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.     

Thermal stability and decomposition of pharmaceutical compounds

Thermal analysis of fusion and decomposition processes were carried out on recently synthetized pharmaceutical compounds in order to establish thermal stability criteria. This study was carried out using thermogravimetry, TG, and differential scanning calorimetry, DSC. Degradation and fusion temperatures have been produced as thermal data with the aim of to study the thermal stability of the compounds. Relationship is found among stability and a series of effects of structure of the compounds. The compounds which present an amide functional group in the central molecule are more stable because they have a comparatively higher fusion and degradation temperature. In addition, the stability of this type of compounds depends on the position of the electrophilic substitution (in ortho, meta or para). Likewise, the groups linked to the aromatic ring with high electronic density give stability, and therefore are able to delocalize the charge in a greater spacial interval. Therefore, criteria for the selection of substituents have established that improve the stability of compounds     

Thermal stability and thermal decomposition of N-oxides

Kinetic manometric studies indicate that the first step in the thermal decomposition of a number of N-oxides is the formation of a cyclic activated complex. There is a correlation between the thermal stability of the compounds studied in the liquid phase and the charge on the oxygen atom of the N-oxide group calculated by the MPDP method. Autocatalysis of gas evolution from halogenopyridine N-oxides is explained by hydrogen halide autocatalysis. The limit of thermal stability for N-oxides is likely to be no greater than 270°C.Biisk Lyceum, Altai Region, Biisk 659302. Kazan' State Technological University, Kazan' 420015. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1573–1576, November, 1995. Original article submitted October 20, 1995.     

Formation and thermal decomposition of germanium nitroxy compounds

The formation of a previously unknown compound with the stoichiometry Li₃GeNO₂ was found during studies on the reactions of germanium dioxide with lithium nitride and of germanium oxynitride with lithium oxide.

---

Zusammenfassung Während Untersuchungen über die Reaktionsfähigkeit von Germaniumdioxid und Germaniumoxynitrid gegenüber Lithiumoxid wurde die Bildung einer bis dahin unbekannten Verbindung der stöchiometrischen Zusammensetzung Li₃GeNO₂ festgestellt.

---

, Li₃GeNO₂.

     

Formation and thermal decomposition of aluminium nitroxy compounds

During the reactions of lithium oxide with aluminium nitride, and of lithium nitride with aluminium oxide, the formation has been observed of a previously unknown compound, of composition Li₂AlNO. The course of its thermal decomposition has also been determined.

---

Zusammenfassung Es wurde das Auftreten einer bisher unbekannten Verbindung der Zusammensetzung LiAlNO bei den Reaktionen von Lithiumoxid mit Aluminiumnitrid und Lithiumnitrid mit Aluminiumoxid beobachtet. Der Verlauf der thermischen Zersetzung dieser Verbindung wurde bestimmt.

---

Li₂AlNO. .

     

Structure and thermal decomposition of ammonium metatungstate

The structure and morphology of ammonium metatungstate (AMT), (NH₄)₆[H₂W₁₂O₄₀]?4H₂O, and its thermal decomposition in air and nitrogen atmospheres were investigated by SEM, FTIR, XRD, and TG/DTA-MS. The cell parameters of the AMT sample were determined and refined with a full profile fit. The thermal decomposition of AMT involved several steps in inert atmosphere: (i) release of crystal water between 25 and 200 °C resulting in dehydrated AMT, (ii) formation of an amorphous phase between 200 and 380 °C, (iii) from which hexagonal WO₃ formed between 380 and 500 °C, and (iv) which then transformed into the more stable m-WO₃ between 500 and 600 °C. As a difference in air, the as-formed NH₃ ignited with an exothermic heat effect, and nitrous oxides formed as combustion products. The thermal behavior of AMT was similar to ammonium paratungstate (APT), (NH₄)₁₀[H₂W₁₂O₄₂]?4H₂O, the only main difference being the lack of dry NH₃ evolution between 170 and 240 °C in the case of AMT.     

Structure and stability of isoxazoline compounds

Structure of isoxazoline compounds formed via the reaction of alkyl-substituted benzonitrile oxides with ethylene was determined by X-ray diffraction method. Isoxazoline ring is flattened, the bond lengths in it depend slightly on the nature of substituents (CH₃, C₂H₅) and their position in the benzene ring and the angle of rotation relative to the isoxazoline ring. The connection N-O has a length 1.422 Å. Thermal decomposition of isoxazolines in a liquid phase (160–280°C) is accompanied by the release of acetaldehyde and aromatic nitrile. Both the structure of the cycle and its stability is practically independent of the structure of an aromatic substituent. The rate constant of the initial stage is characterized by the low significance of kinetic parameters, E = 104°8 kJ mol^?1 and log a(A/c) = 7.2±0.8. The results obtained are rationalized in terms of biradical mechanism of isoxazoline ring-opening that includes an efficient recombination of the biradical and its disappearance as a result of synchronous multi-center rearrangement with the release of acetaldehyde.     

Formation and thermal decomposition of silicon oxynitride compounds II

In studies on the reactions of silicon oxynitride, Si₂N₂O, with lithium oxide and of lithium metasilicate with lithium nitride, the formation of a previously unknown compound with stoichiometry Li₅SiNO₃ has been observed.

---

Zusammenfassung Eine bisher unbekannte Verbindung der Zusammensetzung Li₅SiNO₃ wurde bei Reaktionen von Siliciumoxynitrid (Si₂N₂O) mit Lithiumoxid und von Lithiummetasilikat mit Lithiumnitrid erhalten.

---

(Si₂N₂O) , Li₅SiNO₃.

     

Formation and thermal decomposition of silicon oxynitride compounds I

The existence of formerly unknown compounds of the type M ₃ ¹ SiNO₂, suggested in previous papers, has been confirmed in reactions of lithium and sodium oxides with silicon oxynitride, Si₂N₂O.     

Kinetic investigation on thermal decomposition of organophosphorous compounds

In this paper, the thermal behaviours of two organophosphorous compounds, N,N-dimethyl-N′,N′-diphenylphosphorodihydrazidic (NDD) and diphenyl amidophosphate (DPA), were studied by thermogravimetery (TG), differential thermal analysis (DTA) and differential scanning calorimetery (DSC) techniques under non-isothermal conditions. The results showed that NDD melts about 185 °C before it decomposes. NDD decomposition occurs in two continuous steps, in the 190–410 °C temperature range. First thermal degradation stage for NDD results a broad exothermic peak in the DTA curve that is continued with a small exothermic peak at the end of decomposition process. On the other hand, applying TG-DTA techniques indicates that DPA melts about 150 °C before it decomposes. This compound decomposes in the temperature range of 230 to 330 °C in two steps. These steps are endothermic and exothermic, respectively. Activation energy and pre-exponential factor for the first step of decomposition of each compound were found by means of Kissinger method and were verified by Ozawa–Flynn–Wall method. Activation energy obtained by Kissinger method for the first stage of NDD and DPA decompositions are 138 and 170 KJ mol⁻¹, respectively. Finally, the thermodynamic parameters (ΔG ^#, ΔH ^# and ΔS ^#) for first step decomposition of investigated organophosphorous were determined.     

Solubility and thermal stability of some amino-mellitate compounds

By reaction between the anion of mellitic acid (benzenehexacarboxylic acid) and some protonated linear polyamines (diethylenetriamine, triethylenetetramine, tetraethylene-pentamine, pentaethylenehexamine, spermidine, and spermine), fairly insoluble complexes have been obtained, with the general formula (amine)(x)(mellitate)H(6) (diethylenetriamine and spermidine, x=1; triethylenetetramine and spermine, x=0.75; tetraethylenepentamine, x=0.6 and 0.8; pentaethylenehexamine, x=0.5). K(s0) values for these complexes have been determined at I=0 mol dm(-3) and T=25 degrees C (logK(s0) ranges between -48.2 and -56.6). The solubility has been studied as a function of pH and of ionic strength. The thermal analysis, performed using air or argon flow, showed that all the solids behave in a similar way. In the range 20-120 degrees C the loss of hydration water occurs, and in the range 150-350 degrees C the first step of non oxidative decomposition takes place, with complete decomposition at 650 degrees C in air flow, whilst in argon flow the decomposition is still incomplete at 900 degrees C. Preliminary results of a parallel diffractometric study are also reported.     

Formation and thermal decomposition of phosphorus oxynitride compounds of magnesium

The formation of a previously unknown crystalline compound, Mg₃PN₃O, was found during studies on the reactions of phosphorus oxynitride and phosphorus pentoxide with magnesium nitride.

---

Zusammenfassung Bei der Untersuchung der Reaktion von Phosphoroxynitrid und Phosphorpentoxid mit Magnesiumnitrid wurde die Bildung der bis dahin unbekannten kristallinen Verbindung Mg₃PN₃O beobachtet.

---

Mg₃PN₃O.

     

Structure and thermal stability of aliphatic polyoxamides

A homologous series of aliphatic polyoxamides, nylon 122, 102, 82, and 62, were prepared by the bulk polycondensation of dialkyl oxalates with diamines. Infrared spectroscopy, x-ray diffraction, differential thermal analysis, thermogravimetric analysis, and gas chromatography were used to study the structure and thermal stability of these polyoxamides. From the fiber pattern of nylon 122, a structural repeat distance of 19.5 Å was measured. This was in close agreement with the expected value for an extended planar, zigzag chain conformation. With the exception of the expected decrease in the structural repeat distance along the chain axis resulting from the different number of methylene groups, nylons 122, 102, and 82 were isostructural. Nylon 62 appeared to pack in a similar manner to the other materials studied. However, there were differences in the diffraction pattern of this polymer; these may be indicative of a different chain conformation or of strain in the crystalline regions of the polymer. The infrared spectra indicate the presence of strong hydrogen bonding in all the polymers. Thermal analysis and pyrolysis data revealed catastrophic polymer degradation between 400 and 500°C in nitrogen, with appreciable homolytic cleavage of the oxamide group.     

Study of the thermal decomposition processes of clathrate compounds

The decompositions of the clathrate compounds [M(NCS)₂(4-MePy)₄]·nG (whereM=Mn, Co, Ni or Cd;G=4-methylpyridine (4-MePy), benzene or xylenes) were studied on a Q-derivatograph under quasi-equilibrium conditions and with linear heating. These clathrates can be divided into two groups, in which the loss of guest is either (I) accompanied by destruction of the host complex, or (II) occurs before decomposition of the host complex. Kinetic parameters were obtained.

---

Zusammenfassung Die Zersetzung von Clathrat-Verbindungen der Zusammensetzung [M(NCS)₂(4-MePy)₄]·nG (M=Mn, Co, Ni, Cd;G=4-Methylpyridin (4-MePy), Benzen, o-,m, p-Xylen) wurde mittels Q-Derivatograph unter Quasi-Gleichgewichtsbedingungen und bei linearer Aufheizung untersucht.Die studierten Clathrate lassen sich in zwei Gruppen einteilen, je nachdem ob die Abgabe des Gastmoleküls G entweder vor oder unter Gleichzeitiger Zerstörung des Wirtskomplexes erfolgt. Kinetische Parameter wurden ermittelt.

---

Q- [M(NCS)₂(4-MePy)₂]·nG, M , , , G — 4- , . , . .

     

Preparation and thermal stability of organometallosiloxanes and organometallic compounds

This study covers the results of synthesis and investigation of thermal stabilities of several organometallosiloxanes and organometal compounds containing Group IV elements. Investigations indicate, in general, that heat resistance is related to the dissociation energies of the M? O bonds, the number of organic groups connected to the metal atom, and the structure of the molecule as a whole. More specifically, the substitution of Ge? O and Sn? O bonds for some Si? O linkages in organosiloxanes produces a reduction in heat stability. The influence of the Ge? O bond to decrease the resistance of siloxanes is less than that of the Sn? O linkage; an increase in the number of Sn? O linkages producing a corresponding decrease in heat stability of the organosiloxane. The resistances of the germoxysiloxanes to heat degradation are less than that which would be expected from indications given by the relative stabilities of more simple organometallic compounds.     

Formation and thermal decomposition of silicon oxynitride compounds. Part III

The formation of a previously unknown compound with stoichiometry Li₆SiN₂O₂ was found during studies on the reactivity of Li₂SiN₂ with Li₂O, of SiO₂ with Li₃N and of Li₃SiNO₂ with Li₃N.

---

Zusammenfassung Die Bildung einer bisher unbekannten Verbindung der Stöchiometrie Li₆SiN₂O₂ wurde bei Untersuchungen der Reaktivität von Li₂SiN₂ mit LiO, von SiO₂ mit Li₃N und von Li₃SiNO₂ mit Li₃N beobachtet.

---

Li₆SiN₂O₂ Li₂SiN₂ , , Li₃SiNO₂ .

     

Comparison between Abel test stability and thermal decomposition behavior of nitrocellulose

Journal of Thermal Analysis and Calorimetry - Nitrocellulose (NC) is prone to spontaneous decomposition with exothermic heat release and thus is generally evaluated for stability during the storage...