Naphthalene oxidation in supercritical water

Characteristic features of naphthalene oxidation and the kinetics of naphthalene pyrolysis in supercritical water (SCW) were studied using a batch reactor under isobaric conditions at a pressure of 30 MPa, in the temperature range from 660 °C to 750 °C, and for different levels of oxygen supply, varying from 0 to 2.5 moles of O₂ per mole of naphthalene. The pyrolysis produces benzene, toluene, methane, hydrogen, soot, and carbon oxides. The rate constant for naphthalene pyrolysis in SCW was found to be k = 10^12.3±0.2exp(–E/T) s^–1 where E = 35400±500 K. For T > 660 °C, water participates in the chemical reactions of naphthalene conversion, particularly, in the formation of carbon oxides. The conversion of naphthalene in pure SCW is accompanied by heat evolution. Molecular oxygen oxidizes a part of naphthalene completely, i.e., to CO₂ and H₂O, this reaction being so prompt that in some cases, self-heating of the mixture and thermal explosion in the reactor were observed.     

Heterocyclic analogs of pleiadiene

1-Methylperimidine adds phenylsodium and phenyllithium to the C=N bond to give 1-methyl-2-phenyl-2, 3-dihydroperimidines. However, if benzophenone is present in the reaction mixture, a mixture of 1-methyl-2-phenylperimidine and l-methyl-2, 4-diphenylperimidine (when phenylsodium is used) or l-methyl-2-phenyl-4-(-hydroxybenzhydryl)perimidine (when phenyllithium is used) is formed. It is assumed that the formation of products involving substitution in the naphthalene ring is associated with the participation of C₆H₅ and (C₆H₅)₂C-O^– radical particles that are formed on reaction of the phenylmetallic compound with benzophenone.See [1] for communication XXIII.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 697–701, May, 1976.     

Thermal isomerization of azulene to naphthalene in shock waves

The thermal isomerization of azulene was studied in shock waves over the range 1300–1900 K. Monitoring azulene and naphthalene light absorptions in the UV, a complete conversion azulene → naphthalene was observed. After correction for some falloff effects, a limiting high pressure rate constant k_x = 10^12.93 exp(?263 kJ mol^?1/RT) s^?1 was derived. Based on this k_x, specific rate constants k(E) for photoexcitation experiments were constructed.     

Diels—Alder reaction between naphthalene and N-phenylmaleimide under mild conditions

The rate and equilibrium constants for the Diels—Alder reactions between benzene or naphthalene and several dienophiles at 25 °C were calculated from the data on the ionization potentials of dienes and electron affinity energies of dienophiles, as well as the reaction enthalpies. The highest yield of the adduct was predicted for the reaction of naphthalene with N-phenylmaleimide. However, the time of its formation in 50% yield exceeds 30 years. The use of gallium chloride as a catalyst affords the endo-adduct for seven days at room temperature in 30% yield. The rate ((2±0.5)·10–6 L mol^–1 s^–1) and equilibrium constants (5±2 L mol^–1) of the reaction were determined.     

Isotachophoretic determination of stability constants of Ho and Y complexes with diethylenetriaminepentaacetic acid and 1,4,7,10-tetraazadodecane-N,N′,N″,N-tetraacetic acid

The method of capillary isotachophoresis with conductivity detection was applied for the determination of the physico-chemical characteristics (conditional stability constants log β′) of holmium and yttrium complexes with DTPA (diethylenetriaminepentaacetic acid) and DOTA (1,4,7,10-tetraazadodecane-N,N′,N″,N-tetraacetic acid). The log β′ determination is based on the linear relation between the stability constants of lanthanide–DTPA (lanthanide–DOTA) complexes and the reduction of the zone of the complex owing to the bleeding phenomena (liberating free metal ion). The stability constants calculated using this relationship are comparable with the literary data obtained by other methods for both holmium (log β′_Ho–DTPA=21.9, log β′_Ho–DOTA=24.5) and yttrium complexes (log β′_Y–DTPA=21.2, log β′_Y–DOTA=24.4). Capillary isotachophoresis was applied for the determination of the optimum composition of the reaction mixture (metal:ligand ratio) as well.     

Enthalpy and entropy changes for the intercalation of small molecules to DNA. I. Substituted naphthalene monoimides and naphthalene diimides

Calorimetric studies have been performed on the intercalation of a series of nitro and amino substituted naphthalene monoimide cations to calf thymus DNA. For comparison, we also included in the study the unsubstituted naphthalene diimide dication. All of the substituted naphthalene monoimides formed dimers at the concentrations used in the calorimetric titrations, and dimerization constants for these compounds were derived from spectroscopic studies and used in calculating the H _B ^o parameters from the calorimetric data. The dimerization constants increase in the order 3-NO₂MI=4-NO₂MI>3-NH₂MI>4-NH₂MI. For the unsubstituted naphthalene monoimide and 3-NO₂MI and 4-NO₂MI, the H _B ^o parameters are within experimental error equal to that found for the naphthalene diimide, i.e., –4.3 kcal-mol^–1. Thus, changes in entropy cause the K _B for the diimide to be 40 times larger than that for the monoimide. This observation is consistent with the current electrostatic theory for counterion binding to DNA: a dication should cause the release of more counterions than a monocation and produce a more positive S _B ^o . For the amino substituted naphthalene monoimides, the K _B values are similar to the other monoimides, but H _B ^o =–6.7 kcal-mol^–1. We propose that a hydrogen bond is responsible for the unusual enthalpy and entropy effects seen for 3-NH₂MI and 4-NH₂MI.     

Oxidative cleavage of α, β-unsaturated compounds by pentachlorohydroxoplatinate(IV) in alkaline medium

The kinetics of oxidation of α,β-unsaturated compounds by platinum(IV) in the presence of alkali {[OH⁻]= (1–9) × 10⁻³ mol dm⁻³} have been investigated over the 303–318 K temperature range . The rate of the reaction is dependent on the first power of the concentrations of substrates, oxidant, and alkali. The rate constant increases with an increase in ionic strength and also with increasing dielectric constant of the medium. The oxidation rates follow the order: –CN > –CONH₂ > –COO⁻. The values of the third order rate constant (k₃) for the oxidation of acrylonitrile, acrylamide and acrylate are 1.24, 0.826 and 0.628 mol⁻² dm⁶ s⁻¹ respectively, at 303 K. The oxidations of the substrates by PtCl₅(OH)²⁻ take place by an inner-sphere mechanism. Platinum(IV) is reduced to platinum(II) by the substrates in a one-step two-electron transfer process to give reaction products. The major reaction product, HCHO, is identified from the reaction mixture using i.r. spectrometry, n.m.r. and C, H, N analysis. A tentative reaction mechanism, leading to the formation of products, has been suggested. The activation parameters of the reaction have been evaluated.     

SCF calculations of aromatic hydrocarbons the variable β approximation

The transition energies and intensities of naphthalene, anthracene, phenanthrene, pyrene, and azulene are calculated with a variable modification of the Pariser-Parr-Pople method. In this procedure each is determined from the bond order after every iteration. The dependence of on bond order is given by = –0.51 p + A ₀ eV where A ₀ is –1.90 eV (naphthalene and azulene), –1.84 eV (anthracene and phenanthrene), and –1.82 eV (pyrene). Precise knowledge of the molecular geometry is not required and the results are in good agreement with experiment.

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Zusammenfassung Die elektronischen Anregungsenergien sowie die zugehörigen Intensitäten von Naphthalin, Anthrazen, Phenantren, Pyren und Azulen wurden mit der Modifikation der variablen der Pariser-Parr-Pople Methode berechnet, bei welcher die -Werte nach jedem Iterationsschritt als Funktion der Bindungsordnung neu berechnet werden. Ihre Abhängigkeit ist durch = –0,51 p + A ₀ eV gegeben, wobei A ₀ –1,90 (Naphthalin und Azulen), –1,84 (Anthrazen und Phenantren) bzw. –1,82 (Pyren) ist. Für das Verfahren ist die genaue Kenntnis der Geometrie des Moleküls nicht vonnöten und die Resultate befinden sich in guter Übereinstimmung mit dem Experiment.

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Résumé Nous avons calculé les énergies et intensités des transitions électroniques de naphthalène, Anthracène, phénanthrène, pyrène et azulène par une méthode PPP modifiée, où les sont déterminés des indices de liaison p après chaque itération: = –0,51 p + A ₀ eV, où A ₀ = –1,90 (pour naphthalène et azulène), –1,84 (anthracène et phénanthrène) et –1,82 (pyrène), respectivement. On n'a pas besoin des géometries exactes des molécules. Les résultats s'accordent bien à l'expérience.

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Supported by the U.S. Atomic Energy Commission and National Science Foundation.     

Mechanistic aspects of the reduction of ruthenium(III) catalyzed

The kinetics of Ru_III catalyzed reduction of hexacyanoferrate(III) [Fe(CN)₆]^3–, by atenolol in alkaline medium at constant ionic strength (0.80 mol dm^–3) has been studied spectrophotometrically, using a rapid kinetic accessory. The reaction between atenolol and [Fe(CN)₆]^3– in alkaline medium exhibits 1:2 stoichiometry [atenolol:Fe(CN)₆ ^3–]. The reaction showed first order kinetics in [Fe(CN)₆]^3– concentration and apparent less than unit order dependence, each in atenolol and alkali concentrations. Effect of added products, ionic strength and dielectric constant of the reaction medium have been investigated. A retarding effect was observed by one of the products i.e., hexacyanoferrate(II). The main products were identified by i.r., n.m.r., fluorimetric and mass spectral studies. A mechanism involving the formation of a complex between the atenolol and the hydroxylated species of ruthenium(III) has been proposed. The active species of oxidant and catalyst were [Fe(CN)₆]^3–and [Ru (H₂O)₅OH]²⁺, respectively. The reaction constants involved in the mechanism were evaluated. The activation parameters were computed with respect to the slow step of the mechanism, and discussed.     

Reaction of Germanium Tetrachloride with Chloro(phenyl)silanes in the Presence of Aluminum Chloride

The effect of the quantity of aluminum chloride on the direction and depth of reaction of germanium tetrachloride with chloro(phenyl)silanes of the general formula Ph_nSiCl_4−n (n = 1 – 3) was studied to show that radical exchange between germanium and silicon is initiated only if the mixture contains no less than 2.5–5 wt % of aluminum chloride. With trichloro(phenyl)silane, the radical exchange is initiated at 5 wt % of aluminum chloride and results in exclusive formation of trichloro(phenyl)germane. The reactions of GeCl₄ with dichlorodiphenylsilane and chlorotriphenylsilane in the presence of 2.5–7.5 wt % of aluminum chloride give dichlorodiphenylgermane as the major product, and at AlCl₃ concentrations of above 10 wt % the major product becomes to be trichloro(phenyl)germane.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 6, 2005, pp. 920–922.Original Russian Text Copyright © 2005 by Zhun’, Sbitneva, Chernyshev.     

Functionalization of saturated hydrocarbons

Alkanes and cycloalkanes (isobutane, butane, isopentane, isohexane, and methylcyclopentane) react with benzene or bromobenzene at 0–20 °C in the presence of RCO⁺Al₂X₇ ^– complexes (R=Me, Pr, or Ph; X=Cl or Br) to give products of the alkylacylation of arenes. The yields of alkylated aromatic ketones reach 60–87 % in 5–30 min, whereas the yields of unalkylated aromatic ketones (the competitive reaction) reach 0–40 %. The reactions of isobutane or isopentane with benzene result exclusively inpara isomers oft-BuC₆H₄COR or a mixture of Me₂(Et)CC₆H₄COR and Me(i-Pr)CHC₆H₄COR isomers (11), respectively. The reaction of isobutane with benzene also proceeds regioselectively and gives only one isomer, 2-Br-t-BuC₆H₄COR.For Part 2 seeIzv. Akad. Nauk, Ser. Khim., 1991, No 1, 105 [Bull. Acad. Sci. USSR. Div. Chem. Sci., 1991, No 1, 90 (Engl. Transl)].Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1253–1257, July, 1993.The authors express their gratitude to B. I. Bakhmutov for his assistance in interpreting the spectra.     

Pulse radiolysis studies on [Fe(CN)6]4−−BrO 3 − −CN− system in ethylene glycol — Water solutions

Formation of oxidizing and reducing radicals has been studied by pulse radiolysis of [Fe(CN)₆]^4––BrO ₃ ^– –CN^– system in ethylene glycol — water solvent mixture. Oxidizing ·BrO₂ and BrO radicals formed by electron scavenging with ·BrO ₃ ^– were identified and their reactions were investigated. The reaction of hydroxyl radicals with ethylene glycol leads to formation of reactive radicals with reducing properties and of compounds which reduce slowly in dark the ferricyanide formed in the reaction of ·BrO₂ radical with ferrocyanide.     

Formation of 6,10‐Diphenyl‐Substituted Heptalene‐4,5‐dicarboxylates

It is shown that 4,8‐diphenylazulene ( 1 ) can be easily prepared from azulene by two consecutive phenylation reactions with PhLi, followed by dehydrogenation with chloranil. Similarly, a Me group can subsequently be introduced with MeLi at C(6) of 1 (Scheme 2). This methylation led not only to the expected main product, azulene 2 , but also to small amounts of product 3 , the structure of which has been determined by X‐ray crystal‐structure analysis (cf. Fig. 1). As expected, the latter product reacts with chloranil at 40° in Et₂O to give 2 in quantitative yields. Vilsmeier formylation of 1 and 2 led to the formation of the corresponding azulene‐1‐carbaldehydes 4 and 5 . Reduction of 4 and 5 with NaBH₄/BF₃ ? OEt₂ in diglyme/Et₂O 1 : 1 and BF₃ ? OEt₂, gave the 1‐methylazulenes 6 and 7 , respectively. In the same way was azulene 9 available from 6 via Vilsmeier formylation, followed by reduction of azulene‐1‐carbaldehyde 8 (Scheme 3). The thermal reactions of azulenes 1, 6 , and 7 with excess dimethyl acetylenedicarboxylate (ADM) in MeCN at 100° during 72 h afforded the corresponding heptalene‐4,5‐dicarboxylates 11, 12 , and 13 , respectively (Scheme 4). On the other hand, the highly substituted azulene 9 gave hardly any heptalene‐4,5‐dicarboxylate.     

The Mechanism of Selective NO<Subscript>x</Subscript> Reduction by Hydrocarbons in Excess Oxygen on Oxide Catalysts: III. Adsorption Properties of the Commercial STK Catalyst

According to X-ray diffraction data, the STK catalyst is a mixture of Fe₂O₃ and Cr₂O₃. The temperature-programmed reduction spectrum exhibited two reduction peaks: one, with T _max = 250°C, corresponds to the reduction process Cr₂O₃ → CrO and the other, with T _max = 360°C, corresponds to the reduction Fe₂O₃ → Fe₃O₄. The results of thermal desorption measurements suggest that the individual adsorption of oxygen on the surface of the STK catalyst is low; in this case (according to IR-spectroscopic data), an atomic form is the main species. Surface nitrite-nitrate complexes are formed upon the adsorption of NO. Nitrite and nitrate complexes desorbed at maximum rates at 105 and 160°C, respectively. Unlike the NTK-10-1 catalyst, the NO species, which desorbed at high temperatures (250–400°C), was absent from the surface of STK. Propane adsorbed at room temperature to form surface compounds containing an acetate group. The interaction of propane with the surface of the STK catalyst at reaction temperatures resulted in strong surface reduction.__________Translated from Kinetika i Kataliz, Vol. 46, No. 4, 2005, pp. 550–558.Original Russian Text Copyright © 2005 by Tret’yakov, Burdeinaya, Zakorchevnaya, Matyshak, Korchak.     

Metal carbonyl catalysis of carbon monoxide and formate reactions

The water gas shift reaction (CO + H₂O = CO₂+ H₂) is catalyzed by aqueous metal carbonyl systems derived from simple mononuclear carbonyls such as Fe(CO)₅ and M(CO)₆ (M = Cr, Mo, and W) and bases in the 140–200 °C temperature range. The water gas shift reaction in a basic methanol-water solution containing Fe(CO)₅ is first order in [Fe(CO)₅], zero order in [CO], and essentially independent of base concentration and appears to involve an associative mechanism with a metallocarboxylate intermediate [(CO)₄Fe-CO₂H]^–. The water gas shift reactions using M(CO)₆ as catalyst precursors are first order in [M(CO)₆], inverse first order in [CO], and first order in [HCO₂ ^–] and appear to involve a dissociative mechanism with formatometallate intermediates [(CO)₅M-OCHO]^–.The Reppe hydroformylation of ethylene to produce propionaldehyde and 1-propanol in basic solutions containing Fe(CO)₅ occurs at 110–140 °C. This reaction is second order in [Fe(CO)₅], first order in [C₂H₄] up to a saturation pressure >1.5 MPa, and inhibited by [CO]. These experimental results suggest a mechanism where the rate-determining step involves a binuclear iron carbonyl intermediate. The substitution of Et₃N for NaOH as the base facilitates the reduction of propionaldehyde to 1-propanol but results in a slower rate for the overall reaction.The homogeneous photocatalytic decomposition of the formate ion to H₂ and CO₂ in the presence of Cr(CO)₆ appears to be closely related to the water gas shift reaction. The rate of H₂ production from the formate ion exhibits saturation kinetics in the formate ion and is inhibited by added pyridine. The infrared spectra of the catalyst solutions indicate an LCr(CO)₅ intermediate. Photolysis of the Cr(CO)₆/formate system in aqueous methanol in the presence of an aldehyde RCHO (R =n-heptyl,p-tolyl, andp-anisyl) results in catalytic hydrogenation of the aldehyde to the corresponding alcohol RCH₂OH by the formate ion. Detailed kinetic studies onp-tolualdehyde hydrogenation by this method indicates saturation kinetics in formate ion, autoinhibition by thep-tolualdehyde, and a threshold effect for Cr(CO)₆ at concentrations >0.004 mol L^–1. The presence of an aldehyde can interrupt the water gas shift catalytic cycle by interception of an HCr(CO)₅ ^– intermediate by the aldehyde.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1533–1539, September, 1994.     

Heterometallic Alkoxide Complexes of Variable Composition—A New Way to Ultrafine Powders of Metal Alloys

The anodic oxidation of Re metal in MeOH (Me = CH₃) provides a mixture of Re₂O₃(OMe)₆ and Re(V) oxoalkoxides that on storage or on heating give insoluble and air stable Re₄O_6–y (OMe)_12+y (I). I can be also obtained by reaction of Re₂O₇ with MeOH. In the presence of MoO(OMe)₄, a heterometallic complex ReMoO₂(OMe)₇(II) is formed as intermediate, the final product being Re_4–x Mo _x O_6–y (OMe)_12+y (III). The electrosynthesis in the presence of WO(OMe)₄ gives Re_4–x W _x O_6–y (OMe)_12+y (IV) only at very high Re : W ratios in solutions and the W content varies in one and the same sample. The dissolution of Re₂O₇ in the solutions of MO(OMe)₄, M = Mo,W in toluen on reflux yields Re_4–x M _x O_6–y (OMe)_12+y with uniform Re : M distribution. The cocrystallization of MoO(OMe)₄ and WO(OMe)₄ yields (Mo,W)O(OMe)₄ (V) with almost uniform Mo : W distribution. The thermal decomposition of II and III in inert atmosphere gives fine powder of the (Re,Mo)O₂ phase. The reduction with hydrogen gas converts II and III into an ultrafine powder of Re–Mo alloy at temperatures below 400°C. The latter can be sintered into compact metal at 800–900°C.     

Monitoring the Light-induced Isomerisation of the Prototypical Polycyclic Aromatic Hydrocarbons C10H8+ through Ion-Molecule Reactions

Structural rearrangements in ions are essential for understanding the composition and evolution of energetic and chemically active environments. This study explores the interconversion routes for simple polycyclic aromatic hydrocarbons, namely naphthalene and azulene radical cations (C₁₀H₈⁺), by combining mass spectrometry and vacuum ultraviolet tunable synchrotron radiation through the chemical monitoring technique. Products of ion-molecule reactions are used to probe C₁₀H₈⁺ structures that are formed as a function of their internal energies. Isomerisation from azulene radical cation towards naphthalene radical cation in a timescale faster than 80 μs was monitored, whereas no reverse isomerisation was observed in the same time window. When energising C₁₀H₈⁺ with more than 6 eV, the reactivity of C₁₀H₈⁺ unveils the formation of a new isomeric group with a contrasted reactivity compared with naphthalene and azulene cations. We tentatively assigned these structures to phenylvinylacetylene cations.     

Ionizing-Radiation Ignition of a Hydrogen–Air Mixture

The behavior of a hydrogen–air mixture under the action of ionizing radiation was studied. A kinetic model for radiation-chemical processes in the H₂–O₂–N₂ system was constructed, and the effects of the main parameters of radiolysis on shifting its flammability limits were analyzed. It was found that, under normal conditions (p = 0.1 MPa, T ₀ = 300 K), the ignition of the stoichiometric mixture began at a radiation intensity of about 0.1 kGy/s. The induction period of the chain H₂ oxidation reaction shortened with increasing radiation dose rate and pressure.     

Spectrophotometric determination of micro amounts of tetrathionate via its oxidation with permanganate

The reaction conditions of tetrathionate with permanganate were investigated by varying reaction time, temperature and amounts of sulphuric acid and permanganate. Under the optimal conditions for the reaction of tetrathionate with permanganate, both penta- and hexathionate were also oxidised; each one mol of polythionates (S _x O ₆ ^2– x=4, 5 and 6) reacts with (x–1.5) mol of permanganate. The proposed method is based on the reaction of tetrathionate with a given excess amount of permanganate in a sulphuric acid medium and on the spectrophotometric measurement of the iodine as triiodide formed by the oxidation of iodide with the excess of permanganate. This method could be successfully applied to the determinations of tetrathionate (4 × 10^–7 to 2 × 10^–5 M), pentathionate (3 × 10^–7 to 1.43 × 10^–5 M) and hexathionate (2 × 10^–7 to 1.11 × 10^–5 M), and gave a higher sensitivity than any previous methods without solvent extraction.     

New organosols of nickel sulfides,palladium sulfides,manganese sulfide,and mixed metal sulfides and their use in preparation of semiconducting polymer-metal sulfide composites

Organosols of NiS, PdS, and MnS in N,N-dimethylformamide were prepared by reaction of the metal acetate with H₂S. Organosols of mixed-metal sulfides (Zn _x Cd_1–x S, Hg _x Cd_1–x S, Hg _x Cu_1–x S, Cd _x Mn_1–x S, Hg _x Mn_1–x S, Hg _x Cd_1–x S, and Mn _x Zn_1–x S) were similarly obtained by reaction of mixtures of the metal salts with H₂S. The organosol of Zn_0.5Cd_0.5S contained particle with two particle size distributions centered at 6.5 nm and 29 nm, as revealed by Ar laser-scattering analysis. The metal sulfides are recovered by addition of Et₂O to the organosols. Zn _x Cd_1–x S thus obtained shows magnetic susceptibility in the range 0.5×10^–6–2.3×10^–6 emug^–1 depending on thex value. Addition of polymers to the organosols affords semiconducting films of metal sulfide-polymer composites.