Green and catalyst-free synthesis of aminoanthraquinone derivatives in solvent-free conditions

In this study, new derivatives of aminoanthraquinone have been synthesized via one-pot three-component condensation reaction of 1- and 2-amino anthraquinones, triethyl orthoformate and CH-acid compounds without using any solvent or catalyst in mild temperature (50 °C). This simple and efficient method yields the desired products in short reaction time (14–50 min) and good to excellent yields (85–96%). Moreover, chemical structures of synthesized products have been entirely confirmed by FT-IR, ¹H and ¹³CNMR and mass spectroscopy and melting points.

     

Synthesis and characterization of a novel supported N-piperidine sulfamic acid on magnetic nanoparticles as a nanocatalyst for synthesis of pyrimido[4,5-c]pyridazines derivatives under ambient conditions and theoretical study on the mechanism using a DFT method

Research on Chemical Intermediates - In this study, magnetic nanoparticles (Fe3O4 NPs) were employed as good support for N-piperidine sulfamic acid to prepare a novel nanocatalyst...     

Automatic piloting in progressive dies using medial axis transform

Nowadays, progressive dies have a special role in various methods of sheet metal production. The design process, however requires a considerable amount of time and expertise. During the last three decades, different concepts of Computer Aided Progressive Die Design (CAPDD) have been studied all around the world. CAPDD involves various activities and among them piloting has been paid the least attention by researchers. In this paper, a mathematical model based on Medial Axis Transform (MAT) is introduced. This model is applicable to parts without suitable circular holes for direct piloting. The model analyzes the part geometry in order to find the best position for semi-direct and indirect pilots. It also optimizes the piloting system using minimum scrap strategy. A prototype software is also developed to automatically design auxiliary holes on the scrap part of the strip for piloting purposes. The input to the software is nesting template of the workpiece, which is composed of line and arc segments, and the output is the piloting system. The model is demonstrated through several industrial examples.     

Hydrogen dissociation dynamics on precovered Pd surfaces: Langmuir is still right

A recent scanning tunneling microscopy study by Mitsui et al. [Nature (London) 422, 705 (2003)] challenged the well-accepted picture based on early studies of Langmuir that an ensemble of at least two empty, catalytically active sites is required for the dissociative adsorption; instead, aggregates of three or more vacancies should be necessary. We have performed the first ab initio molecular dynamics study of the adsorption dynamics on a precovered surface providing detailed insights into the coverage dependence of the adsorption probability. The simulations show that there is no need to refine the Langmuirian picture: A dimer vacancy is still sufficient to dissociate hydrogen provided the kinetic energy of the molecules is large enough to overcome the relatively small adsorption barrier. In addition, we elucidate further aspects of the dissociation dynamics at precovered surfaces.     

Two-step liquid phase microextraction combined with capillary electrophoresis: A new approach to simultaneous determination of basic and zwitterionic compounds

In this work, two-step hollow fiber-based liquid-phase microextraction procedure was evaluated for extraction of the zwitterionic cetirizine (CTZ) and basic hydroxyzine (HZ) in human plasma. In the first step of extraction, the pH of sample was adjusted at 5.0 in order to promote liquid-phase microextraction of the zwitterionic CTZ. In the second step, the pH of sample was increased up to 11.0 for extraction of basic HZ. In this procedure, the extraction times for the first and the second steps were 30 and 20 min, respectively. Owing to the high ratio between the volumes of donor phase and acceptor phase, CTZ and HZ were enriched by factors of 280 and 355, respectively. The linearity of the analytical method was investigated for both compounds in the range of 10-500 ng mL(-1) (R(2) > 0.999). Limit of quantification (S/N = 10) for CTZ and HZ was 10 ng mL(-1) , while the limit of detection was 3 ng mL(-1) for both compounds at a signal to noise ratio of 3:1. Intraday and interday relative standard deviations (RSDs, n = 6) were in the range of 6.5-16.2%. This procedure enabled CTZ and HZ to be analyzed simultaneously by capillary electrophoresis.     

Hybrid-DFT Study and NBO Analysis of the Stereoelectronic Interaction Effects (Associated with the Anomeric Effects) on the Conformational Properties of 2,3,5,6-Tetrahalo-1,4-dioxanes and Their Analogs Containing S and Se Atoms

NBO analysis and hybrid density functional theory–based method (B3LYP/6-311+G**) was used to study the anomeric effects (AE), dipole–dipole interactions, and steric repulsion effects on the conformational properties of 2,3,5,6-tetrahalo-1,4-dioxane [halo = F (1), Cl (2), Br (3)], 2,3,5,6-tetrahalo-1,4-dithiane [halo = F (4), Cl (5), Br (6)], and 2,3,5,6-etrahalo-1,4-diselenane [halo = F (7), Cl (8), Br (9)]. B3LYP/6-311+G** results revealed a strong axial preference in compounds 1–3. Gibbs free energy difference (G _eq–G _ax) values (e.g., ΔG _eq-ax) between the axial and equatorial conformations of compound 1 to compound 3 are 8.19, 3.86, and 3.13 kcal mol^?1, respectively, as calculated by the B3LYP/6-311+G** level of theory. On the other hand, the NBO analysis of donor–acceptor (bond–antibond) interactions revealed that the AE for compounds 1–3 are ?12.26, ?16.46, and ?18.11 kcal mol^?1, respectively. Contrary to the increase of the AE values from compound 1 to compound 3, the increase of the steric repulsions (e.g., 1,3-syn-axial repulsions) could fairly explain the decrease of the axial conformation stability in compounds 1–3 compared to their equatorial conformations. Further, the correlations between the AE, structural parameters, and conformational behavior of compounds 4–9 have been investigated.     

Unstable Displacement of Non-aqueous Phase Liquids with Surfactant and Polymer

In this paper, we study two-phase multicomponent displacement of two immiscible fluids in both homogeneous and heterogeneous porous media. In many applications such as enhanced oil recovery, fluid mixing and spreading can be detrimental to the efficacy of the process. Here, we show that when an initially immobile phase is being displaced by a finite-size slug of solvents (surfactant and polymer), viscous fingering significantly enhances mixing and spreading of solvents. These effects are similar to those caused by medium heterogeneity and lead to poor displacement efficiency. We first quantify the displacement efficiency subject to different mobility ratios, Peclet numbers, and levels of medium heterogeneity. We observe a non-monotonic behavior in displacement efficiency as a function of mobility ratio, indicating that although stable frontal interface is desirable, miscible viscous fingering on the rear interface will eventually disintegrate the solvents slugs and reduce the displacement efficiency. Then, we show that miscible viscous fingering developing on the rear interface of the chemical slug could be greatly suppressed when viscosity contrast is gradually decreased using exponential or linear functions, leading to 10% increase in displacement efficiency while using the same amount of chemicals. To elucidate this low displacement efficiency, we study the evolution of mixing, spreading, and interfacial length and show that while higher viscosity ratios are quite effective in mobilizing the initially immobile phase in 1D displacements, they are in fact detrimental in 2D unstable displacements since they enhance mixing and spreading of solvents.

     

Adsorption of phenolic compounds from aqueous solutions using carbon nanoporous adsorbent coated with polymer

Phenolic compounds are a widespread class of water pollutants that are known to cause serious human health problems; and the demand for effective adsorbents for the removal of toxic compounds is increasing.In this work adsorption of phenol, resorcinol and p-cresol on mesoporous carbon material (CMK-1) and modified with polyaniline polymer (CMK-1/PANI) has been investigated in attempt to explore the possibility of using nanoporous carbon as an efficient adsorbent for pollutants. It was found that CMK-1/PANI exhibits significant adsorption for phenolic derivatives. Batch adsorption studies were carried out to study the effect of various parameters like adsorbent dose, pH, initial concentration and contact time. From the sorption studies it was observed that the uptake of resorcinol was higher than other phenolic derivatives. Freundlich and Langmuir adsorption isotherms were used to model the equilibrium adsorption data for phenolic compounds.