catalyst produced cyclohexene and cyclohexane, in contrast to Pt/SiO₂ on which only cyclohexane was detected. Higher selectivity to cyclohexene was found at higher temperature and after air pretreatment. It is suggested that an oxidized platinum species is responsible for cyclohexene formation.

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Pt/ , Pt/SiO₂, . . , .

     

ESR studies of photoinduced centers on weakly reduced anatase

The paramagnetic centers of reduced anatase (g₁=1.999, g₂=1.984, g₃=1.979) and (g₁=2.046, g₂=2.008), assigned to the stabilization of photoinduced holes near anion vacancies, have been studied. For the reduced oxide a new type of O₂ photoadsorption at h >1 eV due to the generation of only electron surface centers has been discovered.

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, : (g₁=1,999, g₂=1,984, g₃=1,979) (g₁=2,046, g₂=2,008), . O₂ h>1 , .

     

Hydrogen exchange in intramolecular cycloalkylation of phenylalkanols

Hydrogen exchange in intramolecular cycloalkylation of 2-methyl-4-phenyl-2-butanol (I) and 2-methyl-5-phenyl-2-pentanol (II) in the presence of 85% D₂SO₄ has been studied. The product 1,1-dimethylindane(III) is shown to contain deuterium in both aromatic ring and polymethylene fragment, whereas 1,1-dimethyltetralin (IV) contains deuterium only in the aromatic ring. A probable mechanism of the reaction is discussed.

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2--4--2- (I) 2--5--2- (II) 85% D₂SO₄. , 1,1- (III) , 1,1- (IV) . .