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1.
In the presence of triethylamine, 2-mercaptobenzoic acid readily adds onto acylhydrazonoyl chlorides (1a-c) (precursors of the reactive nitrile imine 1,3-dipolar species) to afford good yields of the corresponding 2-[(2-oxo-1-arylhydrazonopropan-1-yl)mercapto]benzoic acids (2a-c). The latter acyclic adducts, in THF in the presence of 1,1'-carbonyldiimidazole, undergo intramolecular cyclization involving the activated carboxy and the enol functionality to deliver the respective 2-(N-arylhydrazono)-3-oxobenzothiophenes (3a-c). In the solid state, the latter compounds adopt the (Z)-geometry around the C=N double bond as evidenced by single crystal X-ray structure determination for 3b. 相似文献
2.
Jalal A.?Zahra Bassam Abu?Thaher Mustafa M.?El-Abadelah Hans-Hartwig?OttoEmail author 《Monatshefte für Chemie / Chemical Monthly》2005,136(4):567-570
Summary. Nitrilimines prepared from N-arylhydrazono chlorides reacted with 2-mercaptonicotinic acid yielding the corresponding addition products, 2-[(2-oxo-1-arylhydrazonopropan-1-yl)mercapto] nicotinic acids, which were treated with 1,1-carbonyldiimidazole in THF affording by cyclocondensation the corresponding hitherto unknown 2-arylhydrazono-3-oxothieno[2,3-b]pyridines. 相似文献
3.
Proton NMR was used to study the complexation reaction between silver ion and hexathia-18-crown-6 in a number of binary mixed solvents of dimethyl sulfoxide with acetonitrile and methanol. Formation constants for the resulting 1:1 complexes in different solvent mixtures were determined by computer fitting of the chemical shift-mole ratio data. The influence of solvent composition on the stability of the resulting complex is discussed. The exchange kinetics of Ag+-hexathia-18-crown-6 in 70-30 wt.% dimethyl sulfoxide-acetonitrile and 75-25 wt.% dimethyl sulfoxide-methanol were studied by proton NMR line-shape analysis. In both solvent mixtures, the exchange of thiacrown ether between the free and complexed sites was found to proceed via a dissociative pathway. The exchange rates and the activation parameters E
a, H
, S, and G for the ligand exchange were determined and the influence of solvent properties on these parameters discussed. 相似文献
4.
Jouyban A Khoubnasabjafari M Vaez-Gharamaleki Z Fekari Z Acree WE 《Chemical & pharmaceutical bulletin》2005,53(5):519-523
Applicability of the Jouyban-Acree model for calculating absolute viscosity of binary liquid mixtures with respect to temperature and mixture composition is proposed. The correlation ability of the model is evaluated by employing viscosity data of 143 various aqueous and non-aqueous liquid mixtures at various temperatures collected from the literature. The results show that the model is able to correlate the data with an overall percentage deviation (PD) of 1.9+/-2.5%. In order to test the prediction capability of the model, three experimental viscosities from the highest and lowest temperatures along with the viscosities of neat liquids at all temperatures have been employed to train the model, then the viscosity values at other mixture compositions and temperatures were predicted and the overall PD obtained is 2.6+/-4.0%. 相似文献
5.
Talebi M Ghassempour A Talebpour Z Rassouli A Dolatyari L 《Journal of separation science》2004,27(13):1130-1136
A simple and rapid microwave-assisted extraction (MAE) procedure was developed and optimized for the extraction of paclitaxel (Taxol) from the needles of yew trees Taxus baccata L. grown in Iranian habitats. The samples, immersed in a methanol-water mixture, were irradiated with microwaves in a closed-vessel system. The method was evaluated using a factorial design approach based on parameters such as extraction time, temperature, methanol concentration in water (v/v), and the ratio of grams of sample to 10 mL of solvent. Statistical treatment of the results revealed that the selected parameters were all significant except the extraction time. Optimum conditions would be 1.5 g samples in 10 mL solvent (90% methanol), an extraction temperature of 95 degrees C, and an extraction time of 7 min. The extracts has been analyzed by reverse-phase high-performance liquid chromatography with UV detection (LC/UV) at 227 nm for quantification. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used for confirmation. The main advantage of the proposed MAE method versus conventional solvent extraction (CSE) are the considerable reductions in time (7 min versus 16 h) and in solvent consumption (20 mL versus 150 mL). The MAE procedure yielded extracts that could be analyzed directly without any preliminary clean-up or solvent exchange steps. Both extraction methods show RSDs lower than 10% and lead to comparable recoveries of paclitaxel (87-92%). 相似文献
6.
Thorbjrn Vincent Snderby Zahra Najarzadeh Daniel Erik Otzen 《Molecules (Basel, Switzerland)》2022,27(13)
Functional amyloid is produced by many organisms but is particularly well understood in bacteria, where proteins such as CsgA (E. coli) and FapC (Pseudomonas) are assembled as functional bacterial amyloid (FuBA) on the cell surface in a carefully optimized process. Besides a host of helper proteins, FuBA formation is aided by multiple imperfect repeats which stabilize amyloid and streamline the aggregation mechanism to a fast-track assembly dominated by primary nucleation. These repeats, which are found in variable numbers in Pseudomonas, are most likely the structural core of the fibrils, though we still lack experimental data to determine whether the repeats give rise to β-helix structures via stacked β-hairpins (highly likely for CsgA) or more complicated arrangements (possibly the case for FapC). The response of FuBA fibrillation to denaturants suggests that nucleation and elongation involve equal amounts of folding, but protein chaperones preferentially target nucleation for effective inhibition. Smart peptides can be designed based on these imperfect repeats and modified with various flanking sequences to divert aggregation to less stable structures, leading to a reduction in biofilm formation. Small molecules such as EGCG can also divert FuBA to less organized structures, such as partially-folded oligomeric species, with the same detrimental effect on biofilm. Finally, the strong tendency of FuBA to self-assemble can lead to the formation of very regular two-dimensional amyloid films on structured surfaces such as graphite, which strongly implies future use in biosensors or other nanobiomaterials. In summary, the properties of functional amyloid are a much-needed corrective to the unfortunate association of amyloid with neurodegenerative disease and a testimony to nature’s ability to get the best out of a protein fold. 相似文献
7.
Leila Saedi Zahra Javanshir Salah Khanahmadzadeh Maryam Maskanati Milad Nouraliei 《Molecular physics》2020,118(7)
ABSTRACTDensity functional theory calculations were used to investigate the potential application of an AlN nanocluster in the detection of H2S, COS, CS2 and SO2 gases. In overall, the order of strength of interaction of these gases with the nanocluster is as follows: SO2 (Ead?=??17.6?kcal/mol)?>?H2S (Ead?=??14.0?kcal/mol)?>?COS (Ead?=??8.4?kcal/mol)?>?CS2 (Ead?=??4.5?kcal/mol). This indicates that by increasing the electric dipole moment, the adsorption energy becomes more negative. We found that the Al12N12 nanocluster may be a promising work function-type sensor for SO2 gas among the studied gases. Also, it is an electronic sensor for both SO2 and CS2 gases but selectively acts between them because of their different effects on the electrical conductivity. It is neither work function-type nor electronic sensor for H2S and COS gases. The AlN nanocluster benefits from a short recovery time about 7.7?s and 18.0?ms for desorption of SO2 and CS2 gases from its surface at room temperature, respectively. It is also concluded that this cluster can work at a humid environment. 相似文献
8.
Mohammad Reza Islami Zahra Hassani Hassan Sheibani 《Phosphorus, sulfur, and silicon and the related elements》2013,188(11):2547-2554
Phthalimide or succinimide undergo a reaction with dialkyl acetylenedicarboxylates and triphenylphosphine to produce highly-functionalized stable heterocyclic phosphorus ylides in good yields in water-tetrahydrofuran (6:1). This methodology is of interest because of the use of water as solvent, thus minimizing the cost, operational hazards, and environmental pollution. 相似文献
9.
10.
Ashkan Madadlou Zahra Emam-Djomeh Mohamad E. Mousavi Mohamadamin Mohamadifar Mohamadreza Ehsani 《Ultrasonics sonochemistry》2010,17(1):153-158
Casein gels were made from solutions sonicated by 24 and 130 kHz ultrasounds for 0, 60 and 120 min, followed by acidification with glucono-δ-lactone at 30 °C. The dynamics of gel formation were studied using rheological methods and microstructure of gels was monitored using scanning electron microscopy. Sonication postponed the gelation point to a lower pH value and increased the elasticity of freshly formed gels. It also resulted in gels with a more interconnected structure and smaller non-distinguishable particulates. This structure was especially dominant for the gel made from the solution already sonicated for 120 min. 相似文献