Multiphoton dissociation of C3F6O

Major characteristics of multiphoton absorption and multiphoton dissociation of hexafluoropropene oxide (HFPO) were studied. Spectral relationships of the average number of IR photons absorbed per molecule and the yield of multiphoton dissociation were determined in the range of 1040-985 cm^–1 at different laser fluences. At the laser line 1025.3 cm^–1, the effect of collisions with buffer gases on the HFPO multiphoton absorption and multiphoton dissociation was studied and theq-factor was determined (q = O.6 at= 0.55J cm^–2). Characteristic features of HFPO decomposition under collisional conditions (p _HFPO> 0.1 Torr) were discussed. An anomalous difference in the values for quantum efficiency of multiphoton dissociation for long-wave and short-wave wings of HFPO absorption band was revealed. A procedure for correlating the experimental and theoretical data on the yield of multiphoton dissociation (when theq-factor is unknown) was suggested, and corresponding calculations were performed for the frequency 989.6 cm^–1.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1927–1932, November, 1994.     

Solvent and chelation effects on the photoreduction of cobalt(III)–amine complexes in aqueous–organic solvent media

The photoreduction of trans-[Co(NH₃)₄Cl₂]⁺, trans-[Co(en)₂Cl₂]⁺, [Co(dien)Cl₃], [Co(trien)Cl₂]⁺, and [Co(tetren)Cl]²⁺, ions has been studied using a low pressure Hg vapour lamp as light source (254 nm) in aqueous–organic solvents [0–30% (v/v) MeOH or 1,4-dioxane]. Quantum yields for Co^II production by redox decomposition have been determined in all the cases, and increase considerably with the increase in concentration of MeOH or 1,4-dioxane in the binary solvent mixtures under investigation. A plot of log(quantum yield) versus the Grunwald–Winstein Parameter, Y, which is a measure of solvent ionizing power, shows that a different blend of general and specific solvent interacts with the solute. This kind of specific solvent interaction on the reactant/excited state has been analysed using multiple regression: viz. Krygowski–Fawcett and Kamlet–Taft equations. Reasons for the difference in reactivity with chelation are also discussed.     

Long-wave light absorption and photochemical decomposition of peroxide radicals

Photochemical decomposition of alkylperoxide radicals in glassy matrices at 77 K was experimentally studied. Irradiation with light up to 405 nm leads to the photodecomposition of peroxide radicals. The quantum yield of the reaction was estimated to be 10^–2. A light-induced angular dependence of the ESR spectra of peroxide radicals resulting from photoselection was detected. The photoselection found proves that the photodecomposition is induced by the absorption of light in the inherent absorption band of RO₂.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1074–1077, June, 1995.The work was carried out with the financial support of the Russian Foundation for Basic Research (Project No. 95-03-08505) and the International Science Foundation (Grants NBU 000 and NBU 300).     

Structure and thermal stability of difluoroamino compounds in the liquid state

The kinetics of decomposition of 15 difluoroamino compounds with NF₂ groups at primary, secondary, and tertiary carbon atoms in the liquid state was investigated. Activation energies (E _a) for all of the compounds were in the interval 100–120 kJ · mol^–1. The reaction rate does not depend on the electronic effects of the substituents and decreases only in the case of steric shielding of the NF₂ group. ForN-difluorobenzylamine it was shown that the gas-phase elimination of HF is characterized byE = 176 kJ·mole^–1, while the rate of decomposition in a solution depends on the dielectric constant of the medium. Based on the results obtained, a mechanism for liquid-phase decomposition, which involves heterolysis of the N-F bonds, is suggested.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 336–338, February, 1994.     

Rf plasma processing of silica

The processing of silica in an rf plasma was studied with a new experimental system, the process being carried out entirely in the vapor phase. SiO and Si were obtained by either thermal decomposition of SiO₂ or reduction by H₂. No other reducing material (which, like C, may become a contaminant) was used. The products were collected along the reactor length and analyzed afterward. Temperatures in the reaction zone were measured spectroscopically. The high reaction rates occurring in the gas phase did compensate for the low residence times. A diffusional model for the buildup of solid reaction products is discussed. Vapor phase plasma reduction of silica with hydrogen proved to be more effective than thermal decomposition and nuch more effective than heterogeneous processing. The efficiency evaluation was made on the laboratory-scale level.Nomenclature c _SiO ^d SiO content, % by wt - c _Si ^t Total Si content, % by wt - cSiO ₂ ^e Experimental SiO₂ content, % by wt - cSiO ₂ ^t Theoretical SiO₂ content, % by wt - D Species diffusivity, cm² · sec^–1 - F Rate of species deposition, mol · cm^–2 · sec^–1 - MSiO₂ Molar flow of SiO₂, mmol · sec^–1 - n Species concentration, cm^–3 - P Anode power, kW - r Reaction radius, cm - R ^* Radius of quartz tube, cm - T Temperature, K - T _av Average temperature, K - USiO ₂ ^t Total extent of SiO₂ decomposition, % - V _Ar ^a Molar flow of axial Ar, mmol · sec^–1 - V _Ar ^p Molar flow of peripheral Ar, mmol · sec^–1 - VH₂ Molar flow of H₂, mmol · sec^–1 - y Molar fraction - Z Position of a plane normal to the plasma axis down the lower turn of rf coil, cm Greek Letters Molar ratio of SiO over SiO₂ in deposit     

Kinetics of limonene autooxidation

The kinetic parameters of the oxidizability of Iimonene,k _p/(2k _t)^0.5 = 6.0- 10^–3 L^{0 5} mol^–5 s^–0.5, and of the bimolecular radical decomposition of hydroperoxides 2ek _d = 6.0 · 10^–6 L mol^–1 s^–1 were determined at 60 °C The oxidation rate increases in the presence of micro additives of water. Average effective diameters of particles formed in the water-AOT-(n-decane + lirnonene) microemulsion were measured by the light scattering technique. The hydroperoxides were found to affect the size of the microemulsion particles.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya. No. 7, pp. 1682–1685, July. 1996.     

Radiation oxidation of phenol in the presence of petrochemical wastewater components

Radiolytical decomposition of phenol was investigated at⁶⁰Co gamma irradiation (1–2 Gy·s^–1, 10 kGy) of pre- and continuously aerated aqueous solutions at concentrations of phenol 1–100 mg· ·dm^–3 and in the presence of sodium hydroxide, sulphuric acid, sodium and ferrous sulphate, formaldehyde, 2-propanol,n-hexane, xylene, benzene, and commercial gasoline. From the decomposition rate at doses 50–400 Gy, a phenomenological model of linear relation between the dose acquired for 37% decomposition (D ₃₇), initial concentration (g·m^–3) of phenol (p ₀) and of an admixture (s ₀) was confirmed in the formD ₃₇=52f _tr(p ₀+f _eq s ₀), wheref's are constants which can be attributed to the relative transformation resistance of phenol towards the OH radicals in given matrix (f _tr, for pure waterf _tr=1) and relative acceptor capacity of competing substrate (f _eq). In real wastewaters, the efficient decrease of phenols content may be substantially lower than that in model solutions, obviously due to radiation oxidation of aromates, as proved by irradiation of aqueous solutions of benzene. Technical and economical feasibility of the process is discussed.     

The thermal dehydration and decomposition of Ba[Cu(C2O4)2(H2O)]·5H2O

The thermal behaviour of Ba[Cu(C₂O₄)₂(H₂O)]·5H₂O in N₂ and in O₂ has been examined using thermogravimetry (TG) and differential scanning calorimetry (DSC). The dehydration starts at relatively low temperatures (about 80°C), but continues until the onset of the decomposition (about 280°C). The decomposition takes place in two major stages (onsets 280 and 390°C). The mass of the intermediate after the first stage corresponded to the formation of barium oxalate and copper metal and, after the second stage, to the formation of barium carbonate and copper metal. The enthalpy for the dehydration was found to be 311±30 kJ mol^–1 (or 52±5 kJ (mol of H₂O)^–1). The overall enthalpy change for the decomposition of Ba[Cu(C₂O₄)₂] in N₂ was estimated from the combined area of the peaks of the DSC curve as –347 kJ mol^–1. The kinetics of the thermal dehydration and decomposition were studied using isothermal TG. The dehydration was strongly deceleratory and the -time curves could be described by the three dimensional diffusion (D3) model. The values of the activation energy and the pre-exponential factor for the dehydration were 125±4 kJ mol^–1 and (1.38±0.08)×10¹⁵ min^–1, respectively. The decomposition was complex, consisting of at least two concurrent processes. The decomposition was analysed in terms of two overlapping deceleratory processes. One process was fast and could be described by the contracting-geometry model withn=5. The other process was slow and could also be described by the contracting-geometry model, but withn=2.The values ofE _a andA were 206±23 kJ mol^–1 and (2.2±0.5)×10¹⁹ min^–1, respectively, for the fast process, and 259±37 kJ mol^–1 and (6.3±1.8)×10²³ min^–1, respectively, for the slow process.Dedicated to Prof. Menachem Steinberg on the occasion of his 65th birthday     

Mechanism of the monomolecular thermal decomposition of 1,5- and 2,5-disubstituted tetrazoles

The kinetic parameters of the thermal decomposition of several pairs of 1(2)-R-5-R-disubstituted tetrazoles have been determined using the manometric method. The isomers differ only by the position of the substituents linked with the heterocyclic nitrogen atom. The activation entropies are equal to ca. +8 cal mol^–1 K^–1, the activation energies range from 39 to 48 kcal mol^–1. A linear correlation between the logarithms of the rate constants of decomposition of the isomers has been established. The limiting stages of the stepwise mechanism of the monomolecular decomposition, which determines the experimental rates of nitrogen evolution, include the reversible formation followed by decomposition of intermediate azidoazomethines in the case of 1,5-disubstituted tetrazoles and azodiazo compounds for isomeric 2,5-disubstituted tetrazoles. The enthalpies of formation of R(N₃)C=NR (R = Me, Ph), C₂H₃(N₃)C=NMe and increments _f H°[C_d–(C)(N₃)], _f H°[C_d-(C_b)(N₃)], and _f H°[C_d–(C_d)(N₃)] have been estimated.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2209–2215, September, 1996.     

Oxidation of diazo compounds by triphenyl phosphite ozonide. Quenching of singlet oxygen by diazo compounds

The reaction of triphenyl phosphite ozonide with various types of diazo compounds results in their oxidation, which is accomplished by singlet oxygen (¹O₂) evolved during thermal decomposition of the ozonide. A decrease in the ionization potential of the substrate results in an increase in the overall rate constant of quenching of¹O₂. In the case of 9-diazofluorene, the main channel of¹O₂ quenching is physical quenching.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1567–1571, September, 1994.The work was carried out with the financial support of the Russian Foundation for Basic Research (Project No. 93-03-5231).     

A new method for generating organosilanones

A new method for the generation of organosilanones by the reaction of betaines, R₃P⁺-CR¹R²-SiR³R⁴-S^–, with (Et₃Sn)₂O was suggested.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2246–2247, December, 1994.This study was financially supported by the Russian Foundation for Basic Research, Project No. 94-03-09710.     

Tensimetric investigation of the CrCl<Subscript>3</Subscript>—Cl<Subscript>2</Subscript> system in the temperature range of 600–1200 K

The sublimation pressure of chromium trichloride was measured by the static method with a quartz membrane-gauge manometer in the temperature range of 875–1230 K. An approximating equation for the sublimation pressure vs. temperature was found. The enthalpy (259.4±4 kJ mol^–1) and the entropy (224.2±3.5 J mol^–1 K^–1) of sublimation at 298 K were calculated. For the process 2 CrCl₃(g) + Cl₂(g) = 2 CrCl₄(g), the following values were obtained: _r H°₂₉₈ = –207.1±11.6 kJ mol^–1 and _r S°₂₉₈ = –173.6±10 5 J mol^–1 K^–1.Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1561–1564, August, 2004.     

Activation of the C-O bond on the surface of palladium: An <Emphasis Type="Italic">In situ</Emphasis> study by X-ray photoelectron spectroscopy and sum frequency generation

An in situ study of the adsorption of CO on atomically smooth and defect Pd(111) surfaces was performed over wide ranges of temperatures (200–400 K) and pressures (10^–6-1 mbar) by X-ray photoelectron spectroscopy and sum frequency generation. Both of the techniques indicated that CO was adsorbed as three-fold hollow, bridging, and terminal species to form well-known ordered structures on the surface. In the course of the in situ experiments, no signs of CO dissociation or of the formation of carbonyl structures (Pd(CO)_n, n > 1) were detected. The mechanism of C-O bond activation in the course of methanol decomposition on the surface of palladium was considered. It was found that the adsorption of methanol on the surface of palladium essentially depends on pressure. Along with the well-known reaction path of methanol dehydrogenation to CO and hydrogen, a slow process of methanol decomposition with C-O bond cleavage was observed at elevated pressures. In this case, the formation of carbon deposits finally resulted in the carbonization and complete deactivation of the surface. A mechanism for C-O bond activation on the surface of palladium was proposed; the geometry of adsorption complexes plays an important role in this mechanism.__________Translated from Kinetika i Kataliz, Vol. 46, No. 2, 2005, pp. 288–301.Original Russian Text Copyright © 2005 by Kaichev, Bukhtiyarov, Rupprechter, Freund.     

The effect of high pressure on the ion pair equilibrium constant of alkali metal fluorides: A spectrophotometric study

Bromophenol blue indicator was used in UV-visible spectrophotometric measurements to study ion association constants of alkali metal fluorides. The equilibrium constants for the ion pair formation of the alkali metal fluorides were determined as a function of ionic strength at one atmosphere pressure and 25°C. The effect of pressure on these association constants was measured at a constant total ionic strength of 1.0 mol-kg^–1 over a pressure range of 1 to 2000 atmospheres at 25°C. The pressure dependences of the stoichiometric association constants of the alkali metal fluorides are given by: lnK _LiF ^* =0.77–2.47×10^–4P–2.12×10^–8P²; lnK _NaF ^* =0.53–1.08×10^–4P–1.66×10^–8P²; lnK _KF ^* =0.24–4.41×10^–5P–7.15×10^–8P²; lnK _RbF ^* =–0.17–8.65×10^–5P–4.51×10^–8P²; and lnK _CsF ^* = –0.37–1.14×10^–4P–6.82×10^–8P², where P is the pressure in atmospheres. The stoichiometric molar volume and compressibility changes for ion pair formation of the alkali metal fluorides were evaluated from the pressure dependence of K _MF ^* data. The thermodynamic association constants were also calculated making use of activity coefficient data from the Pitzer equations. The partial molal volume and compressibility changes for ion pair formation of each alkali metal fluoride are reported.     

Selective method for the preparation of 5-chloropentan-2-one

A selective method for the preparation of 5-chloropentan-2-one by interaction of 1-methylcyclobutanol with Ca(OCl)₂ followed by decomposition of the hypochlorite thus obtained in the presence of Fe^II salt is proposed. The selectivity of the ketone formation from the alcohol is 98%, while the conversion of the alcohol is 35–40%.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 774–776, April, 1995.     

Thermal transformations in systems based on zeolites Y,X, and A containing zinc and sodium nitrates

Thermal transformations in systems formed by interaction of Zn and Na nitrates with Y, X, and A zeolites were studied by TG—DTA technique. Temperature regions of existence of adsorbed water, water of crystallization, and decomposition of NO₃ ^– anion were determined. These intervals depend on the composition, structure, method of preparation, and pre-treatment conditions of zeolite systems. The extent of NO₃ ^– decomposition depends not only on the zinc and sodium content but also on the presence of ammonia involved in NO₃ ^– reduction. The zeolite matrix strongly stabilizes the occluded NO₃ ^– anions. A portion of zinc oxide formed by zinc nitrate decomposition is probably localized inside the zeolite cavities as the [Zn—O—(ZnO) _n —Zn]²⁺ particles. The latter compensate charges of the isolated [AlO₄]^– tetrahedra.     

Induced free-radical chain decomposition of dimethylacetamide hydroper oxide in dimethylacetamide as the medium

Conclusions The thermal gross decomposition of dimethylacetamide hydroperoxide (ROOH) in dimethylacetamide (RH) as the medium proceeds in harmony with the equation: W_p=k_ind [ROOH]₀ ^m/[RH]₀ ⁿ, where m=1.5–2; n=2–0.5. Alkyl radicals with a chain length of 195–3 units are mainly responsible for the induced decomposition. We determined the ratio between the molecular and radical directions of the decomposition and k_ind in the range 80–132°.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 967–970, April, 1978.     

Synthesis and NMR spectra of the hydroxyundecahydro-closo-dodecaborate [B12H11OH]2− and its acylated derivatives

Tetrabutylammonium hydroxyundecahydro-closo-dodecaborate was obtained in high yield via [B₁₂H₁₁NMP]^–(NMP =N-methylpyrrolidone) by the modified method. [B_i2H₁₁OH]^2– is easily acylated by aromatic acyl chlorides to give novel compounds [B₁₂H₁₁OCOAr]^2– in high yields. All the compounds were characterized by standard and special NMR methods.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 722–725, March, 1996.     

Infrared multiphoton decomposition of highly excited t-butyl chloride-d9

The infrared multiphoton decomposition (IR MPD) of t-butyl chloride-d₉ as a function of pressure and fluence is reported. The major decomposition route was molecular elimination of DCl in accord with earlier pyrolysis studies. The effect of added gases (2-methyl propene-d₈, DCl and 2-methyl propene-h₈) on the MPD is presented. This study is a further example of the utility of a new method of analysis of MPD experiments. © 1994 John Wiley & Sons, Inc.     

A field-desorption study of thermal stability in potassium pentacyanocobaltates(III)

Field desorption has been applied to research the thermal stability of the compounds K_n[Co(CN)₅X], where X=SO₃ ^2–, CN^–, NO₂ ^–, NO^–, Cl^–, Br^–, I^–, and H₂O. A likely mechanism is proposed for the thermal decomposition. There is a correlation between the tetragonal-distortion parameters and the temperature of onset of destruction for the [Co(CN)₅X]^n– anion.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 21, No. 1, pp. 111–115, January–February, 1985.