含能化合物合成中典型反应过程的热效应

分别以尿素硝化制备二硝基脲、DATF氧化制备DNTF、DINA叠氮化制备叠氮硝胺工艺为研究对象,利用反应量热仪实验测定了三种典型单元反应过程的热量释放数据。结果表明,尿素硝化反应放热量为1.63kJ·g-1(以尿素计),最大放热速率为174.7 W;DATF氧化反应放热量为2.26 kJ·g-1(以DATF计),最大放热速率为64.7 W;DINA叠氮化反应放热量为0.88 kJ·g-1(以NaN3计),最大放热速率为90.1 W,同时获得各反应过程中的物料传热系数与比热容随时间变化曲线,为工艺设计与过程安全性研究提供理论依据。     

Methyltrioxorhenium catalyzed aerobic oxidation of organonitrogen compounds

A variety of tertiary, secondary and primary organonitrogen compounds have been efficiently and selectivity oxidized to their corresponding N-oxides, nitrones, and nitro compounds with molecular oxygen using methyltrioxorhenium as catalyst.     

Oxidation of diazo compounds by triphenyl phosphite ozonide. Quenching of singlet oxygen by diazo compounds

The reaction of triphenyl phosphite ozonide with various types of diazo compounds results in their oxidation, which is accomplished by singlet oxygen (¹O₂) evolved during thermal decomposition of the ozonide. A decrease in the ionization potential of the substrate results in an increase in the overall rate constant of quenching of¹O₂. In the case of 9-diazofluorene, the main channel of¹O₂ quenching is physical quenching.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1567–1571, September, 1994.The work was carried out with the financial support of the Russian Foundation for Basic Research (Project No. 93-03-5231).     

Estimation of the energetic nonhomogeneity of the surface of oxide and carbon materials

The molecular statistical method for evaluating the distribution of active sites of various adsorbents relative to their energies has been improved. This method is used not only for the treatment of experimental data on the adsorption of hydrocarbons on various adsorbents, which is the usual procedure, but also data on the adsorption of polar water and methanol molecules on the active sites of adsorbent surfaces. Two types of active sites differing in energy have been shown to exist on the surface of graphitized carbon black, the complex shungite carbon/mineral adsorbent, and modified Silochrom. Chromatographic, calorimetric, and structural adsorption data were used to establish the relationship between the observed maxima of the energy distribution function of the adsorption sites with concrete adsorption sites or pores of the surface, on which the molecules are adsorbed. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 44, No. 5, pp. 315–320, September–October, 2008.     

Microdetermination of oxygen in organic compounds using a glassy carbon pyrolysis tube and nondispersive infrared detection

A glassy carbon pyrolysis tube holding a filling of carbon granules, protected from atmospheric oxygen by the carrier gas and an aluminum oxide ceramic mantle tube, has been successfully used for the first time in the microdetermination of oxygen. The reaction temperature of 1300 °C assures the quantitative transformation of oxygen to carbon monoxide, which is measured by infrared detection. The analysis of fluorine, phosphorus and alkali metal containing compounds is now possible. A 10% hydrogen content in the nitrogen carrier gas enhances liberation of oxygen in organometallic compounds. The method is applicable to sample weights between 0.1 and 5 mg and the time required for one analysis is 100 s.     

Oxidation of thiol compounds by molecular oxygen in aqueous solutions

Side self-oxidation of thiols was studied. It was found that these reactions in neutral and alkaline solutions are induced by impurities of variable-valence metals. The ability of transition metals to catalyze oxidation of thiols changes in the order Cu > Mn > Fe > Ni Co. The plot of the self-oxidation rate vs. pH passes through a maximum whose position on the pH scale depends on both the nature of metal and the structure of the thiol oxidized. For thiols having different structures, the kinetic orders in reactions catalyzed by copper ions differently vary with pH, which is apparently associated with the formation of complexes possessing different catalytic activity.     

The reactivity of tributyltin oxygen compounds with CCl4: Implications for its use as an extraction/reaction solvent

A variety of tributyltin oxygen compounds,(nC₄H₉)₃SnOX where X = Sn(nC₄H₉)₃, C₂H₅, nC₄H₉, C₈H₁₇, CH₂C₆H₅, COCH₃, have been studied in refluxing CCI₄. A reaction was observed to occur where X = C₂H₅, C₄H₉, C₈H₁₇, CH₂C₆H₅, leading to the formation of (nC₄H₉)₃SnCl, CHCl₃ and an aldehyde. Possible reaction pathways are suggested. These reactions have implications for the use of CCl₄ as an extraction/reaction solvent.     

Predictions of compounds in the family of delafossites

This paper reports the results of our crystal-chemical analysis of structures from the delafossite family A⁺B³⁺X₂, where A and B are cations, and is oxygen. The family is represented by structures of two types, CuFeO₂ and α-NaFeO₂ (R \(\bar 3\) m, Z = 1). Predictions of new compounds are presented. About a hundred new crystals can be synthesized.     

New unsymmetrical difluoroaromatic compounds and estimation of their reactivities in nucleophilic substitution

A series of previously unknown unsymmetrical difluoroaromatic compounds, viz., p-fluorobenzoylphenyl(p-fluorophenyl)-substituted imidazoles, pyrazines, and quinoxalines, were synthesized according to multistep procedures with the use of chloral as the key compound. The reactivities of the resulting difluoroaromatic compounds were estimated based on ¹⁹F and ¹³C NMR spectral data and the results of quantum-chemical calculations. The calculated charge densities on the C_ipso atoms correlate linearly with the experimental chemical shifts in the ¹⁹F and ¹³C NMR spectra. Difluoroaromatic compounds, which are characterized by _F > –110 and _C > 163 and by the charge density on the C_ipso atom higher than 0.08 e, are sufficiently activated to be used for the preparation of high-molecular-weight polyethers.     

Effect of the structural disorder of T-shaped triazolyl-based coordination network compounds on the pore size and stability

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Temperature dependence of the transfer coefficient. The reduction of iodate in alkaline media

The reduction of iodate on a dropping mercury electrode was studied over a wide range of temperatures, and compared with earlier studies on the reduction of bromate under nearly identical conditions. A fully computerized experimental setup was used. This allows collection of a large number of experimental points, for proper statistical analysis of the data. The transfer coefficient was found to be a function of temperature, decreasing by about 10% with increasing temperature over 80°C. This behavior is very different from that found earlier for the reduction of bromate, where α is strictly independent of temperature.The reduction of iodate occurs at less negative potentials than that of bromate, far from interference by solvent decomposition. This allows very accurate determination of the Tafel parameters, but makes diffuse double layer correction more difficult, since specific adsorption cannot be excluded. We have tested the effect of specific adsorption of I⁻ by changing the concentration of iodate and by adding as much as 10 mM of NaI. The effect of the chloride was tested by replacing it with fluoride as the anion of the supporting electrolyte. The effect of surface active agents was tested by adding Triton X-100. Small variations in the transfer coefficients were observed between these experiments, but the temperature dependence of α persisted in all cases. Correction for the diffuse double layer effect changes the value of the transfer coefficient, but does not eliminate its temperature dependence.It must be concluded that the transfer coefficient for the reduction of iodate is temperature dependent, and this dependence cannot be attributed to experimental inaccuracy or inadequate correction for the effect of the diffuse double layer resulting from specific adsorption. This is in contrast to our findings for the reduction of bromate, hydroxylamine and the H₃O⁺ ion, for all of which α is found to be strictly independent of temperature.     

Inhibition of the corrosion of iron by oxygen and nitrogen containing compounds

Summary Corrosion inhibition by quinine, ephedrine, brucine, cinchonine, codeine, and harmaline with respect to the dissolution of iron in 2M sulphuric acid was measured using electrochemical methods. Polarization curves indicated that these compounds act as mixed-type inhibitors,i.e. both the cathodic and anodic curves are affected. The observed effect follows theTemkin adsorption isotherm. The effect of the different structural features of these compounds on their inhibition efficiency has been studied. Results indicate that the rate of corrosion of iron increases with increasing temperature over the range 30–50 °C both in the absence and in the presence of inhibitors. Some thermodynamic functions were also computed and are discussed.

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Korrosionshemmung bei Eisen durch Sauerstoff- und Stickstoffverbindungen

Zusammenfassung Die von Chinin, Ephedrin, Brucin, Chinchonin, Codein und Harmalin ausgeübte Korrosionshemmung bei der Auflösung von Eisen in 2M Schwefelsäure wurde mittels elektrochemischer Methoden untersucht. Polarisationskurven zeigen, daß die erwähnten Verbindungen als Inhibitoren gemischten Typs fungieren, d. h. sowohl die kathodische als auch die anodische Kurve wurde beeinflußt. Der beobachtete Effekt folgt derTemkinschen Adsorptionsisotherme. Die Auswirkung von Strukturänderungen auf die Effizienz der Hemmung und einige thermodynamische Funktionen werden diskutiert. Die Korrosionstrate von Eisen steigt sowohl in Gegenwart als auch in Abwesenheit der Inhibitoren im Bereich von 30–50°C mit steigender Temperatur.

     

Mechanism of oxygen releasing of copper ferrite in the formation of the corresponding oxygen-deficient compound

Copper ferrite is a promising material for hydrogen production through thermochemical water splitting. In this work, the cation distribution of copper ferrite and the corresponding oxygen-deficient compound of spinel structure was analyzed based on the crystal structural chemistry theory. The mechanism of oxygen releasing of CuO, Fe₂O₃, CuFe₂O₄ and metal (M=Ni, Mn or Zn) doped copper ferrite in the process of temperature rising was investigated by differential thermal analysis-thermogravimetry (DTA-TG). By combining the theoretical analysis with experimental results, the mechanism of oxygen releasing of copper ferrite is proposed, which is different from that of other ferrites. For copper ferrite, the oxygen releasing caused by Cu(II)→Cu(I) plays a predominant role, while for other ferrites, the oxygen releasing resulting from Fe(III)·Fe(II) is dominant. Supported by the National Defense Fundamental Research Fund (Grant No. A1420080145)     

Green oxidation of alcohols by a reusable nickel catalyst in the presence of molecular oxygen

An easily prepared and reusable Ni(OH)₂ catalyst for the oxidation of benzylic and allylic alcohols by molecular oxygen has been developed.     

Development of an automatic estimation system for both the partition coefficient and aqueous solubility

Summary A computer program has been developed for estimating both the partition coefficient between 1-octanol and water phases and the aqueous solubility from the structural formula. This system is an extended version of a previously described program entitled CHEMICALC for the automatic estimation of the partition coefficient. The aqueous solubility is estimated via two pathways. The first is based on the linear relationship between logarithms of the aqueous solubilities of 497 compounds and their estimated 1-octanol/water partition coefficients. In the second, combined handling of two available group contribution methods of Irmann [Chem. Ing. Tech., 37 (1965) 789] and Wakita et al. [Chem. Pharm. Bull., 34 (1986) 4663] is adopted according to compound type. Some revisions and extensions of the methods for estimating the aqueous solubility have been made in both pathways, and the accuracy of the estimated aqueous solubilities for 497 compounds is discussed.     

Paradigms and paradoxes: energetics of the oxidative cleavage of azo compounds (diazenes)

The enthalpy of oxidative cleavage of azo compounds (diazenes) is discussed and compared with that of symmetric olefins. The roles of substituents and of electronegativity are explicitly discussed.     

Response of halogenated compounds in ion mobility spectrometry depending on their structural features

Ion mobility spectrometry (IMS) with handheld and transportable devices permits the sensitive detection of chlorinated compounds which are important in environmental monitoring. The ion mobility spectra in negative measuring modus mostly show one product ion peak [(H₂O)_nCl⁻] due to dissociative electron attachments. In this paper, we investigated relevant chlorinated compounds (R-Cl) where R represents allyl-, benzyl-, phenyl-, alkyl- and vinyl-groups. These groups cause differences in the R-Cl bond strength and differences in the cleavage of chlorine can therefore be expected. All chlorinated substances investigated provide the same product ion peak at 2.75 cm² Vs⁻¹ independent on the different C-Cl bond strength. However, distinct influences of structural features on the peak intensities of the (H₂O)_nCl⁻ product ion peak were established. Generally, increasing sensitivities were obtained in the order chlorobenzenes < vinyl- < allyl- < alkyl compounds < benzylchlorides. Sensitivities and limits of detection (LODs) of aromatic compounds depend on the nature and position of second substituent. Electron-withdrawing substituents (chlorine, fluorine, nitrile) enhance sensitivity while electron-repelling substituents decrease it. A dependence of sensitivity on the chain length or ring size can be observed for alkyl compounds. Additional influences of intramolecular interactions on the sensitivity were found for di-halogenated compounds. Therefore, the quantification of negative product ion peaks of chlorinated compounds requires a consideration of structural features of analytes.     

Experimental study of the concentration dependence of the soret coefficient by thermal field-flow fractionation: the case of polystyrene in decalin

Summary Thermal field-flow fractionation separates polymers with high selectivity according to their Soret coefficient,S _τ, hence, according to their molar mass, and therefore consitutes an efficeint physicochemical tool for the determination of the Soret coefficient of a given polymer in the carrier liquid from its retention time. However, the polymer concentration in the sample influences the retention time and, hence, the value ofS _τ derived from it. An experimental study of the influence of sample concentration on retention,S _τ, and peak shape was performed for the polystyrene-decalin system over a relatively large temperature domain and for various molar masses. It is found that the retention time and the value ofS _τ increase with increasing sample concentration, the more so as the cold wall temperature is lower. This appears to be in contradiction with the general non-equilibrium thermodynamic expression derived for polymer-solvent systems with positive second virial coefficients, such as the present system over the temperature range investigated. There seems to be a temperature for which the dependence ofS _τ on sample concentration vanishes. This temperature is about 375 K for the polystyrene-decalin system. As the sample concentration increases, the peak barycentre and the standard deviation increases. As the peaks are fronting, the skewness is negative and becomes more negative as the sample concentration increases. The peak skewness appears to be a good indicator of the onset of sample concentration effects. The threshold concentration, for which these effects begin to become significant, decreases with increasing molar mass.     

Electronic absorption spectra of rhenium(VII) compounds: The effect of the coordination number

Changes in electronic absorption spectra in the following series: MeRe(L₂)O₃ McReO3 ReO4– ReO₆5–, have been studied in terms of the qualitative MO scheme.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1563–1566, June, 1996.     

Impact of photosensitized oxidation and singlet oxygen on degradation of stabilized polymers

Photooxidation, an important component of polymer weathering, involves excited polymer-inherent chromophores and photoactive additives and impurities. Quenching of excited species by ground state molecular oxygen, the common component of air, results in the formation of singlet state molecular oxygen ¹O₂. This active form of oxygen is a strong oxygenation agent attacking stabilized polymers. Resulting transformations of the polymer matrix and additives have a negative effect on the service life of the material. The formation of ¹O₂, its properties, and reactions and products arising from stabilizers are outlined.