Optimisation of pressurised liquid extraction for the determination of p,p′-DDT and p,p′-DDE in aged contaminated Ethiopian soils

The effectiveness of extracting p,p′-DDT and p,p′-DDE from aged contaminated soil samples by means of pressurized liquid extraction (PLE) was evaluated. Two soil samples, which were contaminated more than 10 years ago, were used in the investigation. The static extraction time was optimised and then validated against the total sum of target analytes obtained from multiple sequential extractions. The PLE results were also compared with Soxhlet extraction (SOX). PLE for 3×10 min at 100 °C was proven to be more exhaustive than SOX in the determination of p,p′-DDE from both soil samples. In the case of p,p′-DDT, PLE was found to be equally as exhaustive as SOX. Additionally, most of the previous PLE investigations used hazardous organic solvents such as n-hexane, toluene and dichloromethane mixed with acetone, whereas in this investigation the less toxic solvent combination n-heptane/acetone has been employed.     

Synthesis of p,p ′-Phenolphthaleinbis(trimellitic) Dianhydride

p,p′-Phenolphthalein-bis(trimellitic) dianhydride was obtained by the reaction of diacetyloxyphenolphthalein with trimellitic anhydride. The structure of the new compound was proved by elementary analysis, infrared spectroscopy, and acid value determination. The course of acidolysis reaction was examined in the temperature range of 240–280°C. The compound obtained is a powder having a melting point of 135–138° C, has high thermal stability, and is easily soluble in many organic solvents and low-molecular epoxy resins. Application of p,p′-phenolphthalein-bis(trimellitic) dianhydride in synthesis of soluble polyester-imides and as a hardening agent for low molecular weight epoxy resins is proposed.     

Polymesomorphism and orientation in liquid crystalline poly(triethylene glycol p,p′-bibenzoate)

The phase transitions and the orientational behavior of liquid crystalline poly(triethylene glycol p,p′-bibenzoate) have been studied. The real-time synchrotron diffraction results indicate that, on cooling from the isotropic melt, an orthogonal SmA mesophase is formed first, and later it is transformed into a tilted SmC mesophase. However, the SmA mesophase is stable in a rather wide temperature interval, and the transformation into the SmC phase occurs at temperatures close to the glass transition, so that not very high tilting angles are attained. The uniaxial deformation of the SmC mesophase indicates that usual parallel orientation of the molecular axes in relation to the stretching direction is obtained at high strain rates, while anomalous perpendicular orientation occurs at low deformation rates, with the smectic layers aligned with the stretching direction and the molecular axes almost perpendicular. A mixture of the two types of orientation is observed at intermediate rates, with rather interesting features.     

XPS primary excitation spectra of Zn 2p,Fe 2p,and Ce 3d from ZnO, α-Fe2O3, and CeO2

Metal oxides are important for current development in nanotechnology. X-ray photoelectron spectroscopy(XPS) is a widely used technique to study the oxidation states of metals, and a basic understanding of the photoexcitation process is important to obtain the full information from XPS. We have studied core level excitations of Zn 2p, Fe 2p, and Ce 3d photoelectron emissions from ZnO, α-Fe₂O₃, and CeO₂. Using an effective energy-differential XPS inelastic-scattering cross section evaluated within the semiclassical dielectric response model for XPS, we analysed the experimental spectra to determine the corresponding primary excitation spectra, ie, the initial excitation processes. We find that simple emission (Zn 2p) as well as complex multiplet photoemission spectra (Fe 2p and Ce 3d) can be quantitatively analysed with our procedure. Moreover, for α-Fe₂O₃, it is possible to use the software package CTM4XAS (Charge Transfer Multiplet program for X-ray Absorption Spectroscopy) to calculate its primary excitation spectrum within a quantum mechanical model, and it was found to be in good agreement with the spectrum determined by analysis of the experiment.     

pH Dependent plasmon-driven surface-catalysis reactions of p,p′-dimercaptoazobenzene produced from para-aminothiophenol and 4-nitrobenzenethiol

In this paper,we studied the pH dependent plasmon-driven surface-catalysis(PDSC) reactions of p,p’-dimercaptoazobenzene(DMAB) produced from para-aminothiophenol(PATP) and 4-nitrobenzenethiol(4NBT) both theoretically and experimentally.The surface enhanced Raman spectrum(SERS) of DMAB produced from PATP and 4NBT on Ag films in solutions with various pH values has been measured.The simulation and experimental results indicated that the pH dependence of PATP appeared in acidic environment and came from the amino group NH2.Furthermore,the ratio of intensity of Raman peak caused by PATP and DMAB indicated that this acidic sensor had higher pH sensitivity when it was excited by photons of higher energy.     

Use of p,p′-Phenolphthalein-bis(trimellitic) Dianhydride for Hardening Low Molecular Weight Epoxy Resins

Hardening of a low molecular epoxy resin with p,p′-phenol-phthalein-bis(trimellitic) dianhydride has been studied by using differential scanning calorimetry. The relationships of glass transition temperature of the systems being examined versus time, temperature of hardening, and dianhydride content in the compositions have been determined. The activation energy of crosslinking reactions in systems containing 50% of the stoichiometric amount of dianhydride has been evaluated. The value of activation energy obtained indicates a high reactivity of dianhydride in the examined reactions. The hardened epoxy composition exhibits excellent thermal stability, good hardness, and good resistance to acid solutions.

During research on soluble, regularly alternating polyesterimides, a synthesis of p,p′-phenolphthalein-bis(trimellitic) dianhydride was carried out and thus a new compound obtained [1]. The presence in the molecule of this new compound of four functional groups capable of reacting with epoxy groups and good solubility in organic solvents and low molecular epoxy resins suggested the use of this compound as a hardening agent for liquid resins. Examinations of the hardening process were conducted by using a low molecular epoxy resin (Beckopox 37–140) which is equivalent to Epidiane 5 and Epikotc 828.     

Correlation consistent, Douglas–Kroll–Hess relativistic basis sets for the 5p and 6p elements

The diatomic carbon molecule has a complex electronic structure with a large number of low-lying electronic excited states. In this work, the potential energy curves (PECs) of the four lowest lying singlet states ( $X^{1} \Sigma^{ + }_{g}$ , $A^{1} \Pi_{u}$ , $B^{1} \Delta_{g}$ , and $B^{\prime1} \Sigma^{ + }_{g}$ ) were obtained by high-level ab initio calculations. Valence electron correlation was accounted for by the correlation energy extrapolation by intrinsic scaling (CEEIS) method. Additional corrections to the PECs included core–valence correlation and relativistic effects. Spin–orbit corrections were found to be insignificant. The impact of using dynamically weighted reference wave functions in conjunction with CEEIS was examined and found to give indistinguishable results from the even weighted method. The PECs showed multiple curve crossings due to the $B^{1} \Delta_{g}$ state as well as an avoided crossing between the two $^{1} \Sigma^{ + }_{g}$ states. Vibrational energy levels were computed for each of the four electronic states, as well as rotational constants and spectroscopic parameters. Comparison between the theoretical and experimental results showed excellent agreement overall. Equilibrium bond distances are reproduced to within 0.05 %. The dissociation energies of the states agree with experiment to within ~0.5 kcal/mol, achieving “chemical accuracy.” Vibrational energy levels show average deviations of ~20 cm^?1 or less. The $B^{1} \Delta_{g}$ state shows the best agreement with a mean absolute deviation of 2.41 cm^?1. Calculated rotational constants exhibit very good agreement with experiment, as do the spectroscopic constants.     

Spectrophotometric Determination of Cadmium(II) Using p,p′‐Dinitro‐SYM‐Diphenylcarbazid in Aqueous Solutions

Abstract

A sensitive and selective spectrophotometric method is proposed for the rapid determination of cadmium(II) using, p,p′‐dinitro‐sym‐diphenylcarbazid, directly in aqueous solution. The reaction between cadmium(II) and p,p′‐dinitro‐sym‐diphenylcarbazid occurs immediately in strong basic media (0.02 N sodium hydroxide solution). The complex shows a maximum of absorption at 630–640 nm, and the absorbance remains stable for at least 24 h. The method allows the cadmium determination over the range 0.5–6.0 µg mL^?1, with a molar absortivity of 2.05×10⁴ L mol^?1 cm^?1 and features a detection limit of 0.13 ppm. The interferences caused by several ions [Ca(II), K(I), Ba(II), Al(III), Pb(II), Zn(II), Cl^?1, NO₃ ^?, SO₄ ^2?], which are present in most of environmental samples, were determined. The validation of the spectrophotometric method was done by recovery test of cadmium(II) in tap water and sea water. The results show that the proposed method has been successfully applied to the determination of cadmium(II) in water samples.     

p,p′-芳炔桥连的四联萘拓扑环芳分子的设计与合成

基于联萘衍生物手性构型高度稳定的特点, 以光学活性的(R)-2,2'-二乙炔基-1,1'-联萘为模板, 设计了3个有趣的拓扑环芳分子——含有4个手性联萘单元的(R,R,R,R)-2a～2c, 并探讨了它们的合成. 合成路线涉及三甲基硅(Me₃Si-)保护基的控制导入, 对位取代的芳基连接桥的链接, 保护基的脱去以及分子间偶合成环4个步骤. 用比旋光度([α]_D), MS, IR, UV-Vis, ¹H和¹³C NMR以及元素分析表征了这些化合物.     

Design,Synthesis, and Biological Evaluation of Tetra-Substituted Thiophenes as Inhibitors of p38α MAPK

p38α mitogen-activated protein kinase (MAPK) plays a role in several cellular processes and consequently has been a therapeutic target in inflammatory diseases, cancer, and cardiovascular disease. A number of known p38α MAPK inhibitors contain vicinal 4-fluorophenyl/4-pyridyl rings connected to either a 5- or 6-membered heterocycle. In this study, a small library of substituted thiophene-based compounds bearing the vicinal 4-fluorophenyl/4-pyridyl rings was designed using computational docking as a visualisation tool. Compounds were synthesised and evaluated in a fluorescence polarisation binding assay. The synthesised analogues had a higher binding affinity to the active phosphorylated form of p38α MAPK than the inactive nonphosphorylated form of the protein. 4-(2-(4-fluorophenyl)thiophen-3-yl)pyridine had a K_i value of 0.6 μm to active p38α MAPK highlighting that substitution of the core ring to a thiophene retains affinity to the enzyme and can be utilised in p38α MAPK inhibitors. This compound was further elaborated using a substituted phenyl ring in order to probe the second hydrophobic pocket. Many of these analogues exhibited low micromolar affinity to active p38α MAPK. The suppression of neonatal rat fibroblast collagen synthesis was also observed suggesting that further development of these compounds may lead to potential therapeutics having cardioprotective properties.     

Die Umwandlungswärme von p,p′-Azoxyanisol beim Übergang kristallin/flüssig zu flüssig

Ohne Zusammenfassung     

Synthesis of Cyanobenzaldehydes （m—,o—,p—）by Molecular oxygen Oxidation Methods

Cyanobenzaldehydes (m-,o-,p-) were synthesized by oxidation of corresponding tolunitriles with molecular oxygen,catalyzed by cobalt acetate and sodium bromide.     

Evaluation of Transient Absorption Spectra of N,N,N’,N’—Tetra—（p—methylphenyl）

Photoinduced electron transfer processes between fullerenes(C60/C70)and N,N,N’,N’-tetra-(p-methylphenyl-4,4’-diamino-1,1’-diphenyl ether(TPDAE)have been studied by nanosecond laser flash photolysis.Quantum yields and rate constants of electron trasfer from TPDAE to excited triplet state of fullerenes(C60/C70)in benzonitrile have been evaluated by observing the trasient absorption bands in the near-IR region where the excited triplet state.radical anion of fullerenes(C60/C70)and radical cations of TPDAE appear.     

Low-Valent Group 14 Phosphinidenide Complexes [({SIDipp}P)2M] Exhibit P–M pπ–pπ Interaction (M=Ge,Sn, Pb)

Herein, the synthesis of new low-valent Group 14 phosphinidenide complexes [({SIDipp}P)₂M ] exhibiting P–M pπ–pπ interactions (SIDipp=1,3-bis(2,6-diisopropylphenyl)-imidazolidin-2-ylidene, M=Ge, Sn, Pb), is presented. These compounds were investigated by means of structural, spectroscopic, and quantum-chemical methods. Furthermore, the monosubstituted compounds [(SIDippP)MX]₂ (M=Sn, X=Cl; M=Pb, X=Br) are presented, which show dimeric structures instead of multiple bonding interaction.     

Synthesis,Electrical, Electronic and Charge Transport Properties of Poly(aniline‐co‐p‐toluidine)

Copolymers of aniline with p‐toluidine were synthesized for different molar ratios of the respective monomers in acid medium. The electrical conductivity, charge transport and spectral characteristics upon incorporation of p‐toluidine units into the polyaniline backbone were investigated. The electrical conductivity of the copolymers showed frequency dependence which became more prominent with an increase in the number of p‐toluidine units in the polyaniline backbone. A direct relationship between the frequency dependence and electron localization was observed in the copolymers. Electronic spectra showed blue shifts in the π→π*and benzenoid→quinoid transitions revealing a decrease in the extent of conjugation in the copolymers. The protonated forms of the copolymers were soluble in DMSO giving polaron band around 400 nm. The decrease in electrical conductivity was attributed to the greater electron localizations as revealed from the broader ESR signals. Temperature dependence of electrical conductivity showed that charge transport was mainly through variable range hopping though a mixed conduction behavior was observed at higher temperature range.