Activity and selectivity of Ni nanoclusters in the selective hydrogenation of acetylene: A computational investigation

In this work, the Ni_n (n = 2–10) nanoclusters were investigated to design new catalysts for the selective hydrogenation of acetylene. Our results show that among the Ni_n nanoclusters, the Ni₆ nanocluster can be used as a catalyst in the reactions of hydrogenation. In the presence of the Ni₆ nanocluster, the E_a of the forward step in the reaction of conversion of vinyl to ethylene was 21.21 kJ/mol lower than that of the reverse step in the reaction of conversion of acetylene to vinyl. Also, the E_a of the forward step in the reaction of conversion of ethyl to ethane was 96.59 kJ/mol higher than that of the reverse step in the reaction of conversion of ethylene to ethyl. According to the obtained results, the Ni₆ nanocluster can selectively act in the hydrogenation of a mixture of acetylene and ethylene.     

Water as a Green Solvent for Fast and Efficient Reduction of Carbonyl Compounds with NaBH4 under Microwave Irradiation

Reduction of varieties of carbonyl compounds such as aldehydes, ketones, α,β‐unsaturated aldehydes and ketones, α‐diketones and acyloins was carried out very fast and efficiently by sodium borohydride in water under microwave irradiation. The corresponding product alcohols were obtained in high to excellent yields.     

Electro‐Oxidation of 3,4‐Dihydroxybenzoic Acid in the Presence of 6‐Methyl‐1,2,4‐Triazine‐3‐Thione‐5‐One: Unique Synthesis of 7H‐Thiazolo[3,2‐b]‐1,2,4‐Triazin‐7‐One Derivative in Aqueous Media

The electrochemical oxidation of 3,4‐dihydroxy benzoic acid ( 1 ) has been studied in the presence of 6‐methyl‐1,2,4‐triazine‐3‐thione‐5‐one ( 2 ) in aqueous solution. The oxidation mechanism of 1 and its reaction in the presence of 2 was offered. It was confirmed that 1 is converted to 7H‐thiazolo[3,2‐b]‐1,2,4‐triazin‐7‐one derivative 5 through Michael addition reaction of 2 to anodically generated o‐benzoquinone. The results of the research were used for electrochemical synthesis of 5 in an undivided cell in good yield and purity.     

Effect of preparation methods of graphene oxide on permeability of free-standing membranes against polar and nonpolar species

ABSTRACT

In this study, graphene oxide (GO) was synthesized using Hummers, modified Hummers and improved Hummers methods, and then freestanding membranes were prepared based on these materials. Effects of different GO preparation methods on C/O ratio and interlayer spacing of freestanding membranes were studied. Structure of these membranes was studied by X-ray diffraction, contact angle, XRF, FT-IR, and FESEM methods. Also, permeability of ammonia, dichloromethane, and water vapor was investigated through these membranes. Results showed that, the sample prepared by the Hummers method had lower C/O ratio, smoother surface and lower permeability for polar species, such as water and ammonia vapors, than nonpolar materials. Membranes prepared using Improved Hummers method showed the least permeability against nonpolar vapors such as dichloromethane.     

Preparation of Polyvinyl Acetate (PVAc) and PVAc–Ag–Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> Composite Nanofibers by Electro-spinning Method

Magnetite (Fe₃O₄) and silver nanoparticles were synthesized via simple chemical reactions at room temperature. Poly vinyl acetate (PVAc) nano-fibers and their nanocomposites with Ag and Fe₃O₄ were prepared by electro-spinning method. Effect of various electric potentials and distance on the morphology and diameter of fibers were investigated. Photocatalytic properties of silver in degradation five different dyes as organic pollutants in water were investigated. Fe₃O₄ nanoparticles exhibit a super-paramagnetic behavior at room temperature. Nontoxic nanoparticles appropriately enhanced both thermal stability and flame retardant property of the PVAc matrix. In the presence of flame, Fe₃O₄ nanoparticles remain together (show resistance to drip falling because of magnetic interaction) and build a barrier against flame.     

Mimetic Attractors

In this paper,we investigate the mathematical modeling for the cosmological attractors propagated in mimetic gravity upon which an interacting dark energy-dark matter is supposed to be existed. The average value of the interaction of these percentages, namely Γ_i say, may be used to investigate generally the modeling of an attractor; the actual value could only be determined by data in any particular case. We have seen, for example, that it was led to investigate the subject of initially invariant submanifolds.     

Sulfonic acid-functionalized titanomagnetite nanoparticles as recyclable heterogeneous acid catalyst for one-pot solvent-free synthesis of 3,4-dihydropyrimidin-2(1<Emphasis Type="Italic">H</Emphasis>)-ones/thiones

Sulfonic acid-functionalized titanomagnetite (Fe_3?x Ti _x O₄@SO₃H) nanoparticles were prepared by grafting sulfonic acid groups on Fe_3?x Ti _x O₄ nanoparticles. This new heterogeneous acid nanocatalyst demonstrated an efficient catalytic performance in the one-pot synthesis of dihydropyrimidin-2(1H)-one/thione derivatives under solvent-free conditions with high yields. The nanocatalyst could easily be separated from the reaction mixture simply by using an external magnet, recycled and reused for several times with no significant loss of catalytic activity. These nanoparticles were characterized by different physicochemical techniques, such as Fourier transform infrared, scanning electron microscopy, energy-dispersive X-ray analysis, thermogravimetric and vibrating sample magnetometer (VSM) analyses.     

Electrochemical synthesis of 4-(dihydroxyphenylthio)-2H-chromen-2-one derivatives

The 4-(dihydroxyphenylthio)-2H-chromen-2-one derivatives have been synthesized by direct electrochemical oxidation of catechols in the presence of 4-mercaptocoumarin as a nucleophile in water/acetonitrile (50/50) solution, in a one-pot process, at carbon rod electrode, in an undivided cell and in constant current conditions, through an EC mechanism. The products are characterized by spectra data. Besides, the difference in electrochemical oxidation of catechol in the presence of 4-hydroxycoumarin and 4-mercaptocoumarin explained by computational structure, natural bond orbital (NBO) analysis and density functional theory (DFT: B3LYP/6-31G*//B3LYP/6-31G*) based methods, using the GAUSSIAN 98 package of programs.     

One‐pot and green synthesis 1H-pyrazolo[1,2-b]phthalazine-5,10-dione and dihydropyrano[3,2-c]chromene derivatives by Fe3O4@SiO2-imine/phenoxy-Cu(II) as an efficient and reusable catalyst

In the current study, magnetite-silica core–shell nanoparticles modified with Cu-salen complex (Fe₃O₄@SiO₂-imine/phenoxy-Cu(II)) was utilized as a heterogeneous catalyst for the one-pot multicomponent synthesis of 1H-pyrazolo[1,2-b]phthalazine-5,10-dione and dihydropyrano[3,2-c]chromene derivatives under solvent-free conditions, without using any harmful organic reagents/solvent. The current synthetic protocol demonstrates that the reactions proceeds to completing step, leading to the successful synthesis of high purity compounds. Advantages of this method include easy purification, reusability of the catalyst, green and mild procedure and synthesis of new derivatives in high yields within short reaction time.