Kinetics of the thermal decomposition of bis-pentafluorosulfur trioxide(SF5O3SF5) in the presence of carbon monoxide

The thermal decomposition of SF₅O₃SF₅ in the presence of CO has been investigated between -9.8°C and + 9.9°C. Besides traces of S₂F₁₀, equimolecular amounts of SF₅O₂SF₅ and CO₂ are formed. The reaction is homogeneous. Its rate is proportional to the pressure of the trioxide and in dependent of the total pressure, the pressure of inert gases and of carbon monoxide: where k = k_1∞ = 10^16.32±0.40 exp(?25,300 ± 500 cal)/RT sec^?1. Consequently, In the presence of oxygen a sensitized CO₂ formation is observed. A mechanism is given which explains the experimental results.     

The kinetics and the mechanism of the thermal reaction between sulfurtetrafluoride (SF4) and trifluoromethylhypofluorite (CF3OF)

The kinetics of the thermal reaction between SF₄, and CF₃OF has been studied between 142°C and 185°C. The reaction was found to be homogeneous and the only products formed are equimolecular amounts of SF₆ and CF₃O₂CF₃ and smaller amounts of CF₃OSF₅. The reaction mechanism was not affected by the total pressure, the oxygen pressure, or by the buildup of products. The experimental data can be explained by the following mechanism: The rate constants can be expressed as      

The kinetics and mechanism of thermal decomposition of alkyl isocyanates

The kinetics of the gas-phase decomposition of ethyl, isopropyl, and t-butyl isocyanates have been studied in the temperature range of 380–530°C. t-Butyl isocyanate decomposes almost exclusively by a unimolecular route to isobutene and HNCO, but in EtNCO and i-PrNCO this route competes with a free-radical chain which produces CO, CH₄, and HCN or CH₃CN. In i-PrNCO, however, the chain process is very rapidly inhibited by the propene formed in the parallel unimolecular route. A minor heterogeneous bimolecular decomposition in each case gives rise to carbon dioxide and a carbodiimide. Mechanisms and trends in the alkyl isocyanates from methyl through t-butyl are discussed.     

The kinetics and the mechanism of the thermal decomposition of bis(trifluoromethyl) trioxide. The influence of carbonmonoxide on its decomposition

The kinetics of the thermal decomposition of CF₃O₃CF₃ has been investigated in the pressure range of 15–599 torr at temperatures between 59.8 and 90.3°C and also in the presence of CO between 42 and 7°C. The reaction is homogeneous. In the absence of CO the only reaction products are CF₃O₂CF₃ and O₂. The rate of reaction is strictly proportional to the trioxide pressure, and is not affected by the total pressure, the presence of inert gases, and oxygen. The following mechanism explains the experimental results: In the presence of CO there appear CO₂, (CF₃OCO)₂, and CF₃O₂C(O)OCF₃ as products. With increasing temperature the amount of peroxicarbonate decreases, while the amounts of oxalate and CO₂ increase. The rate of decomposition of the trioxide above a limiting pressure of about 10 torr CO is strictly first order and independent of CO pressure, total pressure, and the pressure of the products. The addition of larger amounts of O₂ to the CO containing system chaqnges the course of the reaction.     

Solvent effect on the kinetics and mechanism of the thermal decomposition oftris-oxalactocobaltate(III) complex

Summary The kinetics of the thermal decomposition of thetris-oxalactocobaltate(III) complex has been investigated in the presence of EtOH and (CH₂OH)₂ spectrophotometrically in the 50–70 ± 0.1 ° C range. The rate of the reaction decreases upon the addition of either of the alcohols to the reaction medium, whereas the activation energy increases. The thermodynamic parameters were calculated and are discussed in terms of the solvation effects. The influence of the dielectric constants of the solvent mixtures on the rate has been studied. A free radical mechanism is proposed and discussed.     

Mechanism and kinetics of the thermal decomposition of 5-aminotetrazole

The kinetics of 5-aminotetrazole thermal decomposition in the condensed phase at high heating rates (∼100 K/s) was studied by the dynamic mass spectrometric thermal analysis using a molecular beam sampling system, and the product composition was determined. Two routes of 5-aminotetrazole decomposition were distinguished, one yielding HN₃ and NH₂CN (route 1), and the other N₂ and CH₃N₃ (route 2). The activation energy and rate constant of 5-AT decomposition were determined for each route.     

Studies on the thermal decomposition kinetics and mechanism of ammonium niobium oxalate

Ammonium niobium oxalate was prepared and characterized by elemental analysis, XRD and FTIR spectroscopy analysis, which confirmed that the molecular formula of the complex is NH₄(NbO(C₂O₄)₂(H₂O)₂)(H₂O)₃. Dynamic TG analysis under air was used to investigate the thermal decomposition process of synthetic ammonium niobium oxalate. It shows that the thermal decomposition occurs in three stages and the corresponding apparent activation energies were calculated with the Ozawa–Flynn–Wall and the Friedman methods. The most probable kinetic models of the first two steps decomposition of the complex have been estimated by Coats–Redfern integral and the Achar–Bridly–Sharp differential methods.     

Crystal structure and thermal decomposition mechanism of a 5-aminotetrazole copper(II) complex

A novel 5-aminotetrazole mixed ligands complex of formula [Cu(PTS)₂(ATZ)₂(H₂O)₂] (C₁₆H₂₄CuN₁₀O₈S₂, PTS = p-toluenesulfonate, ATZ = 5-aminotetrazole) has been obtained by the reaction of 5-aminotetrazole with copper acetate and p-toluenesulfonic acid on heating in water. It was characterized by elemental analysis, FT-IR spectroscopy, and X-ray single crystal diffraction. The compound crystallizes in monoclinic system, space group P2₁/c, Z = 2, a = 14.079(4) Å, b = 6.088(3) Å, c = 14.632(4) Å, β = 105.268(4)°, V = 1209.8(5) Å³. The central copper(II) cation is coordinated by two N atoms and four O atoms from two ATZ ligands, two water molecules and two p-toluenesulfonate ions to form a six-coordinated and distorted octahedral structure. Neutral ATZ is coordinated in the monodentate mode by the N(4) atom. The sulfonate group of the PTS ligand remains weak-coordinated modes and forms a number of hydrogen bonds with water molecule ligands and ATZ ligands. A supramolecular framework is connected by electrostatic interaction, weak coordinated bonding, hydrogen-bonding, and π–π interaction. The thermal decomposition mechanism of the title compound was predicted based on DSC, TG-DTG, and FT-IR analyses. Thermolysis of ATZ and its several derivatives is compared.     

Studies on kinetics and mechanism of initial thermal decomposition of nitrocellulose

The thermal decomposition of nitrocellulose (NC) 12.1% N, has been studied with regard to kinetics, mechanism, morphology and the gaseous products thereof, using thermogravimetry (TG), differential thermal analysis (DTA), IR spectroscopy, differential scanning calorimetry (DSC) and hot stage microscopy. The kinetics of the initial stage of thermolysis ofNC in condensed state has been investigated by isothermal high temperature infrared spectroscopy (IR). The decomposition ofNC in KBr matrix in the temperature range of 142–151°C shows rapid decrease in O?NO₂ band intensity, suggesting that the decomposition of NC occurs by the rupture of O?NO₂ bond. The energy of activation for this process has been determined with the help of Avrami-Erofe'ev equation (n=1) and is ≈188.35 kJ·mol^?1. Further, the IR spectra of the decomposition products in the initial stage of thermal decomposition ofNC, indicates the presence of mainly NO₂ gas and aldehyde.     

The kinetics and mechanism of induced thermal decomposition of peroxomonosulphate by phase transfer catalysts

The kinetics of induced decomposition of potassium peroxomonosulphate (PMS) by the phase transfer catalysts (PTC), viz. tetrabutylammonium chloride [TBAC] and tetrabutylphosphonium chloride [TBPC] have been investigated. The effect of [PMS], [PTC], ionic strength of the medium and temperature on the rate of decomposition of PMS was studied. The rate of decomposition of PMS was monitored under pseudo-first-order condition at a constant temperature (50 ± 0.1 °C). The rate of decomposition was first order with respect to PMS for TBAC and half order for TBPC. The order with respect of PTC was found to be unity for TBAC and half order for TBPC. A suitable kinetic scheme has been proposed to account for the experimental data and its significance is discussed.     

过氧化苯甲酸叔丁酯的热分解动力学研究及SADT推算

研究了过氧化苯甲酸叔丁酯的热分解动力学及不同包装规格下的自加速分解温度(SADT),利用C600微量热仪测试了过氧化苯甲酸叔丁酯的热分解特征,得到升温速率分别为0.1 K/min、0.2 K/min、0.5 K/min、1 K/min下热流随时间的变化曲线,并使用Friedman等转化率法对所得的实验数据进行分析处理,得到了过氧化苯甲酸叔丁酯的分解反应活化能、指前因子等热动力学参数,推算了不同包装规格的过氧化苯甲酸叔丁酯的SADT。结果表明TBPB分解活化能及指前因子随转化率变化而变化,活化能范围为42-135.5 kJ/mol,指前因子范围为0.25-33.5,在25L聚乙烯桶包装下的SADT为59℃,50L下为52℃,200L下为46℃。     

The kinetics and mechanism of the decomposition of N-chloroleucine

At 298 K the rate constant for the decomposition of N-chloroleucine has the constant value 3.20 × 10⁻⁴ s⁻¹ over the range pH 5–12, increases with increasing acidity at pH < 5, and increases with pH at pH > 12. A mechanism is put forward which explains these results.     

2-(4-甲氧羰基苯基)-5-硝基-6-羟基苯并噁唑的热分解机理及动力学

顺式聚对苯撑苯并二噁唑(cis-poly-paraphenyl enebenzobisoxazole,简称PBO)引起了人们的重视[1-3]。由PBO制得的高性能纤维的商品名为Zylon[2],Zylon不仅具有高的机械强度,而且具有高的热氧化稳定性[2,4-5]。PBO纤维和PBO复合材料在宇航、武器装备等领域中有广阔的应用前景[1-     

Mechanism and kinetics of thermal decomposition of nickel(II) sulfate(VI) hexahydrate

This work presents results of research on thermal decomposition of nickel(II) sulfate(VI) hexahydrate in air and in helium atmosphere. On the base of TG and XRD results a mechanism of thermal decomposition of NiSO₄ hydrate was established. For calculations of kinetic parameters of the Arrhenius equation, the Coats-Redfern approximation was applied. Choice of g(a) function and thus of a mechanism best describing given stage of decomposition was performed by testing 12 kinetic models. This revised version was published online in July 2006 with corrections to the Cover Date.     

The kinetics of thermal decomposition of bismuth oxohydroxolaurate

The bismuth salt of lauric (dodecanic) acidBi₆O₄(OH)₄(C₁₁H₂₃COO)₆ was studied earlier. This salt has layer structure (the interlaminardistance=37.50 Å), under heating this liquid-crystalline state has themesomorphic transformation, turns to the amorphous state, decomposes stepwisewith the formation of well-ordered layers of bismuth nanoparticles. DSC-curveswere used for the study of the decomposition kinetics in the area of decompositionwith small mass loss and exothermic effect (423–483 K).     

Experimental and theoretical study on the kinetics and mechanism of thermal decomposition of 1,2-dichloroethane

The kinetics and mechanism for the thermal decomposition of 1,2-dichloroethane (EDC) was studied in a flow system over the temperature range of 849–1064 K and pressure range of 10–300 Torr under homogeneous conditions in a tubular quartz reactor. Gas chromatography was used to measure the concentration of products. Four-center HCl elimination was found to be the most important channel in this system. Minor products such as methane, ethylene, acetylene, chloroethane, and chloroprene were identified. Ab initio calculations at the DFT, CASMP2, and QCISD(T) levels of theory were carried out to investigate the mechanism of this system and to calculate necessary parameters to compute the rate constants of different steps. Dependence of formation of vinyl chloride on the total pressure is measured, experimentally.     

Mechanisms and kinetics for the thermal decomposition of 2-azido-N,N-dimethylethanamine (DMAZ)

To gain insight into the mechanisms and kinetics of 2-azido-N,N-dimethylethanamine's (DMAZ's) thermal decomposition postulated reaction paths were simulated with ab initio and density functional theory quantum chemistry models. Four reaction types were modeled: (i) spin-allowed and spin-forbidden paths involving N-N(2) bond fission and nitrene formation, (ii) HN(3) elimination with the formation of (dimethylamino)ethylene, (iii) N-N(2) bond fission with the formation of molecules with three- or four-membered heterocyclic rings, and (iv) simple scission of C-H, C-N, and C-C bonds. The geometries of stationary points of the reactions were obtained with a MPWB1K/6-31+G(d,p) model. To locate and model the geometries of minimum energy intersystem crossing points for triplet nitrene formation and isomerization, unrestricted broken spin symmetry calculations were performed. Employed to model an analogous path for methyl azide's decomposition, this approach was found to yield results similar to those obtained with a CASSCF(10,8)/aug-cc-pVDZ model. Of the four reaction types studied, N-N(2) bond fissions with singlet or triplet nitrene formation were found to have the lowest barriers. Barriers for paths to cyclic products were found to be 2-4 kcal/mol higher. Kinetic rate expressions for individual paths were derived from the quantum chemistry results, and spin-allowed nitrene formation was found to be dominant at all temperatures and pressures examined. The expression 2.69 × 10(9) (s(-1))T(1.405) exp(-39.0 (kcal/mol)/RT), which was derived from QCISD(T)/6-31++G(3df,2p)//MPWB1K/6-31+G(d,p) results, was found to be representative of this reaction's gas-phase rate. Adjusted on the basis of results from self-consistent reaction field models to account for solvation by n-dodecane, the expression became 1.11 × 10(9) (s(-1))T(1.480) exp(-37.6 (kcal/mol)/RT). Utilizing this result and others derived in the study, a model of the decomposition of n-dodecane-solvated DMAZ was constructed, and it generated simulations that well-reproduce previously published measured data for the process.     

The decomposition mechanism of new solid-state 4(5)-aminoimidazole-5(4)-carboxamide coordination compounds

Imidazole ring coordination compounds are very useful models to better understand the coordination properties and the reaction mechanisms of biologically important systems. On the basis of previous work, new Co(II)-, Ni(II)- and Cu(II)-4(5)-aminoimidazole-5(4)-carboxamide coordination compounds have been synthesized and characterized by elemental analysis, UV-Vis and IR spectroscopies. Their thermal stability was determined by differential scanning calorimetry and by thermogravimetry, and the decomposition mechanisms were investigated by evolved gas analysis (EGA).     

The thermal decomposition of N,N-dimethyl-3-oxa-glutaramic acid and the kinetics of its second-stage thermal decomposition reaction

N,N-dimethyl-3-oxa-glutaramic acid was purified and characterized by 1H-NMR, Fourier transform in-frared spectroscopy (FT-IR) and elemental analysis. The thermal decomposition of the title compound was studied by means of thermogravimetry differential thermogravimetry (TG-DTG) and FT-IR. The ki-netic parameters of its second-stage decomposition reaction were calculated and the decomposition mechanism was discussed. The kinetic model function in a differential form, apparent activation energy and pre-exponential constant of the reaction are 3/2 [(1-α) 1/3-1]-1, 203.75 kJ-mol-1 and 1017.95s-1, respec-tively. The values of ΔS≠, ΔH≠ andΔG≠ of the reaction are 94.28 J-mol-1-K-1, 203.75 kJ-mol-1 and 155.75 kJ-mol-1, respectively.