Tài liệu miễn phí Hoá học
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Modification of biomass-derived activated carbon with magnetic α-Fe2O3 nanoparticles for CO2 and CH4 adsorption
Magnetic and nonmagnetic activated carbons (ACs) were successfully prepared by using AC obtained from spent coffee grounds (SCGs) for use in CO2 and CH4 capture. SCGs were activated by chemical activation to produce ACs and a magnetic α-Fe2O3/AC composite was prepared by coprecipitation method from the ACs produced. Magnetic and nonmagnetic samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and energy dispersive X-ray spectrometry (EDX) techniques. The textural properties of samples were determined by nitrogen adsorption-desorption using the Brunauer–Emmett–Teller (BET) and Barrett–Joyner–Halenda (BJH) methods.
4/3/2023 10:42:11 PM +00:00
Synthesis and antitumor activities of 2-(piperidin-4-yl)-thiazole-4-carboxamides analogues of tubulysins
Tubulysins are a family of natural products that exhibit potent antitumor activities, which have attracted much attention from synthetic and medicinal chemists. Previous attempts to aromatize the Tuv part of tubulysin analogues led to a loss in antitumor activity, which suggested that the Ile and Tuv fragments of these analogues were adopting different conformations than the natural products. In this study, a series of 2-(piperidin-4-yl)-thiazole-4- carboxamides have been prepared to investigate whether an intramolecular H-bond between key NH and OH groups is responsible for the conformational control.
4/3/2023 10:41:43 PM +00:00
Investigation of sulfuric acid-treated activated carbon properties
A granulated type of commercial activated carbon (GAC) with surface area of 828 m2/g was treated with a strong solution of sulfuric acid (98% wt.) at a temperature of 30°C. The physicochemical and porous properties and the surface chemistry of the sorbents were investigated and compared in detail. It was established that the lower temperatures of impregnation and the higher concentration of H2SO4 solution resulted in the introduction of higher percentages of sulfur-containing groups and smaller porosity loss. The results of EDS, FTIR, and XPS tests confirmed the introduction of sulfone groups and acidic oxygenated ones, which increased the adsorbent affinity towards mercury species available in the aqueous phase (pH 7) by 20%.
4/3/2023 10:41:26 PM +00:00
Intermolecular complexes of halocyclopropenone derivatives with the hypohalous acids HOF, HOCl, HOBr, and HOI
The intermolecular interactions between halocyclopropenone derivatives (HC3OX; X = I, Br, Cl, and F) and hypohalous acids (HOY; Y = I, Br, Cl, and F) were studied via the MP2 method utilizing the aug-cc-pVTZ and aug-cc-pVTZ(-PP) basis sets. The three types of complexes were hydrogen bonds, halogen bonds, and complexes containing both hydrogen and halogen bonds. The results obtained indicated that interactions in the Type 1 complexes were stronger than those in Types 2 and 3. The H–O bonds revealed red shifts with complex formation in Types 1 and 2. The O–Y bonds displayed red shifts in the Type 3 and blue shifts in the Type 2 structures.
4/3/2023 10:41:14 PM +00:00
The effect of washing on stabilized and unstabilized low-density polyethylene films naturally weathered in a sub-Saharan region (Ghardaïa, Algeria)
The effect of washing stabilized and unstabilized blown extruded films of low-density polyethylene (LDPE) used for greenhouse coverings naturally weathered in a sub-Saharan facility at Ghardaïa (Algeria) for 19 and 6 months, respectively, was studied. A comparison between unwashed and daily washed samples was done. The changes in the films’ properties were followed at regular intervals using various characterization methods (physicochemical and mechanical). Although in both cases the chemical species formed due to the weathering were qualitatively the same, they essentially differed in their concentrations, namely they were higher for the washed samples than for the unwashed ones.
4/3/2023 10:41:03 PM +00:00
An exploration of new avenues regarding deep tissue penetration and higher singlet oxygen efficiencies: novel near-IR photosensitizers for photodynamic therapy
A series of novel BODIPY-bearing electron-withdrawing groups at the meso position are reported here. According to the optical measurements, it may be clearly seen that the introduction of electron-donating groups into 3,5-positions and the presence of electron-withdrawing groups at the meso position of the BODIPY core resulted in spectacular bathochromic shifts (up to ~ 304nm), and the projected photosensitizers had absorption bands in the therapeutic window of the electromagnetic spectrum (600–900nm). The absorption maxima of compounds 4, 5, 6, and 7 were at 886nm, 890nm, 760nm, and 761nm, respectively.
4/3/2023 10:40:51 PM +00:00
Chiral 1,4-aminoalkylphenols for enantioselective diethylzinc addition to aldehydes
Starting from a chiral secondary alcohol, novel enantiopure 1,4-aminoalkylphenols (AAPs) were prepared by exploiting conventional organic transformations such as the Mitsunobu reaction, Eschweiler–Clarke N -methylation, and demethylation of anisoles. The catalytic activity of the 1,4-AAPs was investigated in enantioselective Et2Zn addition to benzaldehyde. They were found to accelerate the Et2Zn addition to benzaldehyde. High yields and enantioselectivities (e.g., 95% yield and 82% ee) were achieved.
4/3/2023 10:40:40 PM +00:00
A case study of antiaromaticity: Carbomethoxy cyclopropenyl anion
The simplest ideas of antiaromaticity refer to regular monocyclic systems and the eigenfunctions of the Hückel Hamiltonian for 4n π electrons in such systems. The antiaromaticity is expressed in the energy penalty for such idealized systems relative to the Hückel energy for 2n noninteracting π pairs. Observed systems seldom achieve the regular planar geometry assumed in this picture, owing to their ability to ease the antiaromaticity penalty by departures from the regular geometry and also by export of the 4n π electrons’ charge to substituents. In this report we estimate numerical values for the stabilization derived from such departures from the structure and the charge distribution of the idealized antiaromatic cyclopropenyl anion for a specific case, 3-dehydro-3-methyl carboxylate cyclopropenyl anion 1(–) using the thermochemical scheme CBSQB3 supplemented by CCSD(T) calculations.
4/3/2023 10:40:17 PM +00:00
Preparation of epoxidized sunflower oil metal soap derivatives and their use as heat stabilizers for polyvinyl chloride
The aim of this work was to prepare metal soaps of epoxidized sunflower oil (ESO) and use them as thermal stabilizers for polyvinyl chloride (PVC). For that purpose, commercial sunflower oil was first epoxidized and then used to prepare (Ba, Zn, Pb, and Cd) metal soap derivatives, which were characterized by Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The prepared metal soaps derivatives of ESO were used as thermal stabilizers for plasticized PVC. Discoloration, residual thermal stability at 200°C, and rheological properties of PVC samples were tested.
4/3/2023 10:40:07 PM +00:00
Organotemplate-free Cs-ABW nanozeolite as highly reactive and recyclable catalyst for Henry reaction between benzaldehyde and nitroethane
Zeolite Cs-ABW nanocatalyst has been hydrothermally synthesized without using any harmful organic template. The zeolite nanocrystal with very high solid yield (81.88%) can be obtained within 60 min and at 180°C (~20 atm), conditions that are much faster and gentler than the existing synthesis methods. The orthorhombic Cs-ABW nanocrystals (mean size of 32 nm) have high aluminum content (Si/Al ratio = 1.14) and possess high basicity. The nanocrystals also exhibit better catalytic activity than conventional homogeneous catalysts in the Henry (nitroaldol) reaction of benzaldehyde with nitroethane under microwave heating conditions.
4/3/2023 10:39:46 PM +00:00
Synthesis, crystal structure, and characterization of two heterometallic transition metal citrate complexes [M = Co(II) and Cd(II)]
In this study, two heterometallic transition metal complexes with the formulas [CoK4(µ10-C6H5O7)2]n and [CdK(µ8-C6H5O7)(µ-H2O)(H2O)]n were synthesized as crystalline compounds. The structures of these crystalline metal complexes were characterized by their spectral analyses (FT-IR, FT-Raman, thermal analysis, magnetic properties, and single-crystal X-ray diffraction techniques). According to the spectral data of the new metal complexes obtained, both metal complexes are in the monoclinic crystal system and in the P21/c and P21 space groups, respectively.
4/3/2023 10:39:31 PM +00:00
A fast and convenient analysis method for the determination of cations in pomegranate juices by capillary electrophoresis with contactless conductivity detection
Health beneficial effect of pomegranate is mainly due to its confirmed high antioxidant capacity and polyphenolic content. In recent years, experimental and clinical studies have shown that pomegranate intake lowers blood pressure. Potassium and other minerals such as calcium and magnesium may be responsible for this property. In this study, a rapid, economic, reliable, and applicable capillary electrophoresis method was proposed with contactless conductivity detection for the quantitative determination of six cations in different pomegranate juices.
4/3/2023 10:39:24 PM +00:00
Design, synthesis, and evaluation of the antimycobacterial activity of 3-mercapto-1,2,4-triazole–pyrrole hybrids
A series of 3-mercapto-1,2,4-triazole–pyrrole hybrids was designed as antimycobacterial agents by employing 5- (4-(1H -pyrrol-1-yl)phenyl)-4H -1,2,4-triazole-3-thiol as the scaffold onto which several types of moieties were introduced in the triazole ring at N-4 and N-2 and as substituents of the mercapto function. The aforementioned moieties are an allyl or a phenyl moiety at N-4; an aminomethyl group at N-2; or methyl, substituted benzyl, ethoxycarbonylmethyl, or substituted phenacyl at sulfur. Investigation of the compounds in the resulting library as growth inhibitors of Mycobacterium smegmatis showed that their minimum inhibitory concentration was higher than 64 mg/L.
4/3/2023 10:39:17 PM +00:00
Pore length- and ion concentration-dependent ionic current in cylindrical nanopores: An atomistic molecular dynamics study
The sensing of individual molecules as they pass through nanopores under an external field is a popular research field. The approach is simply based on the detectable temporary blockades in the ionic current as the molecules pass through the nanopores. These signatures of the current have been shown to be a function of nanoparticle and nanopore size and geometry as well as the external electric field. However, models developed in this context fail to predict the experimentally observed behavior in technologically important shorter nanopores.
4/3/2023 10:38:59 PM +00:00
Investigation of the ideal composition of metal hexacyanocobaltates with high water oxidation catalytic activity
The electrocatalytic activities of Prussian blue analogues (PBAs) have recently received much attention due to their robustness and efficiency. Considering that PBAs with hexacyanocobaltate building block stand forward among other PBAs, a systematic study on a family of metal hexacyanocobaltates is presented in this study. Metal hexacyanocobaltates (M = Co, Mn, Ni, and Fe) were prepared, characterized, and electrochemical studies were performed. A series of mixed-metal cobalt-iron hexacyanocobaltates has also been studied to determine the ideal composition of a metal hexacyanocobaltate for electrocatalytic water oxidation process.
4/3/2023 10:38:47 PM +00:00
Synthesis, kinetic study, and reaction mechanism: Nucleophilic substitution reactions of butyl methyl chlorophosphate with substituted anilines and deuterated substituted anilines in acetonitrile
This study demonstrated the kinetics of nucleophilic substitution reactions of butyl methyl chlorophosphate (2) with X-anilines (XC6H4NH2) and deuterated X-anilines (XC6H4ND2) in MeCN at 55.0 ± 0.1°C together with the general optimized method for the synthesis of 2 under mild conditions. Different spectroscopic characterizations revealed the formation of 2 with high purity. The free energy relationship with the substituents X in the anilines exhibited biphasic concavity upwards with a break point at X = H, which induced large negative ρX and small positive βX values.
4/3/2023 10:38:06 PM +00:00
Removal of Cr(VI) from wastewater through glycine assisted synthesis of TiO2
In this study, titanium dioxide was synthesized via solution combustion method. Titanium(IV) oxysulfate was used as a titanium source. The fuel type, reaction time, and reaction temperature were tested for optimization. The glycine was set as a suitable fuel. Structural properties of the final product were characterized by p-XRD. Scanning electron microscopy (SEM) and BET techniques were used to examine the morphology. The synthesized products were compared to the commercial TiO2 and it was found that the titanium dioxide with the high surface area (63.628 m2/g) has been successfully synthesized by solution combustion method with time and energy saving.
4/3/2023 10:37:55 PM +00:00
Fuel characteristics and combustion behavior of seaweed-derived hydrochars
In this study, conversion of seaweeds into hydrochars was investigated with the aim of obtaining a renewable energy feedstock. The seaweeds Fucus serratus and Alaria esculenta, and a mixture of seaweeds, mainly consisting of Cystoseria sp. and Laurencia sp., were subjected to hydrothermal carbonization (HTC) in subcritical water at three different temperatures: 200, 225, and 250 °C. Fuel characteristics and chemical properties of the derived hydrochars were determined using the standard fuel analysis and spectroscopic methods. The combustion behavior of seaweeds and hydrochars was examined via nonisothermal thermogravimetric analysis under air atmosphere. The seaweed-derived hydrochar yields were lower than those of the lignocellulosic-derived hydrochar yields in the literature.
4/3/2023 10:37:42 PM +00:00
Boric acid as an efficient and green catalyst for the synthesis of 2-amino-4,6-diarylnicotinonitrile under microwave irradiation in solvent-free conditions
Microwave irradiation has been used to improve the one-pot synthesis of substituted 2-amino-4,6-diarylnicotinonitrile in the presence of boric acid as an efficient and green catalyst under solvent-free conditions within 48–60s. All the analogs that have not been reported previously were characterized by their melting points, IR, 1H NMR, and 13C NMR spectra. One of the structures was verified by the analysis of a single crystal. The reported synthetic procedure provided remarkable advantages such as short reaction times, excellent yield, facile workup, and the use of a green catalyst.
4/3/2023 10:37:21 PM +00:00
Synthesis and characterization of polycaprolactone-based segmented polyurethanes
Segmented polyurethanes were synthesized by the reactions of poly(ε-caprolactone) (PCL)-diol and 1,6- hexamethylene diisocyanate through bulk polymerization without using solvent, initiator, or catalyst. Phase separation and hydrogen bond formation between hard segments or between hard and soft segments were examined by Fourier transform infrared spectroscopy (FTIR)-ATR and X-ray diffraction (XRD), while physical and mechanical properties were studied by atomic force microscope, differential scanning calorimeter, dynamic mechanical analysis, and tensile tester.
4/3/2023 10:37:10 PM +00:00
Acid-activated clay as heterogeneous and reusable catalyst for the synthesis of bioactive cyclic ketal derivatives
A new heterogeneous acid catalyst based on a natural resource, Tunisian clay (Clay-H0.5), has been prepared and characterized by FT-IR, FE-SEM, and powder X-ray diffraction (XRD), as well as chemical composition, cation exchange capacity, specific surface area, and pore volume. Acid treatment for 0.5 h enlarged the surface area from 78.24 to 186.10 m2/g and pore volume (PV) from 0.186 to 0.281 cm3/g. The catalytic activity of this material was investigated in ketalization reaction under mild solvent-free conditions. This achieved up to 92% isolated yield for only 10 wt.% of the catalyst. This environmentally friendly method has advantages such as simple work-up procedure, avoidance of organic solvents, and good performance in ketalization reactions.
4/3/2023 10:37:02 PM +00:00
Biodegradability study of polypropylene fibers blended with disposable recycled poly(lactic acid) plastic flakes
Polymer blending as an efficient method for blending at least two polymers is usually used to create new materials with desirable physical properties. This article focuses on the biodegradability evaluation of polypropylene (PP) fibers modified with disposable recycled poly(lactic acid) (r-PLA) plastic flakes. Biodegradable modified PP fibers containing 30% r-PLA were prepared by melt spinning process and evaluated with different methods of biodegradation assays. The soil burial test method, CO2 evolution analysis, weight loss, mechanical properties, and average molecular weight measurements and analysis of surface morphological changes were performed for biodegradability evaluation of the modified PP fibers.
4/3/2023 10:36:50 PM +00:00
Spectrophotometric methods for the determination of fluoride ion using indole-3-acetic acid interaction with iron(III)
This study is related to the determination of fluoride ion by the conversion of pink-colored Fe(III) and indole3-acetic acid (IAA) into a colorless hexafluoride ferrite complex with the addition of fluoride. The optimum conditions of the complex formation were found to be pH 1.7 and a temperature of 60 °C. The maximum absorption wavelength of the complex and the detection limit of the method were 525 nm and 0.26 mg/L, respectively. The interfering effects of the different cations (Ag+, Al3+, Ba2+, Ca2+, Cd2+, Co2+, Cu2+, K+, Mg2+, Na+, Ni2+, Pb2+) and anions (SO2−4, SO2−3, NO−2, I−, Br−, Cl−, SCN−, CH3COO− , H2PO−4, ClO−4) were also investigated.
4/3/2023 10:36:42 PM +00:00
New flavonoid glycosides conjugates: Synthesis, characterization, and evaluation of their cytotoxic activities
A series of novel halogenated 3-hydroxyflavones (3HFs) were prepared by reacting halogenated hydroxyacetophenones with the appropriate aromatic aldehyde. Glycosylation of 3HFs with acetobromoglucose and deprotection of the acetyl protective groups afforded the desired 3-O-flavonoids glycosides in satisfactory yields. All the prepared compounds were tested for their cytotoxic activity against HCT-116, MCF-7, and OVCAR-3 human cancer cell lines. The 3HFs exhibited higher cytotoxic activities compared with the glycosylated flavonoids. Overall, the structure-activity relationship study showed that the introduction of glycoside moiety at the C-3 OH position does not improve the bioactivity.
4/3/2023 10:36:30 PM +00:00
Why protein conformers in molecular dynamics simulations differ from their crystal structures: A thermodynamic insight
Conformers generally deviate structurally from their starting X-ray crystal structures early in molecular dynamics (MD) simulations. Studies have recognized such structural differences and attempted to provide an explanation for and justify the necessity of MD equilibrations. However, a detailed explanation based on fundamental physics and validation on a large ensemble of protein structures is still missing. Here we provide the first thermodynamic insights into the radically different thermodynamic conditions of crystallization solutions and conventional MD simulations. Crystallization solution conditions can lead to nonphysiologically high ion concentrations, low temperatures, and crystal packing with strong specific protein–protein interactions, not present under physiological conditions.
4/3/2023 10:36:19 PM +00:00
Progress in the chemistry of 3-amino-9-ethylcarbazole
Generally, 3-amino-9-ethylcarbazole is considered a versatile compound not only for its unique electronic properties but also for its significance as a building block in synthetic, pharmaceutical, and material chemistry. The synthesis, chemical reactivity, and applications of 3-amino-9-ethylcarbazole are described in this review. The presence of the amino group at position 3 exhibits a unique reactivity with both C-2 and C-4. The reactions of 3-amino-9- ethylcarbazole are divided into three categories, reactions that involve the amino group and cyclization reactions that involve the amino group and C-2 and/or C-4. In this review, relevant and appropriate applications of the synthesized, isolated, and condensed carbazole derivatives are reported.
4/3/2023 10:36:09 PM +00:00
Preparation of α-hydroxyphenylacetic acid with cyclodextrins as an effective phase-transfer catalyst and its reaction mechanism
An effective procedure for the synthesis of α-hydroxyphenylacetic acid with cyclodextrin (CD) catalysts was developed. The phase-transfer catalyst types, catalyst loadings, reaction times, reaction temperatures, and substrate molar ratios were investigated to optimize the reaction conditions. In addition, the factors that affect the reaction were studied, and the relationship between benzaldehyde and β -cyclodextrin (β -CD) was analyzed through 2D-ROESY. The equilibrium constant when β -CD was used as the catalyst was calculated. The results indicated that β -CD is the optimal catalyst for the reported reaction (yield: 69.08%). Furthermore, the mechanism underlying the reported reaction was proposed.
4/3/2023 10:35:57 PM +00:00
Chemistry of endemic Tanacetum mucroniferum Hub.-Mor. & Grierson extracts and three new sesquiterpene lactones
Tanacetum mucroniferum Hub.-Mor. & Grierson was collected from Sakaltutan in Erzincan Province of Turkey. Comparative phytochemical investigation was carried out on the ethyl acetate and methanol extracts of the plant. The secondary metabolites were isolated and purified by chromatographic methods such as column chromatography, medium pressure liquid chromatography, high-performance thin-layer chromatography, and preparative thin-layer chromatography. The extracts of the aerial parts of Tanacetum mucroniferum yielded three new sesquiterpene lactones and some known compounds, namely two sesquiterpene lactones, six flavonoids, three coumarins, and one triterpene.
4/3/2023 10:35:50 PM +00:00
Computational investigation of influenza A virus M2 protein inhibition mechanism by ion channel blockers
The M2 protein of the influenza A virus, responsible for flu, is a homotetramer transmembrane protein, forming a transmembrane ion channel, where His 37s act as pH sensors and Trp 41s and Asp 44s act as channel gates. Opening of this channel leads to transfer of virus RNA into the human host. Thus, blocking this transfer is an important pharmaceutical strategy to stop infection. As a result of viral drug resistance, commercially available channel inhibitors, rimantadine (RIM) and amantadine (AMA), are not as effective as they used to be. Understanding binding sites and outcomes of binding will lead to new inhibitor design studies.
4/3/2023 10:35:28 PM +00:00
Plasma polymerized linalool (ppLin): An antimicrobial and biocompatible coating
Bacterial infections in medical devices and drug resistance of bacteria can cause chaos in the world due to loss of lives in addition to the cost of device revisions, quarantine, disinfection of infected areas, and patient treatment. Antibacterial coatings of essential oils on medical devices can prevent bacterial attachment and reduce costs. Linalool is an antibacterial constituent of essential oils. Herein, we examine for the first time the fabrication and characterization of radio frequency (RF) plasma polymerized hydrophilic thin films from linalool (ppLin) by varying deposition parameters (RF power and deposition time) and the behavior of ppLin with two bacteria (Escherichia coli and Staphylococcus aureus) commonly related to microbial contamination of medical devices.
4/3/2023 10:35:06 PM +00:00