The Participation of 3,3,3-Trichloro-1-Nitroprop-1-Ene in the [3 + 2] Cycloaddition Reaction with Selected Nitrile N-oxides in the Light of the Experimental and MEDT Quantum Chemical Study

The regioselective zw-type [3 + 2] cycloaddition (32CA) reactions of a series of aryl-substituted nitrile N-oxides (NOs) with trichloronitropropene (TNP) have been both experimentally and theoretically studied within the Molecular Electron Density Theory (MEDT). Zwitterionic NOs behave as moderate nucleophiles while TNP acts as a very strong electrophile in these polar 32CA reactions of forward electron density flux, which present moderate activation Gibbs free energies of 22.8–25.6 kcal·mol−1 and an exergonic character of 28.4 kcal·mol−1 that makes them irreversible and kinetically controlled. The most favorable reaction is that involving the most nucleophilic MeO-substituted NO. Despite Parr functions correctly predicting the experimental regioselectivity with the most favorable O-CCCl3 interaction, these reactions follow a two-stage one-step mechanism in which formation of the O-C(CCl3) bond takes place once the C-C(NO2) bond is already formed. The present MEDT concludes that the reactivity differences in the series of NOs come from their different nucleophilic activation and polar character of the reactions, rather than any mechanistic feature.

Zinc Oxide Nanoparticles Promoted Highly Efficient and Benign Synthesis of 3,4-Dihydropyrimidine-2(1H)-one/thione Derivatives

Using the synthetic potential of recyclable zinc oxide(ZnO) nanoparticles (NPs), a proficient, elegant, and rapid one-pot synthesis of a variety of 3,4-dihydropyrimidine-2(1H)-one/thione derivatives from the1,3-dicarbonyl compound, urea/thiourea, and various aromatic aldehydes havebeen unveiled in the present research. TheZnONPs were synthesized by theco-precipitation method. The powder X-ray diffraction method was employed for the determination of thecrystallite size of the synthesized ZnONPs.The hexagonal phase was obtained in the XRD pattern of the synthesized ZnO NPs with anaverage crystallite size of 25 nm.The current synthetic strategy offers excellent yields, a short reaction time, favorable reaction conditions, easy transformation, non-chromatographic product purification, and catalyst recyclability. Furthermore, the catalyst could be retrieved and reused without losing any of its catalytic activity. As a result, this elegant protocol is an adequate method fordihydropyrimidinone/thione synthesis.

Water Purification by Potassium Humate–C.I. Basic Blue 3 Adsorption-Based Interactions

Interactions of C.I. Basic Blue 3 with potassium humate in aqueous systems were investigated. Both the humic content and dye removal are of crucial significance in relation to water of a desired quality. Dye retention experiments demonstrated that potassium humate is an exceptionally efficient adsorbent. The effect of both the pH and temperature on the adsorption process was investigated. The temperature proved to only slightly influence the extent of dye sorption; contrarily, under mildly acidic conditions (pH = 4.0), the quantity of dye adsorbed was doubled on standing. At this pH value, interactions between the positively charged dye and the dissociated carboxyl groups of humic substances are encountered. This was also supported by the obedience of the experimental data to the pseudo-second-order kinetic model. Three adsorption models, i.e., Langmuir, Freundlich and BET, were fitted to the experimental data; the equilibrium adsorption conformed to the Langmuir and BET isotherm equations on the basis of electrostatic dye–humics interactions, while the fitting of the Freundlich model referred to the heterogeneities of humic substances attributed to their colloidal behavior. Thermodynamic quantities, i.e., enthalpy, entropy and free energy change in the adsorption, were calculated. The low ΔHadsθ values verify the negligible effect of the temperature on the adsorption; ΔSadsθ denotes a thermodynamically favorable reaction, and ΔGadsθ denotes a spontaneous process.

Technological stress in higher level students in San Luis Potosí

During 2020, in the face of the recession caused by the COVID19 pandemic, public and private sectors suffer massive losses that force them to promote strategies for immediate reactivation. Education in México, despite estimating a considerable lag, had a favorable reaction towards "online classes” in all education levels. Through technological resources, administrative, teachers, parents and students were involved without having the opportunity to be questioned. As a result of this, a study was proposed with a quantitative approach and descriptive method, to keep record of the effects presented by college students before this modality. Natural stress is associated with social isolation through dimensions involving ICTs with the aim of diagnosing the personal, family, social and technological impact on college students in San Luis Potosí, to determine the effects that are adverse to their learning and professional life. The results will contribute to the development of strategies associated with the effective use of the ICTs that institutions offer and facilitate the teaching-learning process; the study also concluded according to the integral well-being of the student in this new modality.

Removal of Heavy Metal Ions from Wastewater Using Hydroxyethyl Methacrylate-Modified Cellulose Nanofibers: Kinetic, Equilibrium and Thermodynamic Analysis

The objective of this work was to fabricate modified cellulose nanofibers (CNFs) for the removal of heavy metal ions (Cd2+ and Pb2+) from wastewater. Cellulose was modified with 2-hydroxyethyl methacrylate (HEMA) via grafting copolymerization using the microwave-assisted technique in the presence of ceric ammonium nitrate (CAN) as an initiator. Prepared cellulose-graft-(2-hydroxyethyl methacrylate) (HEMA/C) copolymers were characterized using Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). Different factors affecting the graft yield, such as irradiation time, monomer concentrations, and initiator concentrations, were investigated. Furthermore, cellulose-graft-(2-hydroxyethyl methacrylate) copolymer nanofibers (HEMA/CNF) were fabricated by electrospinning using N,N-dimethylacetamide-LiCl as a solvent. Electrospun nanofiber copolymers were characterized using SEM and thermogravimetric analysis (TGA). Operating parameters, including time, starting metal concentrations, and adsorbent concentration, were analyzed at a pH of 5.6 for the two metal ions. The best-fit model of adsorption energy was the pseudo-second-order model, and adsorption isotherms at equilibrium were well described by the Langmuir and Freundlich models. The negative values of ΔG and positive values of ΔH and ΔS suggest that the adsorption of Cd2+ and Pb2+ ions onto electrospun HEMA/CNF is a spontaneous, endothermic, and favorable reaction.

The Topological Analysis of the ELFx Localization Function: Quantitative Prediction of Hydrogen Bonds in the Guanine–Cytosine Pair

In this contribution, we recall and test a new methodology designed to identify the favorable reaction pathway between two reactants. Applied to the formation of the DNA guanine (G) –cytosine (C) pair, we successfully predict the best orientation between the base pairs held together by hydrogen bonds and leading to the formation of the typical Watson Crick structure of the GC pair. Beyond the global minimum, some local stationary points of the targeted pair are also clearly identified.

An evaluation of solvent effects and ethanol oxidation

Understanding liquid-metal interfaces in catalysis is important, as the liquid can speed up surface reactions, increase the selectivity of products, and open up new favorable reaction pathways. In this work...

ANTIOKSIDATIVNI KAPACITET ANTRAHINONA IZ BILJKE RUBIA CORDIFOLIA LINN

In this study, the antioxidant and antiradical capacities of anthraquinones from Rubia cordifolia Linn were determined using the DFT method. The thermodynamically most favorable reaction pathways of antioxidant mechanisms were defined, as well as the most favorable antiradical reaction mechanisms for the deactivation of methylperoxyl and methoxy radicals. The calculations were done in the gas phase. HAT is thermodynamically the most favorable mechanism of antioxidant action of the studied anthraquinones, while the most probable mechanism of deactivation of methylperoxyl and methoxy radicals is the SPLET mechanism.

UTICAJ pH VREDNOSTI NA ANTIRADIKALSKI KAPACITET 4,7- DIHIDROKSIKUMARINA

The mechanisms of antiradical activity of 4,7-dihydroxycoumarin against peroxy (HOO•) radical were investigated. For this purpose were used sophisticated computational methods. Investigation was performed in the water, at different pH values (0-14). Acid-base species, which are represented in diverse molar fraction (f) at different pH values, contribute to a comprehensive examination of antiradical capacity. An overall rate constant (koverall) of the favorable reaction pathways (HAT and RAF) of 2.07×102 M-1s-1 at physiological pH indicates a moderate ability to neutralization HOO• radicals. A value of 1.05×103 M-1 s-1 occurring at pH > 10 indicates a maximum antiradical capacity of 4,7-dihydroxymumarin against the HOO• radical.

Equilibrium Studies for Removal of Cadmium (II) Ions Removal from Water Using Activated Carbon Derived from Macadamia Intergrifolia Nutshell Waste Powder

Heavy metals have continued to be of great concern in research as major pollutants of water. Adsorption using low cost adsorbent is a low cost method of the removal heavy metal ions from aqueous solution. In this study activated carbon derived from macadamia intergrifolia nutshell powder was considered as an alternative low cost adsorbent for the removal of Cd(II) ions from aqueous solution. Various physicochemical parameters which included sorbent mass, and initial metal ions concentration isotherms using sorption models were determined. Results from the experiment indicated the optimum values for sorbent mass as 0.3 grams, and initial metal ions concentration as 8mg/l. Adsorption isotherms were found to fit well in Langmuir model (R2=0.9935), Javanovic model (R2 =0.9857) and Freundlich model (R2=0.9911). Additionally, for Langmuir model the value of separation factor (KL) was in the range of 0 to 1 indicating a favorable reaction. For Jovanovic model adsorption energy was found to be 1.00334 l/mg thus an indication of binding vibrations during Cd(II) ions adsorption. FTIR spectrum revealed that the presence of O-H at νmax 3389 cm-1, COO- at νmax 2367 cm-1, C=0 at νmax 1593 cm-1, C-O at νmax 1344 cm-1, P-O at νmax 1206 cm-1 and POO-H at νmax 1110cm-1 functional group in activated carbon enhanced Cd(II) ions removal. The study revealed that activated carbon derived from macadamia intergrifolia nutshell can be used to remove Cd(II) ions from water.