共查询到20条相似文献,搜索用时 15 毫秒
1.
Science China Chemistry - We call a subgroup H of a finite group G c-supplemented in G if there exists a subgroup K of G such that G = HK and H ∩ K ≤ core(H). In this paper it is proved... 相似文献
2.
Nitrated and chlorinated derivatives ofp-xylene-formaldehyde resin were prepared and the resin samples were characterised by IR and NMR spectra. The average molecular
weight of the resin samples was determined by vapour pressure osmometry. Kinetic parameters were determined from differential
thermal analysis and thermogravimetry using Chatterjee, Anderson-Freeman, Broido, Flynn and Wall, Reich and Kissinger methods. 相似文献
3.
A cndo/2 study has been carried out for C6F6 + C6H6aad C6F6 + C6H10 composites and individual molecules. The favoured configurations of the adducts have been decided on the basis of energy
calculations of various geometries. For the C6F6+C6H6 adduct the lowest energy corresponds to the configuration in which the molecular planes are parallel to each other with a
twist angle of 30°. For the C6F6+ C8H10 adduct lowest energy corresponds to a geometry in which the two molecular planes are inclined by a small angle with the angle
of twist between the molecular planes being 30°. It is shown that the complexes are not of the charge transfer type. 相似文献
4.
Hong-bo Li Meng-an Hao Chuan Qin Wen-bing Yang Xiao-ping Hu Sheng-ying Qin 《Reaction Kinetics and Catalysis Letters》2007,91(2):299-306
Cobalt (II) hydroxamates with the benzo-15-crown-5 (B15C5) pendant have been synthesized and characterized. These complexes
were successfully employed to the oxidation of p-xylene to p-toluic acid with air at 110°C under normal atmospheric pressure. The effects of the B15C5 pendant, the length of chain bonding
of B15C5 in these complexes and the addition of alkali metal ions on the oxidation for p-xylene are also investigated by the comparison with the crown-free analogue. 相似文献
5.
Zorana Grabari Boidar S. Grabari Miquel Esteban Enric Casassas 《Journal of Electroanalytical Chemistry》1997,420(1-2)
Ratio differential pulse polarograms obtained by dividing the multianalyte and single analyte signals are proposed as a tool for resolution of global signals and quantification of the analytes from a qualitatively known mixture by differential pulse polarography (DPP) and related electroanalytical techniques. The influences of shape and position of the resolving function (DP polarograms of individual analyte) on the efficiency of resolution are discussed on simulated and experimental results. The method is applied for the determination of p-nitroaniline (NA) and p-nitrotoluene (NT) from their mixture in N,N′-dimethylformamide solutions with 0.1 M tetrabutylammonium iodide as supporting electrolyte, using an external calibration diagram and internal standard addition methods. NA and NT give one-electron DP polarographic peaks with 93 mV of peak separation and, therefore, show significant overlapping which depends on the concentration ratio of NA and NT in the mixture. The method is especially suitable for quantification of one analyte in the presence of a large excess of another analyte, because by division the component in excess is removed and the pseudo-ratio DPP of the minor component is clearly revealed in a way which is not possible by deconvolution using polynomial division or deconvolution by Fourier transforms. 相似文献
6.
R. Usha Nanasaheb P. Thakare Shriniwas L. Kelkar Murzban S. Wadia 《Journal of Chemical Sciences》1991,103(2):195-200
Two distinct reaction mechanisms are proposed for the reactions of1,5 and6 with nucleophiles as against those of11,12 and16. The former set undergoes the reactions through carbocation type intermediates2 and3 as efficiently as the stable carbocation4 does, even under similar and very mild conditions. The compounds from the latter group do not form the carbocations under
the same conditions and undergo only direct substitution by strong nucleophiles. 相似文献
7.
Raman phonon spectroscopy has been used to study photodimerization reaction inp-chloro cinnamic acid (pCCA) crystal. The β-form of the crystal yields the 4,4′-dichloro-β-truxinic acid dimer. Six distinct low frequency phonon
bands are observed in thepCCA monomer crystal. On reaction progress, these bands show a monotonic shift to lower frequencies and broaden out. Finally,
in the dimer crystal the phonon spectrum shows two weak broad bands. These results suggest that the reaction is homogeneous
in the initial stages and, as the product concentration increases, the lattice becomes highly disordered. The reactant and
the product were characterised by infrared and Raman spectroscopy. The disappearance of aliphatic C=C bond stretching vibration
and appearance of cyclobutane ring deformation and cyclobutane ring-breathing vibrations on reaction confirm photodimerization
by cyclobutane ring formation. The large Stoke's shift between the absorption and emission band suggest strong exciton-phonon
coupling in the monomer lattice. This reaction seems to be phonon-mediated. 相似文献
8.
Ring-opening suspension polymerization of p-dioxanone(PDO) in supercritical carbon dioxide(scCO2) was investigated in the presence of poly(caprolactone)-perfluropolyether-poly(caprolactone)(PCL-PFPE-PCL).The molecular weight,yield and particle morphology of poly(p-dioxanone)(PPDO) were studied.The stabilizer was effective to stabilize the ring-opening polymerization(ROP) of PDO in scCO2,leading to the formation of resorbable microparticles in a"one pot"procedure.The mean size of PPDO microparticles obtained from suspension polymerizations was sensitive to the rate of agitation and the stabilizer concentration.The method to generate PPDO microparticles has overcome its unprocessable drawback with common organic solvents and provided new product form for biomedical applications. 相似文献
9.
Jongho Kim Sang Wook Kang Yong Soo Kang 《Colloids and surfaces. A, Physicochemical and engineering aspects》2008,320(1-3):189-192
Partially positively charged silver nanoparticles were successfully prepared by interaction between p-benzoquinone and the surface of the nanoparticles. This result was primarily due to electron affinity of the carbonyl group in p-benzoquinone, as confirmed by FT-IR and X-ray photoelectron spectroscopy (XPS). In this study, p-benzoquinone acted as both a stabilizer and a reducing agent for silver nanoparticles. UV–vis spectra showed the formation of silver nanoparticles. TEM micrographs confirmed that most of silver nanoparticles exist in sizes less than 7 nm, and the average size of particle aggregates is approximately 20 nm. 相似文献
10.
Yury A. Skorik Galina V. Romanenko Carlos A. R. Gomes Ludmila K. Neudachina Alexander A. Vshivkov 《Polyhedron》2002,21(27-28)
The copper(II) complex [Cu(p-Tdp)(H2O)2]·2H2O, where p-Tdp is the anion of p-toluidine-N,N-di-3-propionic acid (or N,N-di(2-carboxyethyl)-p-toluidine), has been synthesized and characterized by X-ray diffraction. Three crystallographically independent [Cu(p-Tdp)(H2O)2] molecules have a similar structure. The Cu atoms have a square pyramidal environment (4+1) with a small trigonal bipyramidal distortion. The ortho-H atom of the benzene ring blocks up the sixth coordination position of the Cu polyhedron. The basal plane is formed by the donor atoms of the tridentate ligand and by the water molecule (average bond length Cu---N 2.03, Cu---O 1.93, Cu---Ow 2.00 Å), the apex is occupied by another water molecule (Cu---Ow 2.27 Å). The Cu atoms are located 0.20–0.30 Å out of the mean planes of the four basal atoms towards the apical Ow atom. The IR and electronic absorption spectra of p-Tdp and the title compound have been described. UV–Vis reflectance spectra shows that the complex has the same square pyramidal geometry in the crystal state and in solution. The protonation constants of the ligand log K1=6.87(2), log K2=3.75(2), log K3=2.57(2) and stability constants log KCuH(p-Tdp)=2.13(5), log KCu(p-Tdp)=6.38(3) were determined by pH-titration at 25.0 °C and I=0.1 M KNO3. 相似文献
11.
M. Judith Percino Víctor M. Chapela Omar Urzúa Ling-Fa Montiel Cecilia Rodríguez-Barbarín 《Research on Chemical Intermediates》2007,33(7):623-629
The novel intermediate 1-(p-fluorophenyl)-2-(2′-pyridyl)ethanol or 2-[2′-(1-hydroxy-1-(p-fluorophenyl)ethyl]pyridine and the corresponding novel dehydration compound 1-(p-fluorophenyl)-2-(2′-pyridyl)ethene or 2-[p-fluorophenylvinyl]pyridine were obtained from the condensation reaction of p-fluorophenylaldehyde and 2-picoline under catalyst-and solvent-free conditions. The intermediate 1-(p-fluorophenyl)-2-(2′-pyridyl)ethanol was obtained at 42 h reaction time and temperature of 120°C, respectively. 1H-NMR, IR spectroscopic data of the 1-(p-fluorophenyl)-2-(2-pyridyl)ethanol clearly showed the presence of the-CH2-CHOH-group. The compound was obtained as a white powder with m.p. 121–122°C and a yield of 8%. For 1-(p-fluorophenyl)-2-(2-pyridyl)ethene, the reaction conditions were similar, but the reaction temperature was increased to yield
the double bond in the 1-(p-fluorophenyl)-2-(2′-pyridyl)ethene. At the reaction temperature of 140°C, the compound was a slightly brown powder with a
m.p. of 78°C and yield of 18%. 1H-NMR, IR spectroscopic data for the 1-(p-fluorophenyl)-2-(2′-pyridyl)ethene showed the presence of a double bond in trans configuration (-CH=CH-), characteristic of a styrylpyridine. 相似文献
12.
Trino Suárez Bernardo Fontal Ghery Zambrano Marisela Reyes Fernando Bellandi Ricardo R. Contreras Juan C. Diaz Pedro Cancines Yuraima Fonseca Isolda Romero 《Reaction Kinetics and Catalysis Letters》2008,94(1):21-26
Reaction between Mo(CO)6 and p-C5NH4SO3Na (1:2 (Mo: p-C5NH4SO3Na) stoichiometric ratio) gave the trans-Mo(CO)4(p-C5NH4SO3Na)2 complex, (1), in 80% yield. Complex (1) has been characterized by FTIR, 1H and 13C NMR spectroscopy. Complex (1) has most likely an idealized D4h geometry with trans N-bound p-C5NH4SO3Na ligands. 相似文献
13.
Song-Dong Ding Guang-Can Zheng Jian-Bing Zeng Li Zhang Yi-Dong Li Yu-Zhong Wang 《European Polymer Journal》2009,45(11):3043-3057
A series of poly[p-dioxanone-(butylene succinate)] (PPDOBS) copolymers were prepared from p-dioxanone (PDO), 1,4-butanediol and succinate acids through a two-step process including the initial prepolymer preparation of poly(p-dioxanone)diol (PPDO-OH) and poly(butylene succinate)diol (PBS-OH) and the following copolymerization of the two kinds of prepolymers by coupling with hexamethylene diisocyanate (HDI). The molecular structures of the prepared PPDO-OH, PBS-OH and PPDOBS were characterized by hydrogen nuclear magnetic resonance spectroscopy (1H NMR). The crystallization of the copolymers was investigated by using differential scanning calorimetry (DSC), polarized optical microscopy (POM) and wide angle X-ray diffraction (WAXD). It has been shown that the crystallization rate and the degree of crystallization increases with the increase of the weight fraction of poly(butylene succinate) (PBS) blocks in the copolymers. In phosphate buffer solution with pH 7.4 at 37 °C for 18 weeks, the hydrolytic degradation behaviors of the copolymers were studied. The changes of retention weight, water absorption, pH value, and surface morphologies with the degradation time showed that the hydrolytic degradation rate of PPDOBS could be controlled by adjusting the weight fraction of poly(p-dioxanone) (PPDO) and PBS blocks in the copolymers. The changes of the thermal properties of PPDOBS during the degradation were also investigated by DSC. 相似文献
14.
Complexation reactions of bivalent metal ions and ethyl-2,3-dioxobutyrate-2p-bromophenylhydrazone (EDOB-2p-BPH) have been studied potentiometrically in 50% (v/v) ethanol/water medium at different ionic strengths with respect to
NaClO4 and at different temperatures and their stability constants determined. The method of Bjerrum and Calvin as modified by Irving
and Rossotti has been used to determine then andpL values. Smin values which have the same significance as ‘T2’ have also been calculated. The thermodynamic stability constants and standard free energy change (ΔG) have also been calculated.
ΔG values are negative in all cases indicating that the reactions are spontaneous. The ligand field stabilization energy (δH)
has also been calculated for the 3d transition metals. 相似文献
15.
6-取代苯并噻唑苯胺类化合物的合成 总被引:1,自引:0,他引:1
以2-氨基苯并噻唑类化合物为原料, 通过碱性条件下水解, 与苯甲酸类化合物在PPA(聚磷酸)条件下脱水环化, 部分化合物通过BBr3去甲基化反应, 合成了一系列潜在的针对β-淀粉样蛋白的正电子放射性探针分子前体或作为参比的6-取代苯并噻唑苯胺类化合物, 并用1H NMR, IR, EI/ESI-MS, HRMS, 元素分析等对其进行了表征. 同时测定比较了6种化合物与早老性痴呆(Alzheimer’s disease, AD)死者脑匀浆的亲和力强弱. 相似文献
16.
Guocheng Xu Wei Wang Xiaofei Qu Yansheng Yin Lei Chu Benlin He Huikang Wu Jingrui Fang Yusheng Bao Liang Liang 《European Polymer Journal》2009,45(9):2701-2707
Polyaniline was deposited potentiodynamically on a stainless steel substrate in the presence of an inorganic acids (sulfuric acid). The electrochemical characterization of the electrode was carried out by means of cyclic voltammetry and electrochemical impedance spectroscopy in the organic acids (p-toluene sulfonic acid) solution. The results show that polyaniline has a high specific capacitance of 431.8 F g−1 at 1 mV s−1, high coulombic efficiency of 95.6% at 20 mV s−1, and exhibits a high reversibility. This indicates the promising feasibility of the polyaniline used as an electrochemical capacitor material in the electrolyte of p-toluene sulfonic acid solution especially at high charge–discharge process. 相似文献
17.
The reactions were sensitive between seven rare earth (RE) metals Nd(III), La(III), Ce(III), Pr(III), Sm(III), Eu(III) and
Gd(III) and dibromo-p-methylmethylsulfonazo (DBMMSA) in acidic solution. The spectral correction method has been applied in
the determination of properties of RE complexes instead of ordinary spectrophotometry. Composition ratios, real molar absorptivities
(ε) and stepwise stability constants (K) of each of the RE complexes were determined easily because the method eliminated
the absorption influence of excess of ligand on complex. Results showed that the cumulativeK values of the complexes were between 3.91 × 1014 and 2.34 × 1028 and the real (not apparent) absorptivity between 8.85 × 104 and 2.12 × 105 l mol-1cm-1 at 640 nm. 相似文献
18.
A novel capacitive sensor for pazufloxacin mesilate (pazufloxacin) determination was developed by electropolymerizing p-aminobenzene sulfonic (p-ABSA) and molecularly imprinted polymers (MPs), which was synthesized through thermal radical copolymerization of metharylic
acid (MAA) and ethylene glycol dimethacrylate (EGDMA) in the presence of pazufloxacin template molecules, on the gold electrode
surface. Furthermore, 1-dedecanethiol was used to insulate the modified electrode. Alternating current (ac) impedance experiments
were carried out with a Model IM6e to obtain the capacitance responses. Under the optimum conditions, the sensor showed linear
capacitance response to pazufloxacin in the range of 5 ng·mL−1 to 5 μg·mL−1 with a relative standard deviation (RSD) 5.3% (n=7) and a detection limit of 1.8 ng·mL−1. The recoveries for different concentration levels of pazufloxacin samples varied from 94.0% to 102.0%. Electrochemical experiments
indicated the capacitive sensor exhibited good sensitivity and selectivity and showed excellent parameters of regeneration
and stability.
Supported by the National Natural Science Foundation of China (Grant No. 20675064), the Natural Science Foundation of Chongqing
City (Grant No. CSTC-2004BB4149 and 2005BB4100) and High Technology Project Foundation of Southwest University (Grant No.
XSGX02). 相似文献
19.
对氨基苯磺酸两步法修饰多壁碳纳米管 总被引:1,自引:0,他引:1
用混酸处理多壁碳纳米管, 利用侧壁生成的羧酸基团, 在N,N-二环己基碳酰亚胺的作用下, 使对氨基苯磺酸接枝到碳纳米管表面. 以浓硫酸为磺化剂, 室温下制备了磺化聚醚醚酮(SPEEK). 然后采用溶液共混法制备了磺化聚醚醚酮/接枝多壁碳纳米管复合膜. 采用傅立叶变换红外光谱(FT-IR)、热重分析(TGA)、透射电镜(TEM)、拉曼光谱(Raman)等技术对碳纳米管的结构和性能进行了表征. 红外谱图表明对氨基苯磺酸上的氨基与碳纳米管表面的羧基发生了反应, 生成酰胺基团. 热重曲线表明碳管表面接枝的有机基团的比重达到40%. 拉曼光谱显示处理前后碳管的ID/IG值变化不大, 表明碳管的石墨结构的含量基本不变. 复合膜的力学性能测试结果表明, 对氨基苯磺酸接枝的碳管可以提高膜的拉伸强度. 相似文献
20.
Renhua Shen Chinami Akiyama Takamichi Senyo Koichi Ito 《Comptes Rendus Chimie》2003,6(11-12):1329-1335
Poly(ethylene oxide) (PEO) macromonomers with α-p-vinylphenylalkyl (propyl, pentyl, and hexyl) and ω-hydroxy end groups were applied to emulsion and dispersion polymerization of styrene as reactive emulsifiers and dispersants in water and in methanol-water mixture (9:1 v/v), respectively. Nearly monodisperse microspheres of submicron to micron size were obtained. Particle size in the emulsion system was one or half order of magnitude smaller than that in the dispersion system, while in both systems the size decreased approximately according to minus one half power of the macromonomer concentration in weight. The particle size was substantially independent on the PEO chain length and also on the spacer alkyl chain length of the α-polymerizing end group. The total weight of the PEO chains incorporated by copolymerization into the particle surfaces (shells), relative to that of styrene polymerized into the particle cores, appears to be a key factor for controlling the particle size. To cite this article: K. Landfester et al., C. R. Chimie 6 (2003). 相似文献