Thermal decomposition ofC-iodotetrazoles

Thermal decomposition of 1-substitutedC-iodotetrazoles in melt and solutions has been investigated. Thermal stabilities, kinetic and activation parameters, and compositions of products of thermolysis ofC-iodotetrazolcs depend on the substituent nature. The scheme of thermolysis ofC-iodotetrazoles has been suggested.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 68–71, January, 1996.     

Synthesis and thermal decomposition of ditetrazol-5-ylamine

Ditetrazol-5-ylamine (DTA) was synthesized from cyanuric chloride in four steps. The thermal decomposition of DTA in the solid state was studied by thermogravimetry, volumetry, mass spectrometry, IR spectroscopy, and calorimetry. Under isothermal conditions at 200–242 °C, thermal decomposition obeys the first order autocatalytic kinetics. The kinetic and activation parameters of DTA decomposition were determined. The composition of gaseous reaction products and the structure of condensed residue were studied. The thermal effect of thermal DTA decomposition is 281.4 kJ mol⁻¹. The nitrogen content in a mixture of gaseous products formed by the reaction in a temperature interval of 200–242 °C exceeds 97 vol.%. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1660–1664, July, 2005.     

Amine electrosynthesis from 1-ethyl-4-nitro-3-cyanopyrazole

Polarography and preparative electrolysis are used to show that the electrochemical behavior of 1-ethyl-4-nitro-3-cyanopyrazole (1) in acidic aqueous-alcoholic solutions resembles the behavior of nitrobenzene. By varying the parameters of the electroreduction (ER) of compound 1, one can obtain either 1-ethyl-4-amino-3-cyanopyrazole (2) or 1-ethyl-4-amino-3-cyano-5-chloropyrazole (3). Compound 2 is formed during the ER of compound 1 in the presence of a mediator (titanium(III)) at temperatures below 10°C. Compound 3 is produced by the direct reduction of compound 1 on a lead electrode (30% ethanol, 10% HCl). The yield of amine chlorohydrates 2 and 3 is 56 and 92%, respectively. The mediated ER of compound 1 at catholite temperatures higher than 10°C yields a mixture of compounds 2 and 3; the proportion of the latter increases with temperature to become the major product at 60°C. Compound 3 is formed due to the rearrangement of the hydroxylamine derivative produced by the ER of compound 1, followed by the substitution of chlorine for the hydroxy group.     

Synthesis and Crystal Structure of Methyl 3-（5- Bromo-1-ethyl-1H-indole-3-carbonyl）aminopropionate

Methyl 3-(5-bromo-1-ethyl-1H-indole-3-carbonyl)aminopropionate has been syn-thesized by the acylation of 5-bromo-3-trichloroacetylindole with β-alanine methyl ester,followed by alkylation with ethyl iodide,in 82.6% yield.Its crystal structure was gotten and determined by X-ray diffraction method.The crystal is of monoclinic,space group P2 1 /c with a=11.7927(8),b=14.9342(8),c=9.0060(5),β=101.558(6)°,V=1553.93(16)3,Z=4,D c=1.510 g/cm 3,λ=0.71073,μ(MoKα)=2.656 mm-1,M r=353.22 and F(000)=720.The structure was refined to R=0.0401 and wR=0.0825 for 1704 observed reflections with I > 2σ(I).In the crystal structure,intermolecular N(2)-H(2)···O(1) hydrogen bond and weak intermolecular bonds (C(1)-H(1) O(1) and C(10)-H(10B) O(2)) are formed,and π-π stacking also exists.     

Thermal decomposition of deuterofullerite

The volative products of thermal decomposition of deuterofullerite C₆₀D₁₉ were studied by mass spectrometry. It was found that D₂, CD₄, and C₆D₆ molecules are present in the gas phase above deuterofullerite heated to 773 K. Deuterocarbons appear in the gas phase already at 673 K.     

The kinetic regularities, products, and mechanism of the thermal decomposition of dimethyldioxirane. The contribution of molecular and radical reaction channels

The products and kinetics of the thermal decomposition of dimethyldioxirane (DMDO) were studied. The reaction proceedsvia three parallel pathways: isomerization to methyl acetate, oxygen atom insertion into the C−H bond of a solvent molecule (acetone), and the solvent-induced homolysis of the O−O bond in the DMDO molecule. The contribution of the latter reaction channel isca. 23% at 56°C. The overall kinetic parameters of DMDO thermolysis in oxygen atmosphere were determined. The free radical-induced DMDO decomposition occurs in an inert atmosphere. The formal kinetics of this reaction was investigated. The mechanism of the DMDO thermolysis is discussed. Dedicated to Professor E. T. Denisov on the occasion of his 70th Birthday. Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1344–1354, August, 2000.     

Catalytic transformations of 1-octanol and 2-ethyl-1-hexanol over oxide catalysts, 1. Transition metal oxides as catalysts

A comparative study of 1-octanol and 2-ethyl-1-hexanol transformations over silica supported NiO, MnO₂, Cr₂O₃, Fe₂O₃, and ZnO has been performed. Zinca containing catalyst was found to be the most active in dehydrogenation and dehydration of the alcohols studied. ZnO dehydrogenating activity increased with supported oxide load.     

Kinetics of thermal decomposition of dimethyldioxirane in oxygen atmosphere

Dimethyldioxirane decomposition in oxygen atmosphere follows a first-order kinetic law. Decomposition rate constant (k, s⁻¹) in acetone in the temperature range from 30 to 50°C has been determined as lgk=(7.1±0.9)−(16.0±1.4)/θ, θ=2.303RT kcal/mol.     

Detection of 5-(3, 4-Dihydroxy-1, 5-Cyclohexadien-1-Yl) -5-Phenylsydantoin as a Major Metabolite of 5, 5-Diphenylhydantoin (Dilantin) in the Newborn Human

Abstract

The metabolism of 5, 5-diphenylhydantoin was studied in the newborn human in two instances; one involved direct administration of the drug, and the other was by placental transfer of the drug from the mother. 5-(3,4-Dihydroxy-1, 5-cyclohexadien-1-yl)-5-phenylhydantoin was found to be a major metabolite. The GC and GC-MS methods employed here are well suited to the problem of studying drug metabolism in the newborn.     

Thermal decomposition of polypyrroles

The thermal stability of polypyrrole (PPy) samples has been studied by thermogravimetry/mass spectrometry and pyrolysis-gas chromatography/mass spectrometry in inert atmospheres. PPy has been prepared by chemical oxidative polymerization using ferric sulfate as an oxidant and anionic surfactants, such as dodecylbenzenesulfonic acid and sodium dodecylbenzenesulfonate as co-dopants. For comparison we have studied polypyrrole (PPy-SO₄) prepared without any additive. It was found that the presence of anionic surfactants improved the thermal stability of PPy. The decomposition of PPy doped with ferric sulfate and anionic surfactants occurs at relatively high temperature indicating that chemical interactions exist between the polymer and the surfactants.     

Thermal decomposition kinetics of strontium oxalate

The thermal decomposition behavior in air of SrC₂O₄ · 1.25H₂O was studied up to the formation of SrO using DTA-TG-DTG techniques. The decomposition proceeds through four well-defined steps. The first two steps are attributed to the dehydration of the salt, while the third and fourth ones are assigned to the decomposition of the anhydrous strontium oxalate into SrCO₃ and the decomposition of SrCO₃ to SrO, respectively. The exothermic DTA peak found at around 300°C is ascribed to the recrystallization of the anhydrous strontium oxalate. On the other hand, the endothermic DTA peak observed at 910°C can be attributed to the transition of orthorhombic-hexagonal phase of SrCO₃. The kinetics of the thermal decomposition of anhydrous strontium oxalate and strontium carbonate, which are formed as stable intermediates, have been studied using non-isothermal TG technique. Analysis of kinetic data was carried out assuming various solid-state reaction models and applying three different computational methods. The data analysis according to the composite method showed that the anhydrous oxalate decomposition is best described by the two-dimensional diffusion-controlled mechanism (D₂), while the decomposition of strontium carbonate is best fitted by means of the three-dimensional phase boundary-controlled mechanism (R₃). The values of activation parameters obtained using different methods were compared and discussed.     

Kinetics of no decomposition over Cu/ZSM-5 catalyst

The kinetics of catalytic decomposition of NO over Cu/ZSM-5 catalyst has been studied in an integral flow reactor at atmospheric pressure. Kinetic analysis is based on the assumption that the surface reaction represents the rate-determining step. On the basis of theoretical considerations of different interactions between reactants and catalyst, and experimental evidences, three different mechanistic kinetic models were chosen. Also a power-law model was tested. The best agreement has been achieved with the model

Skeletal transformations of perfluoro-1-ethyl-1-phenylbenzocyclobutene in the reaction with antimony pentafluoride

Interaction of perfluoro-1-ethyl-1-phenylbenzocyclobutene with SbF₅ at room temperature gives, after treatment of the reaction mixture with H₂O, perfluoro-4-[1-(2-methylphenyl)propylidene]cyclohexa-2,5-dienone as a main product. The reaction at 90-95 °C leads, after treatment with H₂O, to a mixture of perfluorinated 9-ethyl-9-methyl-1,2,3,4-tetrahydro-9H-fluorene, 9-ethyl-4a-methyl-4,4a-dihydrofluoren-1-one, 3-ethyl-3-phenylphthalide, 1-hydroxy-2-methyl-1-phenylindan, 3-methyl-2-phenylindenone and small amounts of other products.     

Catalytic transformations of 1-octanol and 2-ethyl-1-hexanol over oxide catalysts, part II. Promoted zinc oxide as a catalyst

Silica supported ZnO was modified with alkaline promoters to reduce its dehydrating activity towards 1-octanol and 2-ethyl-1-hexanol. Neutralization of zinca acidic centers led to the significant decrease of the yields of alkenes formed during dehydration. Simultaneously, the enhancement of ZnO dehydrogenating activity was observed. The effect of modifier diminished in the sequence: K₂CO₃>KOH>Na₂CO₃.     

Thermal decomposition mechanism of 1-ethyl-3-methylimidazolium bromide ionic liquid

In order to better understand the volatilization process for ionic liquids, the vapor evolved from heating the ionic liquid 1-ethyl-3-methylimidazolium bromide (EMIM(+)Br(-)) was analyzed via tunable vacuum ultraviolet photoionization time-of-flight mass spectrometry (VUV-PI-TOFMS) and thermogravimetric analysis mass spectrometry (TGA-MS). For this ionic liquid, the experimental results indicate that vaporization takes place via the evolution of alkyl bromides and alkylimidazoles, presumably through alkyl abstraction via an S(N)2 type mechanism, and that vaporization of intact ion pairs or the formation of carbenes is negligible. Activation enthalpies for the formation of the methyl and ethyl bromides were evaluated experimentally, ΔH(?)(CH(3)Br) = 116.1 ± 6.6 kJ/mol and ΔH(?)(CH(3)CH(2)Br) = 122.9 ± 7.2 kJ/mol, and the results are found to be in agreement with calculated values for the S(N)2 reactions. Comparisons of product photoionization efficiency (PIE) curves with literature data are in good agreement, and ab initio thermodynamics calculations are presented as further evidence for the proposed thermal decomposition mechanism. Estimates for the enthalpy of vaporization of EMIM(+)Br(-) and, by comparison, 1-butyl-3-methylimidazolium bromide (BMIM(+)Br(-)) from molecular dynamics calculations and their gas phase enthalpies of formation obtained by G4 calculations yield estimates for the ionic liquids' enthalpies of formation in the liquid phase: ΔH(vap)(298 K) (EMIM(+)Br(-)) = 168 ± 20 kJ/mol, ΔH(f,?gas)(298 K) (EMIM(+)Br(-)) = 38.4 ± 10 kJ/mol, ΔH(f,?liq)(298 K) (EMIM(+)Br(-)) = -130 ± 22 kJ/mol, ΔH(f,?gas)(298 K) (BMIM(+)Br(-)) = -5.6 ± 10 kJ/mol, and ΔH(f,?liq)(298 K) (BMIM(+)Br(-)) = -180 ± 20 kJ/mol.     

Thermal decomposition behavior of naphthalene-labeled polyethylene

Pyrolysis–GC/mass spectrometry experiments reveal that naphthalene groups attached to maleated polyethylene as the 1-naphthylethyl ester are stable for relatively long periods of time at 170°C. Decomposition can be detected for samples heated for 2.0 min at 200°C, but even at that temperature, the extent of decomposition is very small. At higher temperatures, two of the decomposition products from the labeled polymer are readily understood: 1-vinylnaphthalene and 1-naphthylethanol can form by reactions that are well-precedented in the organic chemistry literature. At 200°C, only naphthalene is formed, which requires scission of the bond between the naphthyl ring and the C₁ carbon of the ethyl group. We suggest two possible pathways for this reaction. © 1996 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 34:2045–2049, 1996     

R?ntgenstruktur-Analyse von Trans-1-ethyl-2-(1-ethyl-2-adamantyliden)adamantan, Vergleich mit Kraftfeld-Rechnungen

Ohne Zusammenfassung

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X-ray structural analysis of trans-1-Ethyl-2-(1-ethyl-2-adamantylidene)-adamantane. Comparison with force field calculations

     

Laser photolysis of 1-(4-nitrophenyl)-3-methylpyrazole and 1-ethyl-3-(4-nitrophenyl)-5-chloropyrazole

The spectral kinetic characteristics of the triplet states of 1-(4-nitrophenyl)-3-methylpyrazole (1) and 1-ethyl-3-(4-nitrophenyl)-5-chloropyrazole (2) were studied by the laser nanosecond photolysis technique in different solvents. The triplet lifetimes (τ_T) of molecules 1 and 2 were found to depend strongly on the solvent nature. An increase in τ_T by approximately two orders of magnitude on going from nonpolar and polar aprotic solvents (τ_T ≤ 15 ns) to aqueous-acetonitrile solutions (τ_T = 1100 ns for a volume acetonitrile to water ratio of 1 : 3) was analyzed, taking into account the influence of the medium on the relative contribution of the n,π*- and π,π*-configurations to the lowest triplet state. __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1115–1119, May, 2005.     

Thermal decomposition of copper complexes of 1-phenyl-3-methyl-4-acyl-5-pyrazolone in air atmosphere

Copper complexes of some 1-phenyl-3-methyl-4-acyl-5-pyrazolones have been prepared. The complexes were characterized by elemental analyses and thermal analyses. It was shown that the melting points decrease linearly in increasing the molecular weight of the complexes.     

Non-isothermal Kinetics of the Thermal Decomposition of 3-Nitro-1,2,4-triazol-5-one Magnesium Complex

Introduction3 Nitro 1,2 ,4 triazol 5 one (NTO)metalcomplexeshavemanyspecialstructuresandsomepotentialusesinammunition .1 4 Wepreviouslypreparedanddeterminedthecrystalstructureofitsmagnesiumcomplex ,5andinthispaper ,wediscusseditsthermalbehaviorbyDSCandTG/DTGtechniquesandstudieditsnon isothermalkineticsbythemeansoftheKissingermethod ,theOzawamethod ,thedifferentialmethodandtheintegralmethod .ExperimentalSample[Mg(H2 O) 6 ](NTO) 2 ·2H2 Owaspreparedasfollows :AcalculatedamountofMg(OH…