Influence of secondary ligand on structures and topologies of lanthanide coordination polymers with 1,3,5-triazine-2,4,6-triamine hexaacetic acid

A series of new lanthanide coordination polymers has been synthesized and structurally characterized; [Ln₄(TTHA)₂(pzac)(H₃O)₂(H₂O)]·5H₂O (Ln = Pr (1a) and Nd (1b)), [Sm₈(TTHA)₄(pzac)_0.5(H₃O)(H₂O)_7.5]·4H₂O (2), [Ln₄(HTTHA)₂(SO₄)(H₂O)₄]·5H₂O (Ln = Pr (3a) and Nd (3b)), where H₆TTHA = 1,3,5-triazine-2,4,6-triamine hexaacetic acid, and H₂pzac = 2,5-dioxo-piperazine-1,4-diacetic acid. The compounds feature 3-D frameworks comprising the deprotonated H₆TTHA as the primary ligand and either the in situ generated pzac^2? or sulfate as the secondary ligands. The influence of the deprotonated H₆TTHA in directing the framework structures through preferential coordination modes and molecular conformation is described. The effect of the secondary ligands in increasing the compactness of the frameworks and in the alternation of the framework topologies based on the four-connected pts type is described.     

Efficient solid-phase synthesis of 1,3,5-trisubstituted 1,3,5-triazine-2,4,6-triones

The solid-phase synthesis of 1,3-disubstituted and 1,3,5-trisubstituted 1,3,5-triazine-2,4,6-triones from MBHA and Wang resin is described. Reaction of resin-bound amino acids with isocyanates yield resin-bound ureas, which further react with chlorocarbonyl isocyanate in toluene at 65 degrees C to selectively afford the resin-bound 1,3-disubstituted 1,3,5-triazine-2,4,6-triones. Selective alkylation at the N-5 position of the resin-bound 1,3-disubstituted 1,3,5-triazine-2,4,6-triones was accomplished by treatment with alkyl halides in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU). The desired products were cleaved from their solid support and obtained in good yield and purity. The method can be employed in production of toltrazuril analogue libraries for identification of new anticoccidial agents.     

Kinetic analysis of complex decomposition reactions using evolved gas analysis

For complex decomposition reactions, traditional methods, such as TG and DSC cannot fully resolve all of the steps in the reaction. Evolved gas analysis (EGA) offers another tool to provide more information about the decomposition mechanism. The decomposition of sodium bicarbonate was studied by TG, DSC and EGA using a simultaneous thermal analysis unit coupled to a FTIR. The decomposition of sodium bicarbonate involves two reaction products H₂O and CO₂, which are not evident from either TG or DSC measurements alone. A comparison of the reaction kinetics from TG, DTG and EGA data were compared.     

Thermal analysis and kinetic study of decomposition processes of some pesticides

The thermal analysis of some pesticides using simultaneous TG-DSC measurements and kinetic calculations by the dynamic TG technique have been carried out.With this technique it was attempted to group compounds with similar structures according to the shape and number of peaks of their thermoanalytical curves and to characterize their features by means of thermodynamic and kinetic quantities.Small variations in the structure of the components of a class make larger variations in the thermodynamic and kinetic values being in close agreement with the observed differences in their biological behaviour.

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Zusammenfassung Mittels simultanen TG-DSC-Messungen und kinetischen Berechnungen bei der DTG-Technik wurde eine thermische Analyse einiger Pestizide durchgeführt.Mit dieser Methode wurde versucht, Verbindungen mit ähnlichen Strukturen anhand der Form und Anzahl von Peaks ihrer thermoanalytischen Kurven zu gruppieren und ihre Eigenschaften mittels thermodynamischen und kinetischen Mengen zu charakterisieren.Geringe Änderungen in der Struktur der Komponenten einer Klasse verursachen größere Veränderungen der thermodynamischen und kinetischen Größen, was in enger Übereinstimmung mit den beobachteten Unterschieden ihrer biologischen Aktivität steht.

     

Thermal analysis/evolved gas analysis using single photon ionization

A simultaneous thermogravimetry/differential scanning calorimetry device (STA) was coupled to single photon ionization time of flight mass spectrometry (SPI-TOFMS) for evolved gas analysis (EGA). Thermal resolution with thermogravimetric signals (TG/DTG) is delivered by STA. On-line coupled EGA with SPI-TOFMS retains the thermal information from the STA and substantiates these with correlating mass spectra. The application of vacuum ultraviolet (VUV)-photons (8–12 eV) for soft ionization, allows almost fragment-free ionization. Thus, it becomes possible to interpret mass spectra of complex matrices, like natural products evolving simultaneously several molecules, without an additional separation step. The STA–SPI-TOFMS on-line coupling offers the possibility to track subset mass traces during one STA run. Focusing on material-depended mass traces, differentiation of organic matrices is obvious. In this work two types of research cigarettes, 3R4F and CM6 were used. While the 3R4F cigarette is composed of a blend of different tobacco sorts and different curing methods, the CM6 research cigarette consists of pure flue cured tobacco. The advantages of coupling on-line chemical analysis methods to thermal analysis (TA) are in the context of the achieved thermo-molecular signatures.     

Thermal decomposition of N-2,4,6-tetranitro-N-methylaniline

Purity determination by calorimetry has been used to determine the rate constant of thermal decomposition of N-2,4,6-tetranitro-N-methylaniline in liquid and solid states. The ratios of the initial rates of decomposition in solid and liquid decrease when temperature increases in the region not far below the melting point. The predicted rate constants in solid state are about 10 times greater than the one estimated by Wiseman. The thermal decomposition process at lower temperatures has been used to determine the rate constant in the decay phase. Activation energy and pre-exponential factor are also presented.     

First-principles study of crystalline mono-amino-2,4,6-trinitrobenzene, 1,3-diamino-2,4,6-trinitrobenzene, and 1,3,5-triamino-2,4,6-trinitrobenzene

The electronic structure and thermodynamic properties of crystalline mono-amino-2,4,6-trinitrobenzene (MATB), 1,3-diamino-2,4,6-trinitrobenzene (DATB), and 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) have been comparatively studied using density functional theory in the local density approximation. An analysis of electronic structure shows that the CNO₂ bonds in the three solids are easier to be broken in the thermal decomposition than the CNH₂ bonds. The calculated thermodynamic properties show that the order of their thermodynamic stability is TATB > DATB > MATB and their decomposition reactions are favorable under high temperature. Finally, an attempt is made to correlate the impact sensitivity of the three solids with their band gap. The result shows that there is the relationship between the band gap and impact sensitivity.     

Reaction of DMSO with ureas- a one step route to 1,3,5-tris(methylthiomethyl)-1,3,5-triazine-2,4,6-trione

Chemistry of Heterocyclic Compounds -     

A new simple synthesis of 3,5-disubstituted 1-amino-1,3,5-triazine-2,4,6-triones from ethoxycarbonylhydrazones and isocyanates

The 3,5-disubstituted 1-amino-1,3,5-triazine-2,4,6-triones were synthesized in good yields from aromatic aldehyde or ketone ethoxycarbonylhydrazones by treatment with aryl or methyl isocyanates in boiling triethylamine followed by hydrolysis with hydrochloric acid solution.     

Thermogravimetric study of polyacrylamide with evolved gas analysis

Dried samples of polyacrylamide in an He atmosphere have been subjected to thermogravimetric analysis in the 30–600°C range, and the evolved gases were monitored by FTIR. Water, ammonia, and small quantities of carbon dioxide are released in the first stages of decomposition (220–340°C), where the polymer chains remain intact and the reaction occurs on the pendant amide groups. In the second stage of decomposition (340–440°C), the majority of the weight loss occurs, and main chain breakdown occurs, releasing carbon dioxide, water, nitrile compounds, and imides. Trapping of the gases in this stage and analysis by GC–FTIR and GC–MS reveals the presence of more than 20 decomposition products, and confirms that a large proportion of these can be assigned to glutarimide and its substituted analogs. Imidization and dehydration reactions on the amide groups, as well as free radical breakdown of the main chains, with inter- and intramolecular hydrogen transfer, can account for many of the products of the decomposition. © 1993 John Wiley & Sons, Inc.     

Determination of mechanism of thermal decomposition of Mg,Ca and Zn hydrazidocarbonates by evolved gas analysis

Hydrazo-carbonates are complex compounds and products of the reactions between solutions of metal ion and solutions of hydrazido-carbonic acid. The decomposition of Mg(N₂H₃COO)₂. 2H₂O, Ca(N₂H₃COO)₂·H₂O and Zn(N₂H₃COO)₂ in inert atmosphere were studied. By classical thermoanalytical methods and data on the composition of the intermediates and final products the mechanisms of the thermal decomposition could not be resolved therefore also evolved gas analysis was used (EGA). The first step of thermal decomposition of Ca and Mg hydrazidocarbonates is dehydration. With the heating the decomposition of the hydrazido-carbonates proceeds under evolution of the ammonia, carbon monoxide and/or nitrogen and carbon dioxide giving as the intermediates for calcium and magnesium compounds the corresponding carbonates oxides as the final products. The zinc compound decomposes to the oxide, ZnO but also zinc cyanamide was detected during to the thermal treatment.     

Thermal characterization and isothermal kinetic analysis of commercial Creosote decomposition process

Isothermal decomposition process of commercial Creosote was analyzed by thermogravimetric technique in a nitrogen atmosphere, at four different operating temperatures (T = 230, 250, 270, and 290 °C). It was found that the two-parameter autocatalytic ?esták–Berggren kinetic model best describes the investigated process. It was established that the applied logistic function can successfully perform a given kinetic predictions of investigated process, at all operating temperatures. The experimental density distribution function of the apparent activation energy values was evaluated. Based of the characteristic shape of distribution curve, it was concluded that the isothermal pyrolysis of commercial Creosote represent a complex process, which probably includes primary and secondary (autocatalytic) pyrolysis reactions, together with various decomposition reactions and radicals recombination pathways.     

Thermal unimolecular decomposition mechanism of 2,4,6-trinitrotoluene: a first-principles DFT study

Simple C–NO₂ homolysis, 4,6-dinitroanthranil (DNAt) production by dehydration, and the nitro-nitrite rearrangement–homolysis for gas-phase TNT decomposition were recently studied by Cohen et al. (J Phys Chem A 111:11074, 2007), based on DFT calculations. Apart from those three pathways, other possible initiation processes were suggested in this study, i.e., CH₃ removal, O elimination, H escape, OH removal, HONO elimination, and nitro oxidizing adjacent backbone carbon atom. The intermediate, 3,5-dinitro-2(or 4)-methyl phenoxy, is more favor to decompose into CO and 3,5-dinitro-2(or 4)-methyl-cyclopentadienyl than to loss NO following nitro-nitrite rearrangement. Below ~1,335 K, TNT condensing to DNAt by dehydration is kinetically the most favor process, and the formations of substituted phenoxy and following cyclopentadienyl include minor contribution. Above ~1,335 K, simple C–NO₂ homolysis kinetically dominates TNT decomposition; while the secondary process changes from DNAt production to CH₃ removal above ~2,112 K; DNAt condensed from TNT by dehydration yields to that by sequential losses of OH and H above ~1,481 K and to nitro-nitrite rearrangement–fragmentation above ~1,778 K; O elimination replaces DNAt production above ~2,491 K, playing the third role in TNT decomposition; H escaping directly from TNT thrives in higher temperature (above ~2,812 K), as the fourth largest process. The kinetic analysis indicates that CH₃ removal, O elimination, and H escape paths are accessible at the suggested TNT detonation time (~100–200 fs), besides C–NO₂ homolysis. HONO elimination and nitro oxidizing adjacent backbone carbon atom paths are negligible at all temperatures. The calculations also demonstrated that some important species observed by Rogers and Dacons et al. are thermodynamically the most favor products at all temperatures, possibly stemmed from the intermediates including 4,6-dinitro-2-nitroso-benzyl alcohol, 3,5-dinitroanline, 2,6-dinitroso-4-nitro-phenylaldehyde, 3,5-dinitro-1-nitrosobenzene, 3,5-dinitroso-1-nitrobenzene, and nitrobenzene. All transition states, intermediates, and products have been indentified, the structures, vibrational frequencies, and energies of them were verified at the uB3LYP/6-311++G(d,p) level. Our calculated energies have mean unsigned errors in barrier heights of 3.4–4.2 kcal/mol (Lynch and Truhlar in J Phys Chem A 105:2936, 2001), and frequencies have the recommended scaling factors for the B3-LYP/6-311+G(d,p) method (Andersson and Uvdal in J Phys Chem A 109:2937, 2005; Merrick et al. in J Phys Chem A 111:11683, 2007). All calculations corroborate highly with the previous experimental and theoretical results, clarifying some pertinent questions.     

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.     

Thermal decomposition of 2,4,6-triazidopyrimidine in the melt

Russian Chemical Bulletin - The kinetics and the products of thermal decomposition of 2,4,6-triazidopyrimidine in the melt were investigated by thermogravimetry, manometry, mass-spectrometry, and...     

Ultrafast shock compression and shock-induced decomposition of 1,3,5-triamino-2,4,6-trinitrobenzene subjected to a subnanosecond-duration shock: an analysis of decomposition products

Shock compression studies of pressed and confined ultrafine 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) powder were conducted using ultrashort ~300 ps, ~50 GPa shock waves. The recovered decomposition products were characterized using X-ray photoelectron spectroscopy, infrared spectroscopy, and Raman spectroscopy. A substantial amount of shock-related chemistry was observed. Approximately 75% of the nitrogen atoms were liberated as gas-phase species, along with ~33% of the oxygen atoms, as a result of the applied shock. Furthermore, we observe C 1s binding energies suggesting the formation of sp(3) hybridized amorphous carbon. For comparison, a carbon nitride material was also prepared and characterized by thermally pyrolizing TATB. The shock-compressed TATB and the thermally pyrolized TATB are qualitatively different, suggesting that, carbon nitrides, a possible indicator of nitrogen-rich heterocycles precursors, are not a major product class for strongly overdriven shock conditions. These experimental conditions were, however, not detonation conditions, and the possible formation of nitrogen-rich heterocycles in actual detonations still exists.     

Insertion of Ethyl Isocyanate at the Tungsten–Chlorine Bond. Crystal Structure of 1,3,5-Triethyl-1,3,5-triazine-2,4,6-(1H,3H,5H)-trione

The reaction of tungsten hexachloride with excess ethyl isocyanate in dichloroethane leads to the insertion of three ligand molecules at one of the tungsten–chlorine bonds. The data of elemental analysis and IR spectroscopy confirm that the thermolysis of the reaction mixture affords the WCl₄(L₃Cl) complex (I), where L = –N(Et)C(O)–. The structure of the chain of inserted molecules in I is established on the basis of IR and NMR data, and the results of X-ray diffraction analysis of crystals of an organic product (II) of the hydrolysis of I. According to the latter, compound (II) is a derivative of s-triazine—1,3,5-triethyl-1,3,5-triazine-2,4,6-(1H,3H,5H)-trione.