A New Germanium Complex Containing Chelating Pyridinecarboxylate Ligands: cis‐Dihydroxybis(pyridine‐2‐carboxylato‐κN1,κO2)germanium Hydrate (1 : 2) (cis‐[Ge(pyca)2(OH)2]⋅2 H2O)

A new germanium complex, cis‐[Ge(pyca)₂(OH)₂]?2 H₂O ( 1 ; pyca=pyridine‐2‐carboxylato), was synthesized by the reaction of [Ge(acac)₂Cl₂] (acac=acetylacetonato=pentane‐2,4‐dionato) with potassium pyridine‐2‐carboxylate (Kpyca) in H₂O/THF. According to the single‐crystal X‐ray diffraction analysis, each Ge‐atom of 1 is coordinated by two pyca ligands and two OH^? groups (Fig. 1). These molecules are bonded to each other via a system of H‐bonds resulting in a sheet‐like structure (Fig. 2). The complex is decomposed during heating with stepwise mass loss and formation of GeO₂ as final product (Fig. 3).     

甲磺酸帕珠沙星的热分解机理及动力学

采用热重(TG)和差示扫描量热(DSC)法测定了甲磺酸帕珠沙星(PZFX)在氮气氛和空气氛中的热分解过程,测定了PZFX及其在热分解过程中不同阶段残余物的红外光谱,运用量子化学GAMESS软件计算了PZFX分子的键级,推断了PZFX的热分解机理.结果表明PZFX的热分解过程的起始步骤是甲磺酸的分解.采用Ozawa方法计...     

Thermal and kinetic evaluation of biodiesel derived from soybean oil and higuereta oil

The purpose of this work is to evaluate the thermal and kinetic behavior of biodiesel derived from soybean and higuereta oils. The thermogravimetric profiles of biodiesels indicated one step associated with decomposition of the ethyl esters. The thermal profiles were compared with reference diesel. Kinetic parameters were obtained by thermal analysis, estimating reaction order, pre-exponential factor and activation energy. For estimation of the kinetic parameters the Coats & Redfern method was used. The selection criterion of best fit was based on the correlation coefficient of the linear regression and the compensation effect of the kinetic parameters.     

三种2-羟基-1-萘醛酰腙的晶体结构、热分解及其与CT-DNA的相互作用

Three acyl hydrazones N'-((2-hydroxynaphthalen-1-yl)methylene)-2-phenylacetohydrazide (1), N'-((2-hydroxynaphthalen-1-yl) methylene)-2-(4-hydroxyphenyl)acetohydrazide hydrate (2), and N'-((2-hydroxynaphthalen-1-yl) methylene)-2-(2-methoxyphenyl) acetohydrazide hydrate (3) were synthesized and then characterized by elemental analysis and single-crystal X-ray diffraction. The crystallographic data indicated that both compounds 2 and 3 crystallized in the monoclinic crystal lattice, space group C2/c, while compound 1 crystallized in the orthorhombic space group Pbca. The thermal decomposition processes of the three hydrazones were studied by thermogravimetry. The thermal decomposition temperatures of compounds 1, 2, and 3 were 318.23, 319.04, and 323.01℃, respectively. Meanwhile, the apparent activation energies for thermal decomposition for compounds 1, 2, and 3 were 115.90, 145.18, and 129.38 kJ·mol^-1, respectively, calculated according to the Kissinger and Ozawa equations. The interactions of compounds 1-3 with calf thymus (CT)-DNA were evaluated by microcalorimetry. The results indicated these interactions were homogenous endothermic processes with non-identical interaction time (1.00-50.0 min) and interaction enthalpies (0.47-15.50 kJ·mol^-1). The interaction enthalpies of compounds 1 and 2 were higher than those of their precursors, while the interaction enthalpy of compound 3 was lower than that of its precursor.     

Thermal decomposition characteristics of Alder-ene adduct of diallyl bisphenol A novolac with bismaleimide: effect of stoichiometry, novolac molar mass and bismaleimide structure

The addition-cured blends of diallyl bisphenol A formaldehyde resin (ABPF) with various bismaleimides (BMIs) were evaluated for thermal stability and degradation behavior by thermogravimetric analysis (TGA). TGA of the blend of ABPF and 2,2-bis 4-[(4-maleimido phenoxy) phenyl] propane (BMIP) with varying maleimide to allylphenol stoichiometry indicated that the thermal stability of the system was only marginally improved by the increase in BMI stoichiometry in the blend. The effect of BMI structure on thermal stability was studied using four different BMIs, viz. bis (4-maleimido phenyl) methane (BMIM), bis (4-maleimido phenyl) ether (BMIE), bis (4-maleimido phenyl) sulfone (BMIS) and BMIP. TGA showed a two stage decomposition pattern for BMIS system and a single stage for all the other three. The thermograms of BMIM and BMIE were identical and superior to that of BMIS; the latter showing a relatively poor performance at lower temperatures. Compared to the BMI-adduct of monomeric diallyl bisphenol A (DABA), the polymeric analog viz. ABPF system exhibited better thermal stability. Non-isothermal kinetic analyses of the different systems showed the decomposition occurring in at least two kinetic steps. The computed activation energy exhibited a direct correlation to the relative thermal stability of the systems.     

Thermal Behavior of an Fe(III)‐2,9,16,23‐Tetramidephthalocyanine‐Grafted Poly(N‐Vinylcarbazole)

Abstract

The introduction of 2,9,16,23‐tetramide‐Fe(III)phthalocyanine [Fe(III)taPc] units into phosphorylated poly(N‐vinylcarbazole) yields an amorphous grafted polymer containing free carbazolyl groups, phosphonic acid attached to carbazolyl groups, and grafted Fe(III)taPc units as evidenced by infrared spectroscopy. Several thermal transitions were detected by differential scanning calorimetry (DSC). The thermodegradation of the grafted sample, analyzed by simultaneous thermogravimetry‐differential thermal analysis (TG‐DTA), showed successive endo‐ and exothermal reactions resulting from the development of a cross‐linked structure. To determine kinetic parameters, both isothermal and dynamic experiments were performed at the different steps of the degradation process and theoretical methods were applied.     

Synthesis,Crystal Structure Determination from X‐Ray Powder Diffractometry and Vibrational Spectroscopic Properties of Mg[N(CN)2]2 · 4 H2O

Magnesium dicyanamide tetrahydrate Mg[N(CN)₂]₂ · 4 H₂O was synthesized by aqueous ion exchange starting from Na[N(CN)₂] and Mg(NO₃)₂ · 6 H₂O. The crystal structure was solved and refined on the basis of powder X‐ray diffraction data (P2₁/c, Z = 2, a = 737.50(2), b = 732.17(1), c = 971.67(2) pm, β = 98.074(1)°, wR_p = 0.059, R_p = 0.046, R_F = 0.075). In the crystal there are neutral complexes [Mg[N(CN)₂]₂(H₂O)₄] which are only connected via hydrogen bonds. Above 40 °C the tetrahydrate decomposes into anhydrous Mg[N(CN)₂]₂.     

Thermogravimetric study of flame-retarding properties on phosphorylated beech sawdust

Beech sawdust (S) and samples containing 1% of H₃PO₄ (SP), (NaPO₃)_n (PS), P₂O₅ (POS), NaOH/P₂O₅ (SPS), NaOH (SS) or Na₂CO₃ (CS) were analysed using dynamic and isothermal thermogravimetry (TG) in nitrogen and oxygen environments. According to the results of dynamic experiments in nitrogen, the thermal resistance at 275 °C decreased in the order: S > SS > CS > SP> SPS > PS > POS, while in oxygen the order was: S > POS > SPS=CS=PS > SP > SS. The difference in residues obtained in nitrogen in comparison to oxygen environment reaches its maximum at temperatures from 300 to 325 °C and according to the decreasing values the following order could be listed: SS (300 °C/27%) > SP (325 °C/25%) > CS (300 °C/24%) > S (325 °C/23%) > SPS (300 °C/19%) > PS (300 °C/11%) > POS (275 °C/4%). This indicates that with a decreasing difference in residues formed in oxidative and inert environments the flame-retardant effect of the sample is increasing. The calculated initial rate constants of residue formation and gasification and the corresponding activation energies of the processes in nitrogen and oxygen from the isothermal experiments gave smaller values of rate constants for SPS than for S. For the SPS sample in comparison with S the activation energy of residue formation in nitrogen decreased while the three remaining values increased. The E_r* of PS in the oxygen is the biggest from all studied samples under the conditions used, while SPS gave the biggest E_g* in the oxygen environment. The phosphorus could be washed out with water from SP and SPS, while it remained in PS and POS. These last two samples also have the best flame-retarding properties according to TG analysis.     

强碱阴离子交换树脂合成及热稳定性能研究

氯甲基化聚苯乙烯树脂与不同的叔胺反应制备了含不同季铵基团的强碱树脂.将氯甲基化聚苯乙烯树脂进行硝化、溴化反应后,再用三甲胺进行季铵化制备了苯环上含有吸电子基团的强碱树脂,测定了所制备树脂在水中的热稳定性.结果表明,位阻较大的季铵表现出较高的热稳定性;硝化、溴化后的树脂热稳定性有一定改善;而热重分析表明苯环上引入吸电子取代基不利于提高碱基在高温下的稳定性.     

Thermogravimetric study of some crosslinked copolymers based on poly(acrylonitrile-co-divinylbenzene)

Copolymer networks based on acrylonitrile (AN)/divinylbenzene (DVB) have been investigated by thermogravimetric analysis (TG) to evaluate their thermal stability in nitrogen atmosphere. Thermal stability was determined from TG-DTG curves to investigate the influence of AN and DVB in the synthesis of copolymers on the copolymer thermal properties. The TG and DTG curves of copolymers clearly show two thermodegradation stages. The solid residues produced after thermodegradation stages were analyzed by FTIR and elemental analysis (CHN). The decomposition temperatures were dependent on amount of AN and DVB used as the crosslinking agent. The degradation temperatures of copolymers were influenced by the diluent system during their synthesis. FTIR analyses indicate that the cyclization of the polymer proceeds before any mass loss.