Evidence of poly-condensed aromatic rings in a Victorian brown coal

An attempt was made for obtaining UV/VIS absorption and fluorescence spectra of a whole Victorian brown coal and then examining the presence of aromatic ring systems (ARSs) with poly-condensed rings in the coal. Loy Yang brown coal was subjected to an alkali-promoted depolymerization in an aqueous solution of sodium hydroxide at 473 K and then dissolved nearly completely into the solution. The solution of the solubilized coal was analyzed by UV/VIS absorption and fluorescence spectroscopies. The spectra of the solubilized coal were compared with those of a tar that was produced from the rapid pyrolysis of the coal in a wire-mesh reactor. Absorbance of the solubilized coal per unit molar concentration of aromatic carbon and unit light path length was averaged over 50 nm wavelength intervals in a range from 250 to 600 nm. The averaged absorbance of the solubilized coal was much greater than those of mono-aromatic compounds and lignin at intervals from 400 to 600 nm while comparable to those of tetra- to hexa-aromatic compounds, suggesting that the coal is abundant of ARSs with poly-condensed rings. The fluorescence spectra of the solubilized coal also give indication of the presence of ARSs with three to six condensed rings. Furthermore, the presence of even larger ARSs is evidenced from appreciable difference in apparent quantum yield of the solubilized coal and that of the tar. By comparing the absorption and fluorescence spectra of the solubilized coal with those of the tar, it was revealed that the tar is richer in relatively small poly-ARSs than the solubilized coal while the larger poly-ARSs are abundant in the solubilized coal. Smaller poly-ARSs were thus released from the coal preferentially to larger poly-ARSs during the pyrolysis.     

Hyperbranched aromatic polyesters: From synthesis to applications

During the last two decades, hyperbranched polymers have become the focus of interdisciplinary research, and received considerable attention due to their unique chemical and physical properties as well as their potential applications. As an important class of hyperbranched polymers, aromatic hyperbranched polyesters have attracted increased interest and are intensively studied because of their excellent thermal stability, chemical resistance, and mechanical properties. This article reviews the developments in synthesis, modifications, and applications of aromatic hyperbranched polyesters.     

α-溴化芳香酮合成方法的改进

在氧化铜存在的条件下,以单质溴为溴源,芳香酮可有效地转化成相应的α-溴代酮,所有产物结构都通过了核磁共振氢谱的表征。     

Novel facile photochemical method for the synthesis of trivalent nickel azamacrocyclic complexes

Photolysis in the charge-transfer-to-solvent bands of the nickel(II) azamacrocyclic complexes in aqueous solutions yields trivalent nickel azamacrocyclic complexes.     

Tetrapyrazinoporphyrazines with different number of peripheral pyridyl rings: Synthesis,photophysical and photochemical properties

Zinc tetrapyrazinoporphyrazines comprising different numbers of pyridin-2-yl and tert-butylsulfanyl substituents were prepared by the statistical condensation of two precursors – 5,6-bis(tert-butylsulfanyl)pyrazine-2,3-dicarbonitrile (A) and 5,6-dipyridin-2-yl-pyrazine-2,3-dicarbonitrile (B). The ensuing zinc tetrapyrazinoporphyrazines were chromatographically separated on silica column and characterized. Adjacent (AABB) and opposite (ABAB) isomers were not separated. The prepared zinc tetrapyrazinoporphyrazines did not differ in their Q-band position but the B-band position was shifted hypsochromically for compounds bearing more pyridyl units; in addition, a weak band at 450–520 nm decreased with increasing number of pyridyl substituents. Singlet oxygen quantum yields (Φ_Δ in the range 0.69–0.53) decreased with increasing number of pyridyl units on the macrocyclic core, while fluorescence quantum yields showed the reverse tendency (Φ_F in the range 0.22–0.26).     

Estimation of sublimation enthalpies of solids constituted by aromatic and/or polycyclic aliphatic rings by using a group contribution method

A group contribution (GC) method is developed to predict the sublimation enthalpy of only any compound constituted with polycyclic aromatic hydrocarbons and/or polycyclic aliphatic rings with an average absolute relative deviation of 8.98% and an average absolute error of 9.22 kJ·mol^?1. A statistical analysis (ANOVA table) and two validation tests are performed to show the consistency of the method. This GC method can speed up several processes in which it is required the value of the sublimation enthalpy of a solid with these characteristics (pharmaceuticals for instance). However, this method must not be used with inorganic compounds or organic solids with noncyclic structure. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

Modified method for determining aromatic diamines during the synthesis of oligomeric para-aramids

A modified high-performance liquid chromatography method for determining the quantitative content of unreacted paraphenylenediamine and diaminophenylbenzimidazole in the presence of dimethylacetamide is proposed. The method includes acetylation of the reaction mixture after copolycondensation of the para-oligomeric copolyamide in the presence of an excess of the aromatic diamines.     

Thermal degradation in oxygen of polymers with aromatic rings in the chain

The thermal degradation in oxygen of fifteen polymers containing aromatic rings in the chain has been studied by a weight loss method. The relative thermal stabilities of the different polymers have been determined and, where possible, the overall activation energy for breakdown. The results have been compared with those for samples of the same polymers degraded in vacuum. The most thermally stable of the polymers examined under oxidizing conditions was poly(2,6-dichlorophenylene oxide), with a stability comparable with that of a copolymer of tetrafluoroethylene and hexafluoropropylene.     

芳乙酮类化合物在农药合成中的应用

芳乙酮类化合物以其结构衍生化手段的多样性以及生物活性上的重要性而在有机合成中有着广泛的应用.综述了芳乙酮类化合物在农药开发中的应用.     

Heteroatom-directed aromatic lithiation: a versatile route to the synthesis of organochalcogen (Se, Te) compounds

Chiral and achiral organochalcogen compounds bearing a heteroatom in close proximity are easily accessible via the directed aromatic lithiation route. The lithium chalcogenolates prepared by the insertion of selenium or tellurium into the C-Li bond are used to synthesize various chalcogen compounds such as Se/Te, N donor ligands, dichalcogenides, monomeric metal chalcogenolates, and macrocycles. The differences in the stability and reactivity of the organochalcogen compounds derived from various substrates are described in terms of electronic and stereochemical properties of donor atoms.     

Polymerization of maleimides containing s-triazine rings in presence of aromatic di- or tri-amines

Summary New thermosetting resins were prepared by crosslinking of 2,4,6-tris[4-(maleimido) phenoxy]-s-triazine (TM) or 2,4-bis[4-(maleimido) phenoxy]-6-diethoxyphosphinyl-s-triazine (BM) in presence of various aromatic di- or tri-amines. The maleimide-amine adducts initiated thermal polymerization at lower temperature than did the corresponding neat maleimides. The thermal stability of cured resins was evaluated by thermogravimetric analysis. The cured resins derived from the maleimide-amine adducts were less thermally stable than those of the corresponding neat maleimides. The initial decomposition temperature of the polymers obtained from the maleimide-amine adducts was not remarkably influenced by the chemical structure of the aromatic amine utilized.     

Amine-terminated aromatic and semi-aromatic hyperbranched polyamides: synthesis and characterization

A facile synthetic approach to aromatic and semiaromatic amine-terminated hyperbranched polyamides via direct polymerization of triamine (B₃) with different diacid chlorides (A₂) was explored. An aromatic triamine, 1,3,5-tris(4′-aminophenylcarbamoyl)benzene (TAPCB), was synthesized and monomers were characterized by elemental analysis, FTIR, ¹H and ¹³C NMR spectroscopy. Finally, the polycondensation reaction of TAPCB with terephthaloyl chloride (TPC), isophthaloyl chloride (IPC), sebacoyl chloride (SC) and adipoyl chloride (AC) resulted in the preparation of four hyperbranched polyamides i.e., HBPA 1, 2, 3 and 4, respectively. FTIR and ¹H NMR analyses confirmed the structures of the ensuing polymers and DB was found between 0.51–0.55. These thermally stable amorphous HBPAs were soluble in polar aprotic solvents at room temperature having glass transition temperatures (T_g) between 138–198 °C. Inherent viscosities (η_inh) and weight average molecular weights (M_w) were in the range of 0.27–0.35 dL/g and 1.3 × 10⁴–2.7 × 10⁴, respectively. Future prospects are envisaged.     

Direct conversion of synthesis gas to aromatic hydrocarbons: Variation of product distribution with time-on-stream

The synthesis of hydrocarbons from syngas was studied over a zirconia-based cobalt-nickel catalyst (FT catalyst) alone as well as mixed with zeolite HZSM-5 at 101.3 kPa in a 12.7 mm i.d. down flow reactor. The product distribution was recorded as a function of time-on-stream for several days of continuous operation under fixed operating conditions of 250°C and H₂/CO = 1. For the FT + HZSM-5 system, a dramatic variation in the product distribution takes place during the first 24 h of operation. A comparison of time-on-stream results obtained using FT catalyst alone and mixed with HZSM-5 suggests that the reactions leading to the build-up of overall product distribution are slower over HZSM-5 compared to those taking place over FT catalyst. These differences have been attributed to the different nature of reactions taking place over the two components of the mixed catalyst system. Analyses of the coke on the deactivated catalysts are also reported.     

The synthesis and properties of a series of aromatic dendritic polyamides

Summary A series of three aromatic polyamide dendrimers are reported. The materials were prepared via a convergent growth approach and are monodisperse by GPC. We have analysed the dendrimers by a variety of standard techniques and report some conformational effects that can be observed in their¹H NMR spectra.     

新型芳香族聚酯多元醇的合成与性能研究

用对苯二甲酸、苯酐、二元醇、三元醇等多元醇为原料制备新型芳香族聚酯多元醇,考察了聚酯多元醇酸值、羟值与其醇酸摩尔比的关系,以及酸值与反应时间的关系,并将其用于制备硬质聚氨酯泡沫塑料,讨论了新型聚酯多元醇对硬质聚氨酯泡沫塑料的性能影响。     

Photoresponsive polymers having pendant chlorocinnamoyl moieties: synthesis, reactivity ratios and photochemical properties

New photoreactive homo- and copolymers containing pendant chlorocinnamoyl moieties were respectively synthesized by homopolymerization of corresponding acrylic monomer and copolymerization with glycidyl methacrylate. The diverse structures were characterized by different spectroscopic techniques. The thermal properties of the photosensitive polymers were investigated by thermogravimetric analysis in air and differential scanning calorimetry under nitrogen atmosphere. The compositions of polymers were determined by ¹H-NMR analysis. The reactivity ratios of both comonomers were calculated using the conventional linearization methods such as Fineman-Ross, Kelen-Tudos, extended Kelen-Tudos and a non-linear error-in-variables model (EVM) method using a computer program, RREVM, in order to optimize the reaction conditions for industrial applications. The photoreactivity of newly synthesized homo- and copolymers containing pendant chlorocinnamoyl moieties was investigated in solution as well as in thin films. The effects of solvent nature, concentration, temperature, copolymer compositions and photosensitizers on the rate of photocrosslinking of these new photoresponsive polymers were evaluated. Suitable conditions were discussed for using as negative photoresists in industries.     

Novel chalcone-based aromatic polyamides: synthesis,characterization, and properties

Two novel diacid-based monomers have been synthesized by anchoring a benzylideneacetophenone (chalcone) moiety through an amide or ester bridge at the fifth position of the isophthalic acid ring. Two series of new polyamides bearing chalcone side chains were prepared by direct polycondensation reaction of the aforementioned dicarboxylic acids and various aromatic diamines in N-methyl-2-pyrrolidinone, using triphenyl phosphite and pyridine as condensing agents. Their molecular structure and the basic properties were investigated by nuclear magnetic resonance, Fourier-transform IR and UV–vis spectroscopy, differential scanning calorimetry, thermogravimetric analysis, and wide-angle X-ray diffraction. The inherent viscosity, molecular weights measurements (by gel permeation chromatography), water uptake, and solubility tests completed the research study. Introduction of the rigid and bulky chalcone units into the polymer side chains improved remarkably the solubility of the aromatic polyamides, endowed them with an amorphous nature, good thermal stability, and photosensitivity. The resulting polymers were obtained in good yields, inherent viscosities varied between 0.49 and 0.86 dL/g, and their relative high molecular weights conferred them film-forming properties. They were soluble in amide-type polar solvents, such as N,N-dimethylformamide, dimethyl sulfoxide, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone. These polyamides had glass transition temperatures between 219 and 264 °C, and 10% weight loss temperatures in the range of 394–436 °C and around 50% residue at 700 °C in nitrogen atmosphere. The polyamides underwent a [2 + 2] photocycloaddition reaction upon UV light irradiation both in solution and film state in the absence of a photoinitiator or photosensitizer. The polymer films became insoluble in solvents as a result of the crosslinking .     

芳香醛和芳香胺参予的Mannich反应及其合成应用

研究了芳香胺和芳香醛参予的Ｍａｎｎｉｃｈ反应及其合成应用，以它们的原料合成了１０余种新的Ｍａｎｎｉｃｈ碱，也使Ｍａｎｎｉｃｈ反应由单一甲醛扩展到芳香醛，产率为６２．３％～９０．４％。