Thermal decomposition reactions of 2-methyltetrahydrofuran hydroperoxide and peroxide

Conclusions A study was made of the thermal decomposition of the hydroperoxide and peroxide of 2-methyltetrahydrofuran in solution, the principal products were identified, and it was shown that the decomposition proceeds to a large degree with an opening of the tetrahydrofuran ring. A reaction mechanism was proposed.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2281–2285, October, 1973.     

Polymer reactions. IV. Thermal decomposition of polypropylene hydroperoxides

The thermal decomposition of polypropylene hydroperoxide (PPH) consists of two consecutive reactions. The initial, faster reaction has rates up to 60 times that of the slower process. The former is largely suppressed by the addition of an excess of 2,6-di-tert-butyl-p-cresol. The course of reaction is the same in either solid state or in solution. The results are consistent with an intramolecular radical-induced mechanism for the initial reaction. This faster reaction consumes about 70–95% of the total hydroperoxides. The decomposition of PPH yields a maximum of about 1.8 radicals. Samples prepared from crystalline and amorphous polypropylenes have identical decomposition kinetics.     

Polymer reactions. III. Structure of polypropylene hydroperoxide

Oxidation of polypropylene introduces hydroperoxide groups into the polymer. Infrared spectroscopy has determined that more than 90% of these groups are intramolecularly hydrogen bonded. The sequential lengths and sequence distributions of these neighboring hydroperoxides were estimated from the electronic spectra of the polyenes derived from the polypropylene hydroperoxide by two methods: (1) reduction, acetylation, and pyrolysis, and (2) reduction and dehydration. The results indicate that all the hydroperoxide groups are present in sequences of length two and greater. Intramolecular hydrogen abstraction during oxidation could account for the formation of these neighboring hydroperoxides.     

Thermal decomposition products of polyethylene

Decomposition products of polymers have been determined by many investigators, but the results are often conflicting because of difficulties in analyzing a large number of products. A comprehensive analysis of the volatile thermal decomposition products of high-density polyethylene has been made with the latest techniques in gas chromatography. The formation of products is explained on the basis of free-radical mechanism. The predominant process in the formation of volatiles appears to be intramolecular transfer of radicals, in which isomerization by a coiling mechanism plays an important role in determining the relative quantities of each product.     

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     

Thermal decomposition of azoisopropane. II. Secondary decomposition processes

The thermal decomposition of azoisopropane (AIP) was studied in the presence of various quantities of propylene in the temperature and pressure intervals 498–553 K and 3.33–5.33 kPa. The inhibition functions relating to formation of the products were determined; these proved a good basis for interpretation of the formation of the secondary decompositon products of AIP. The experimental data support the conception that the βμ radical—radical reaction occurs. The product of this is not stable; its decomposition is one of the sources of the secondary products. The ratio of the rate constants was determined for the following reactions:      

Thermal decomposition reactions of nickel(II) complexes under quasi-equilibrium conditions

The stoichiometry of thermal decomposition and thermal (thermodynamic) stability was studied for the Werner clathrates [Ni(4-Mepy)₄(NCS)₂]·G, whereG = benzene(I), toluene(II) andp-xylene(III). The loss of the volatile components occurs in five steps in compounds I and II and in four steps in the complex III. According to the quasi-equilibrium data the thermodynamic stability of these compounds can be ordered in the following sequence: I<II<III. The increasing host-guest interaction (larger positive band shift in the visible spectra) was accompanied by increasing in the quasi-equilibrium temperature (T _D) for the complexes under study.     

Thermal gas-phase decomposition of chloroethylenes. II. Vinyl chloride

The thermal gas-phase decomposition of vinyl chloride has been studied behind shock waves over the temperature range of 1350-1900°K and the density range of 7 × 10^?7-1.5 × 10^?3 mol/cm³ (at 1600°K) in mixtures of C₂H₃Cl highly diluted with argon. The ultraviolet absorption of C₂H₃C was recorded at 230 nm as a function of time. The decomposition proceeds via molecular elimination of HCl. The unimolecular dissociation rate is pressure dependent at all but the highest pressures applied. Application of modified HKRR theory results in the rate expression for the limiting high pressure rate constant, and in a collision efficiency of derived from the limiting low-pressure rate constant.     

Cumyl hydroperoxide decomposition under the action of group II metal compounds

Cumyl hydroperoxide decomposition in chlorobenzene in the presence of magnesium, zinc, cadmium, or mercury 2-ethylhexanoate has been investigated. It has been established and kinetically proved that the decomposition reaction is preceded by the formation of a hydroperoxide-catalyst complex. Thermodynamic parameters of this complexation have been determined. The catalytic activity of the salts correlates with the ionization potentials of the metals.     

Thermal decomposition of amide and imide derivatives of maleated polyethylene

The thermal decomposition behavior of six derivatives of maleated polyethylene was investigated by high‐resolution pyrolysis gas chromatography–mass spectrometry. The results revealed that substituents attached to maleated polyethylene as amides formed from secondary amines were significantly less stable than imides formed from primary amines. Morpholine amide and N‐methylaniline amide derivatives of maleated polyethylene underwent significant decomposition at 160 °C and substantial decomposition at 200 °C. In contrast, the imide derivatives of maleated polyethylene were stable for long periods of time at elevated temperatures. Following 2 min of heating, the first traces of decomposition were detected at 200 °C for the 2‐aminoanthrancene imide derivative, at 255 °C for the 2‐phenethylamine imide, and at 280 °C for the 9‐aminomethylphenanthrene imide. With the exception of the 9‐aminomethylphenanthrene imide, all other derivatives decomposed to form the corresponding amine as the single most significant volatile product. The most likely explanation for this result is that the polymer contained small amounts of succinamic acid that did not close to form the imide. We concluded that the imide was stable even to 315 °C and that the amine was lost from β‐carboxyamide groups present in the sample. In the 9‐aminomethylphenanthrene imide derivative, we observed no loss of amine. Instead, we observed an alternative fragmentation process yielding 9‐methyl phenanthrene. The dependence of the thermal stability of these various derivatives of maleated polyethylene has important implications for the design of reactive‐blending strategies for polyolefins with other functional polymers. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 730–740, 2000     

Thermolysis of polyethylene hydroperoxides in the melt. Part 9: Re-examination of the experimental kinetics of hydroperoxide decomposition

The experimental kinetics of decomposition of polyethylene hydroperoxides in the melt is re-examined. It is found that the rates determined are more accurate if only the “free” hydroperoxides are taken into account instead of the total hydroperoxides that include also the “associated” hydroperoxides. Then, decomposition of polyethylene hydroperoxides in the melt can be attributed unambiguously to a first-order reaction that is valid in the whole time range of the thermolysis experiments. Nevertheless, the first-order rate constant determined this way increases with the initial hydroperoxide concentration. This constitutes a significant difference with the first-order rate constants that are valid in low molecular mass chemistry and are independent of the initial concentration of the reacting species. It has already been concluded previously that this experimental first-order rate cannot be attributed to true monomolecular hydroperoxide decomposition. Hence, another or other reactions must be envisaged for the interpretation of the specific first-order decomposition of the hydroperoxides in polyethylene melts.     

Thermal decomposition of oxalates. Part 17. Thermal decomposition of manganese(II) oxalate in a nitrogen atmosphere

Comparative studies of the kinetics of the isothermal and nonisothermal dehydration and decomposition of manganese(II) oxalate in an atmosphere of nitrogen are reported. Agreement between the values of the energy of activation for the isothermal and the nonisothermal dehydration at high heating rates was obtained. At low heating rate, the value obtained for the energy of activation is comparable with the enthalpy of dehydration. Values of 143 and 242 kJ mole^?1 were obtained for the energy of activation of the isothermal and nonisothermal decomposition, respectively. The difference is attributed to the condition of the anhydrous salt used in both cases. The theory of absolute reaction rate is applied and the parameters obtained are discussed.     

Heterogeneous reactions of polyethylene. II. Distortion of crystallites due to chlorination

The effect of heterogeneous chlorination of high-density polyethylene on its crystalline regions was investigated by NMR, x-ray diffraction, differential scanning calorimetry, and infrared spectroscopy. Crystallites remained inaccessible to attack by chlorine, even after extensive chlorination, however, their perfection was affected by extensive chlorination of the adjacent amorphous regions.     

Thermal decomposition reactions of amminecobalt(III)complexes

Simultaneous TG-DTG-DTA studies under non-isothermal conditions on [Co(NH₃)₆]Cl₃, [Co(NH₃)₅]Cl₂ and [Co(NH₃)]₂(C₂O₄)₃.4H₂O complexes have been carried out in air and argon atmospheres in the temperature range 293–1273 K. All the dissociation processes occur in three main stages. The kinetics of thermal decomposition of the complexes have been evaluated from the dynamic weight loss data, to determine the most probably mechanisms of the stages on the basis of statistical analysis. The decomposition of the compounds was controlled by diffusion and phase boundary reactions except stage III of the oxalate complex in argon (random nucleation). The activation energiesE _a of the particular stages of the thermal decomposition were calculated.

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Zusammenfassung Simultane TG-DTG-DTA-Untersuchungen an den Komplexverbindungen [Co(NH₃)₆]Cl₃, [Co(NH₃)₅Cl]Cl₂ und [Co(NH₃)₆]₂(C₂O₄)₃.4H₂O unter nichtisothermen Bedingungen wurden in Luft und Argonatmosphäre bei 293–1273 K durchgeführt. Die Zersetzung läuft in jeweils drei Stufen ab. Für die kinetische Auswertung der thermischen Zersetzung der Komplexverbindungen aus den dynamischen Gewichtsabnahmekurven wurde der wahrscheinlichste Mechanismus der einzelnen Stufen mit Hilfe von statistischen Analysen ermittelt. Die Zersetzung der Komplexverbindungen wird meist durch Diffusions- und Phasengrenzreaktionen kontrolliert, nur bei der 3. Stufe des Oxalatkomplexes in Argon herrscht statistische Keimbildung. Die AktivierungsenergienE _a der einzelnen Zersetzungsstufen werden berechnet.

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293–1273 — [Co(NH₃)₆]Cl₃, [Co(NH₃)₅Cl]G₂ [Co(NH₃)₆]₂(C₂O₄)₃.4H₂O. . , . , III , . _a .

     

Thermocatalytic decomposition of 1-methylcyclohexyl hydroperoxide

A mathematical model of a multistage process of thermocatalytic decomposition of 1-methyl-cyclohexyl hydroperoxide in the presence of sodium stearate is developed. A procedure for calculating the unknown rate and equilibrium constants of the elementary and overall reaction stages is described. It is based on an analysis of the kinetic relationships in consumption of the initial products and accumulation of the intermediate and final products of thermocatalytic decomposition, with account of the known constants for individual stages.Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 12, 2004, pp. 2003–2010.Original Russian Text Copyright © 2004 by Syroezhko, Begak.     

Thermal decomposition of Cu(II) adipate

The kinetics of isothermal decomposition of Cu(CH₂CH₂COO)₂ were studied at 483–503 K. The end-product was identified as CuO by X-ray diffraction and chemical analysis. The kinetics follow the Prout-Tompkins equation with an activation energy of 191 ± 10 kJ/moIe. The activation energies and the order of reaction were also evaluated from analysis of the DTG, DTA and TG curves of the sample.     

Thermal decomposition of copper(II) benzenedicarboxylates

The conditions and products of thermal decomposition of copper(II) benzenedicarboxylates in air atmosphere were studied at heating rates of 10 and 5 deg · min^–1. At a heating rate of 10 deg · min^–1, the o- and p-phthalate of copper(II) lose the crystallization water in two steps and the anhydrous complexes then decompose directly to CuO. Copper(II) m-phthalate loses crystallization water in one step to give the dihydrate, which then decomposes directly to CuO. When heated at 5 deg · min^–1 the m- and p-phthalates of copper(II) decompose in the same way, whereas the anhydrous o-phthalate decomposes to CuO through Cu₂O.

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Zusammenfassung Die Umstände und Produkte der thermischen Zersetzung von Kupfer(II)-benzoldicarboxylaten wurden in Luftatmosphäre bei einer Aufheizgeschwindigkeit von 10 bzw. 5 grd/min untersucht. Bei einer Aufheizgeschwindigkeit von 10 grd/min geben Kupfer(II)-o- und pphthalat ihr Kristallwasser in zwei Stufen ab, die wasserfreien Komplexe zerfallen anschliessend unmittelbar zu CuO. Kupfer(II)-m-phthalate geben Kristallwasser in einem Schritt ab und bilden dabei ein Dihydrat, was anschliessend direkt zu CuO zerfällt. Bei einer Aufheizgeschwindigkeit von 5 grd/min zeigt das m- und p-Phthalat des Kupfers(II) die gleichen Zersetzungserscheinungen, wogegen wasserfreies o-Phthalat sich zu CuO über die Zwischenstufe Cu₂O zersetzt.

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10 5 . 10 - - , . - , , . 5 - - , - .

     

Thermal decomposition of barium(II) tetraphenylborate

Barium(II) tetraphenylborate, Ba(Bph₄))₂·4H₂O was prepared, and its decomposition mechanism was studied by means of TG and DTA. The products of thermal decomposition were examined by means of gas chromatography and chemical methods. A kinetic analysis of the first stage of thermal decomposition was made on the basis of TG and DTG curves and kinetic parameters were obtained from an analysis of the TG and DTG curves using integral and differential methods. The most probable kinetic function was suggested by comparison of kinetic parameters. A mathematical expression was derived for the kinetic compensation effect.