Thermal decomposition of 2,4,6-trinitrotoluene in melt and solutions

Thermal decomposition of 2,4,6-trinitrotoluene in the temperature range from 200 to 340 °C in melt and in solutions was studied. The main features of the process (high initial rates, activation energies lower than those in the gaseous phase, a higher acceleration at the catalytic stage, and the effect of nonpolar solvents on initial rates) are explained in terms of a kinetic scheme corresponding to a degenerate branched chain reaction.Translated fromIzyestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 266–271, February, 1995.     

Chain decomposition of 2,4,6-trinitrotoluene in hydrocarbon solvents

The rate constants for the thermal decomposition of 2,4,6-trinitrotoluene have been measured in toluene and other hydrocarbon solvents. The initial, observed rate constant (k _i) increases with dilution with toluene. The concentration dependence is described by the chain decomposition scheme with the transfer of the free valence to a solvent molecule. The activation energy and logk _i were found to linearly correlate with the dissociation energy of the C-H bond of the solvent.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1977–1980, August, 1996.     

Mechanism of the monomolecular thermal decomposition of tetrazole and 5-substituted tetrazoles

The kinetic parameters of the thermal decomposition of tetrazole and 5-alkyl- and 5-aryl-substituted tetrazoles in melts of neat substances and in nitrobenzene solutions have been determined using the manometric method. The limiting stages of the monomolecular decomposition, which determine the observed rate of nitrogen formation, include the fast reversible transformation of the lH- and 2H-forms and the reversible opening of the 2H-form followed by the formation and subsequent cleavage of the corresponding intermediate diazo compound.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2216–2219, September, 1996.     

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.     

新型单组份磷-氮膨胀型阻燃剂的热分解动力学

利用热重分析法研究了在不同升温速率下新型单组份磷-氮膨胀型阻燃剂六(4-(9,10-二氢-9-氧杂-10-磷杂菲-10-氧化物)-羟甲基苯氧基)环三磷腈(DOPOMPC)在氮气气氛和空气气氛中的热分解动力学.采用Kissinger和Flynn-Wall-Ozawa(FWO)法分别计算出DOPOMPC在相应气氛下的活化能和指前因子.     

The monomolecular mechanism of the gas‐phase thermal decomposition of primary N‐nitramines

Using nonempirical methods and DFT‐methods the geometrical parameters formation enthalpies of molecules and radicals, energies dissociation of N? NO₂ bonds of primary and secondary N‐nitramines have been investigated. The basic tendencies in the changes of the geometrical and electronic structures, formation enthalpies, and dissociation energies have been analyzed in basic homologous series of nitramines. Various alternative mechanisms of the gas‐phase monomolecular thermal decomposition have been studied by of the example of N‐methylnitramine. The process of the aci‐form formation and its further multistage destruction is the most advantageous way of decomposition of the primary N‐nitramines. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

Thermal decomposition of lighter lanthanide selenate hydrates and their solid solutions

The thermal dehydration-decomposition of Ln₂(SeO₄)₃·nH₂O (wheren=12 forLn=Pr, Nd andn=8 forLn=Sm) and Pr_xLn_2−x(SeO₄)₃·nH₂O (wheren=12 forx=1.0 andLn=Nd;n=8 forx=0.2 and 1.0 in case ofLn=Sm) have been reported.

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Zusammenfassung Die thermische Dehydratation-Zersetzung von Ln₂(SeO₄)₃·nH₂O (mitn=12 fürLn=Pr, Nd undn=8 fürLn=Sm) und Pr_xLn_2−x(SeO₄)₃·nH₂O (mitn=12 fürx=1.0 undLn=Nd;n=8 fürx=0.2 und 1.0 in Falle vonLn=Sm) wurde beschrieben.

     

Mechanism of formation and monomolecular decomposition of aci-nitromethanes: a quantum-chemical study

A quantum-chemical study of the reactions of formation of aci-nitromethane (aci-NM) and aci-dinitromethane (aci-DNM) and their decomposition with elimination of water was carried out. The methods employed were the ab initio RHF method with inclusion of electron correlation at the MP2 level of theory and the Dunning—Hay double zeta basis set augmented with polarization d-functions on heavy-element atoms, the DFT approach at the B3LYP level, and the semiempirical PM3 method. The formation of aci-NM and aci-DNM was found to be the limiting stage of the mechanism under study. For DNM, the barrier to reaction is substantially lower than for NM. The estimates of the heights of the barriers to formation found from density functional calculations at the B3LYP/6-311++G(df,p) level (258 kJ mol^–1 for aci-NM and 218.5 kJ mol^–1 for aci-DNM) are thought to be the most reliable.     

纳米氧化钕的制备及其催化性能的研究

Nanometer-sized neodymium oxide has been synthesized by humid solid state reaction at room temperature， and characterized by scanning electron microscope， laser light scattering and X-ray diffraction. The effects of nanometer -sized neodymium oxide on catalyzing thermal decomposition reaction of hexogen (cyclotrimethylenetriamine， RDX) and absorbent powder (nitrocellulose absorbed nitroglycerin， NC/NG) have been investigated by DSC method. The mechanism of these catalytic reactions has also been proposed. The experimental results show that nanometer-sized neodymium oxide can catalyze the decomposition reaction of RDX and NC/NG effectively. The experimental results further suggest that nanometer-sized neodymium oxide is a potentially useful combustion catalyst of nitroamine propellant.     

Catalytic decomposition of hydrogen peroxide in alkaline solutions

Catalytic activity of carbon, platinum-supported on high-area carbon, platinum, lead ruthenate, and ruthenium oxide towards hydrogen peroxide decomposition in alkaline solution is investigated using the rotating disk electrode technique. The heterogeneous rate constant for peroxide decomposition on these catalysts is determined from the slope of log(i_L) versus time, where i_L is the diffusion-limiting current corresponding to the concentration of peroxide at a given time. The order of catalytic activity is found to be platinum>lead ruthenate>ruthenium oxide>carbon. A general reaction mechanism for the peroxide decomposition on these catalysts is also proposed.     

Theoretical investigation of the decomposition of monofluoromethanol

Ab initio calculations have been used to study the decomposition pathways of monofluo-roinethanol. Equilibrium geometries and transition state structures were optimized at the HF/6-31G(d) and MP2/6-31G(d) levels. Single point energies were obtained at different levels of theory. The most favorable reaction to dissociation is the 1,2-HF elimination which is consistent with the experimental results.     

Old and new studies of the thermal decomposition of potassium permanganate

The overall chemical equation representing the thermal decomposition of potassium permanganate up to ≈300°C is given approximately by: 10 KMnO₄→2.65 K₂MnO₄+[2.35 K₂O·7.35·MnO_2.05]+6O₂, the bracketed material being δ-MnO₂. The experimental mass loss in air is ≈12% and the enthalpy of decomposition is ≈10 kJ/mol of KMnO₄. Analysis of published kinetic studies of the decomposition show that most of the results can be represented by the Prout-Tompkins equation ln (x/(1−x))=k _{T t}+constant, and insertion of the rate constants into the Arrhenius equation gives an activation energy for decomposition of ≈150 kJ/mol of KMnO₄. Although the kinetic studies have always been interpreted in terms of a single type of chemical decomposition, with the different rates encountered during the course of the decomposition ascribed to physical effects, X-ray diffraction studies by Boldyrev and co-workers have shown that the reaction actually occurs in two stages, with essentially all the KMnO₄ transformed into K₃(MnO₄)₂, δ-MnO₂ and O₂ in the first stage, and the K₃(MnO₄)₂ then decomposing into K₂MnO₄ and more δ-MnO₂ and O₂ in the second stage. We have confirmed the Boldyrev diffraction results and extended them by measuring the kinetics of the appearance and disappearance of K₃(MnO₄)₂ by an X-ray diffraction method. Our earlier isotopes studies have shown that the oxygen molecules come from oxygen atoms produced by breaking Mn−O bonds in different permanganate ions i.e. the decomposition mechanism is interionic. We conclude by summarising what is, and is not, currently known about the thermal decomposition of potassium permanganate up to ≈300°C. In celebration of the 60^th birthday of Dr. Andrew K. Galwey     

Thermal decomposition of transition metal carboxylates

Thermal decomposition of anhydrous Cu(HCOO)₂ (1) affords H₂, CO, CO₂, H₂O, HCuOOH, CuHCOO, Cu, and the polymeric product, which contains -CH₂O,-C(O)OH-, and -RCH-0- groups. Dccomposition of1 proceeds in stages with formation of copper(I) formate as an intermediate. Possible pathways of decomposition ofI, including isomeric forms of the HCO₂ radical as intermediates, were analyzed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1406–1412, June, 1996.     

Thermal decomposition of basic copper sulphate monohydrate

The thermal decomposition of copper sulphate hydroxide hydrate, (CuO·CuSO₄). 2Cu(OH)₂·H₂O, to copper oxysulphate and CuO was investigated by X-ray phase analysis, IR spectroscopy, complex thermal analysis and electron microscopy. The effect of water vapour and time of treatment on the formation of decomposition products with a large surface area is studied. The strong decrease in specific surface area of the precipitate (from 80 m²/g to 20 m²/g) thermally treated at a temperature above 250°C is associated with the elimination of water having a coordination bond with the Cu²⁺ ion. During this process, the interplanar distances of the crystal lattice of copper sulphate hydroxide hydrate decrease. The time of decomposition of this compound essentially affects the decrease of the specific surface area. When the decomposition proceeds in an atmosphere containing water vapour sintering processes are predominating and the phase obtained has a considerably smaller specific surface area than in cases of decomposition under dry air.     

硫酸铵的热分解

目前 ,关于各种无机酸铵盐的热分解情况都研究得比较清楚 ,但关于硫酸铵热分解情况的报道结果则不一致[1 - 7] 。本文对硫酸铵在各种温度下的常量热分解进行了研究 ,探讨其热分解机理 ,以利于对磷石膏 (主要成分为ＣａＳＯ4)的开发利用提供新的思路和方法[8] 。1　实验坩锅炉中热分解　约 1 0ｇ(ＮＨ4) 2 ＳＯ4置于恒重坩埚中 ,再放入坩埚炉中升温至设定温度 ,恒温0 5ｈ ,取出冷却 ,称重。并将坩埚中残余物用水溶解 ,测定水溶液中的Ｈ+、ＮＨ+4、ＳＯ2 -4 等离子的含量。其中ＮＨ+4含量采用甲醛法测定 ,ＳＯ2 -4 含量采用硫酸钡重量法测定…     

Chain scission in polystyrene by impact fracture

The number of chain scissions n_s per unit fracture area by impact in high-molecular weight polystyrene is determined to be approximately 3.3 × 10¹⁴/cm² at room temperature. This is almost 20 times larger than would be expected if chain scissions took place only at, or very close to, fracture surfaces. This result was obtained by measuring the molecular weight decrease and the total fracture area of the impact fragments by using size exclusion chromatography and statistical particle size measurements, respectively. The large n_s strongly indicates that significant chain breakage occurs during crazing before the propagation of cracks. An average craze thickness before breakdown under impact is estimated from n_s to be around 2 μm. In a diluted polymer, n_s is found to be significantly lower than the extrapolated value, assuming a linear dilution of entangled chain crossings at the fracture surface. This low chain scission density, however, can be explained by taking into account the reduction of craze breakdown strain in the diluted polymers. Finally, the broken chain ends of polystyrene appear to be stable under ambient conditions. © 1992 John Wiley & Sons, Inc.     

On the properties of surfactant aqueous solutions

Summary From studies of aqueous solutions of dodecylammoniumnitrate an association mechanism has been proposed involving multiequilibrium. In the concentration range considered we can differentiate between two aspects: ranges of marked qualitative and quantitative changes and formation of differently structured surfactant species.

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Zusammenfassung Aus der Untersuchung wäßriger Lösungen von Dodecylammoniumnitrat würde ein Assoziationsmechanismus abgeleitet, welcher ein Multiequilibrium beinhaltet. Im untersuchten Konzentrationsbereich können zwei Bereiche unterschieden werden: Bereiche mit ausgeprägten qualitativen und quantitativen Änderungen und Bereiche mit der Bildung von verschieden strukturierten oberflächenaktiven Spezies.

     

Local order and shape of a polymer chain in an external electric field

A solution of polymer chains in the presence of an external electric field is considered. Dipole-like interactions between polymer chain segment-vectors and the electric field are assumed to be proportional to the cosine of the angle between the segment-vector and the direction of the electric field. Parameters characterizing the shape of the chain (i.e., the chain end-to-end distance and cross-section per chain), and parameters describing the local order at the segmental and chain level (i.e., moments of the first and second Legendre polynomials 〈P₁〉 and 〈P₂〉 are calculated. The optical anisotropy and the molecular shape change induced by the external electric field are discussed.     

Thermal decomposition kinetic of reactive solids based on isothermal calorimetry measurements

An isothermal method was applied to measure the thermal decomposition of reactive solids in a sensitive heat flux reaction calorimeter, C80. This technique experimentally clarified the decomposition mechanisms of unstable substances based on the shapes of the heat flow curves, from which autocatalysis, first-order reaction or pseudo-autocatalytic reaction could be recognized. Kinetic parameters were derived from the measured data.     

Kinetics of the thermal decomposition of dinitramide

The kinetic regularities of the heat release during the thermal decomposition of liquid NH₄N(NO₂)₂ at 102.4–138.9 °C were studied. Kinetic data for decomposition of different forms of dinitramide and the influence of water on the rate of decomposition of NH₄N(NO₂)₂ show that the contributions of the decomposition of N(NO₂)₂ ⁻ and HN(NO₂)₂ to the initial decomposition rate of the reaction at temperatures about 100 °C are approximately equal. The decomposition has an autocatalytic character. The analysis of the effect of additives of HNO₃ solutions and the dependence of the autocatalytic reaction rate constant on the gas volume in the system shows that the self-acceleration is due to an increase in the acidity of the NH₄N(NO₂)₂ melt owing to the accumulation of HNO₃ and the corresponding increase in the contribution of the HN(NO₂)₂ decomposition to the overall rate. The self-acceleration ceases due to the accumulation of NO₃ ⁻ ions decreasing the equilibrium concentration of HN(NO₂)₂ in the melt. For Part 2, see Ref. 1. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 3, pp. 395–401 March 1998.