Category Archives: ChemistrySelect

Relevant Advances in the Synthesis and Applications of N‐Glycopyranosides

Posted on 11 October 2023 by

In this work describe the natural occurrence, synthesis, mechanism, and pharmacological applications of N-glycopyranosides.

Abstract

N-glycosides are produced when an aglycone is connected, for example, using a glycosylation reaction, to the sugar moiety via linkage of C−N bond at anomeric carbon. N-glycosides are obtained from different precursors, including glucals, 1-azido glycosides, glycosyl azide, glycosyl isothiocyanate, 2-deoxy-2-iodo-N-glycoside, glycosyl-1H-1,2,3-triazol, and 2-nitroglucal. The biological relevance of N-glycopyranosides has drowned attracted the attention of several researchers. The scope of this review covers the literature from 2010 to 2022. Recent advances focused on the natural occurrence, synthesis, mechanism, and pharmacological applications of N-glycopyranosides are discussed.

Kinetics of Electrocatalytic Oxidation of Gallic Acid by Activated Glassy Carbon Electrode in Acidic Medium

Posted on 11 October 2023 by

Pristine glassy carbon (GC) electrode was just activated by applying voltage +1.8 V vs Ag/AgCl (sat. KCl) reference electrode. Then, using cyclic voltammetry techniques, the prepared activated GC was used to analyse the oxidation of gallic acid in acidic medium, and the resulting data was compared with that of pristine GC.

Abstract

An electrochemically functionalized glassy carbon (GC) electrode was prepared to study Gallic acid (GA) oxidation reaction in an acidic medium. The functionalized GC electrode was found to enhanced GA oxidation reaction in acidic medium by lowering oxidation potential and increasing corresponding current in comparison to a pristine GC. Electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and x-ray photoelectron spectroscopy (XPS) methods were used to analyze functionalized GC surface. The development of electropositive C=O functional groups were assumed to enhance the catalytic process. The specific capacitance of the electrode was calculated to be 92.91 μF by analysing EIS. Kinetics of GA oxidation over activated GC was calculated from CVs data. By analysing concentration dependent CVs it was found that the electrode process followed mass transfer limited first order kinetics. The GA oxidation mechanism is potential-dependent. For potentials above 0.42 V, the oxidation reaction involves the transfer of 2e⁻ and 2H⁺ via a concerted mechanism, while at potentials below 0.42 V, the mechanism is stepwise. The reaction‘s standard rate constant (k°) was evaluated as 2.08×10⁻⁴ cm s⁻¹.

Ultrasound‐assisted efficient aerobic oxidative coupling of thiols to disulfides with DiMIM‐CH3SO4 as a recyclable ionic liquid catalyst in water: A green approach

Posted on 11 October 2023 by

1,3-dimethyl imidazolium methyl sulfate (DiMIM-CH₃SO₄) ionic liquid-catalyzed the aerobic oxidative coupling of thiols to disulfides in water under ultrasonic irradiation at room temperature.

Abstract

An ultrasound-assisted method with specific characteristics of green chemistry for aerobic oxidative coupling of thiols to disulfides is presented. In this method, a readily available ionic liquid catalyzed the aerobic oxidative coupling of thiols to disulfides in water as a green solvent under ultrasonic irradiation at room temperature. In this novel sonocatalysis/ionic liquid protocol, aromatic thiols having both electron-donating and electron-withdrawing substituents, alkyl thiols and cysteine, were cleanly converted to the corresponding disulfides in excellent yields. This methodology uses 1,3-dimethyl imidazolium methyl sulfate (DiMIM-CH₃SO₄) ionic liquid as a recyclable catalyst and aerobic oxygen as an oxidative agent. This protocol has the advantages of high yields, short reaction times, lower cost, environmentally friendly reaction media, easy isolation of products, convenient procedure and recoverability of catalyst.

Recent Progress, Challenges, and Future Prospects in Solar H2 Evolution via Pure/Sea Water Splitting Using Nanocomposites as Photocatalysts under Solar Light

Posted on 11 October 2023 by nPrakash Jakhar, nShaily Sharma, nSurbhi Dhadda, nHimanshu Sharman

This review summarizes a study on photocatalytic solar-driven water splitting, specifically comparing pure and sea water systems for hydrogen (H₂) generation. Sea water shows superior H₂ production under solar light due to cost-effectiveness and ample availability. However, challenges persist in fully harnessing natural light, often necessitating co-catalysts and sacrificial agents to boost efficiency.

Abstract

Photocatalytic pure/sea water splitting driven by solar light, emerges as the most promising strategy to address both the global energy crisis and environmental degradation. Research efforts have mainly resulted in the development of artificial photocatalytic solar hydrogen generation systems applicable to both freshwater and sea water. During long-term testing, sea water demonstrated enhanced stability compared to pure water, offering experimental advantages in designing novel techniques aimed at reducing hydrogen generation costs, alleviating freshwater scarcity, and optimizing the utilization of natural water resources. Moreover, sea water splitting proves to be more effective in producing solar hydrogen due to the potential sacrificial action of salt ions, which promote hydrogen evolution within the photocatalytic system. This review comprehensively outlines the fundamental principles of photocatalytic H₂ production, examines the efficiencies and recent progress in hydrogen generation, explores the challenges faced, and envisions the future prospects of enhancing hydrogen production efficiency and reactivity through photocatalytic pure/sea water splitting.

TBA−Br and Selectfluor Mediated Bromination of Glycals and Heterocyclic Compounds: Substrate Scope and Synthetic Utility

Posted on 11 October 2023 by nMittali Maheshwari, nNazar Hussainn

The metal-free stereoselective procedure is developed by using selectfluor and TBAB as a reagent system for the dibromination of sugar enol-ethers and monobromination of heterocyclic compounds. This protocol attained dibrominated product with glycals in 5 minutes at room temperature with excellent yields. For substituted indoles and chromones, same reagent system delivered the 3-brominated products but at elevated temperatures. Further, the synthetic utility was shown by synthesizing 3-aryl indoles and isoflavones via Suzuki-Miyura cross-coupling reactions.

Abstract

Herein, we have devised a metal-free stereoselective protocol mediated by selectfluor for the dibromination of sugar enol-ethers and monobromination of heterocyclic compounds. The dibromination of glycals was achieved within 5 minutes at room temperature with excellent yields. The tolerance of various protecting groups such as acetyl, benzyl, and silyl in sugars was checked. When the same reagent system was applied to substituted indoles and chromones 3-brominated products were obtained but at elevated temperatures. The synthetic utility of the methodology was demonstrated by using the brominated indoles and chromones to synthesize the 3-aryl indoles and isoflavones respectively via Suzuki-Miyura cross-coupling reactions.

Iron ions embedded in hexagonal mesoporous silica via a simple method: implementation in mild oxidation catalysis

Posted on 11 October 2023 by

Mesoporous silica monoliths containing dispersed Fe^III sites have been prepared using a simple and cheap synthetic procedure. These materials are efficient as epoxidation catalysts by hydrogen peroxide under mild conditions. The textural and spectroscopic analyses of these materials reveal that the catalytic activity results from a compromise between several parameters such as the pore diameter and the hydophobicity of the silica walls.

Abstract

Mesoporous silica monoliths containing dispersed Fe^III sites have been prepared following a direct and simple synthetic method. The iron-containing materials are able to catalyze the epoxidation of cyclooctene by H₂O₂ under mild conditions. Textural and spectrophotometric analyses reveal that, when the thermal treatment temperature of the materials increases (from 500 °C to 1000 °C), the pore diameter of the silica matrix decreases while the formation of small oxo-iron(III) clusters is promoted. Among the five materials obtained after treatment at 500, 700, 800, 900 or 1000 °C, the one prepared at 700 °C exhibits the best catalytic performances. This indicates that a compromise must be found between several parameters, such as the pore size (which decreases with calcination temperature) and the hydrophobicity of the channel surface (which is favored at higher temperature), for an optimal reactivity.

A Facile and Fast Syntheeis of Barium Molybdate Nanoparticles: Effects of PH and Surfactant

Posted on 11 October 2023 by nAdem Sarılmazn

BaMoO₄s with nano-sized and homogeneous particle distribution were obtained at low reaction temperatures and time. Also, the effects of pH values and surfactant types on the morphologies of particles were investigated. In addition, the properties of BaMoO₄ particles obtained by the co-precipitate method were characterized using various analysis methods.

Abstract

Barium molybdate (BaMoO₄) is one of the materials used extensively in electronic and optical devices. Although there are many synthesis methods in the literature, a route for facile synthesis of nano-BaMoO₄ has been ignored. In this study, BaMoO₄ nanoparticles were produced by the co-precipitation method at room temperature within a short time. The effects of ammonia solutions and surfactants on the morphology of the particles were investigated. Various properties of these materials were characterized by XRD, SEM-EDX, elemental mapping, TEM, and UV-Vis analysis methods. Also, the crystal structure parameters and the compatibility of these values with the theoretical calculations were determined by Rietveld refinement. From the HR-TEM image, the interplanar spacing was calculated as 3.2 Å. It was determined from these analyses that BaMoO₄ particles with optical band gaps varying between 3.80 and 3.95 eV were produced in nano and micrometer sizes. It has been demonstrated by this study that the pH of the synthesis solution and the type of surfactant have significant effects on the morphological and optical properties of the materials.

The Effect of Different Morphologies of Polyaniline on Its Catalytic Activity for the Thermal Decomposition of Ammonium Perchlorate

Posted on 11 October 2023 by

NP-PANi was synthesized by three different methods comprising: chemical, sonochemical, and electrochemical routes. The synthesized polymers were deeply characterized using FTIR, N₂ adsorption-desorption, FESEM, and EDAX analysis. From BET results, electro-PANi has the highest surface area, highest pore volume, and the smallest pore size among others and, as expected revealed the best catalytic activity. It merged two peaks of AP decomposition into a drastically solo sharp peak revealed at low temperature (approximately 90 °C lower than) and increased the enthalpy of the reaction significantly by about 140 %.

Abstract

In this study, a novel strong green catalyst as a promising replacement for conventional transition metal oxides (TMOs) based burning rate modifiers was introduced. For this aim, the morphology of the nano-porous polyaniline (NP-PANi) was manipulated by changing its synthesis method, and the effect of that on the activity of the catalyst on the thermal decomposition of ammonium perchlorate (AP) was investigated. To achieve this goal, NP-PANi was synthesized by three different methods comprising: chemical, sonochemical, and electrochemical routes. The synthesized polymers were deeply characterized using FTIR, N₂ adsorption-desorption, FESEM, and EDAX analysis. From BET results, electro-PANi has the highest surface area, highest pore volume, and the smallest pore size among others and, as expected revealed the best catalytic activity. It merged two peaks of AP decomposition into a drastically solo sharp peak revealed at low temperature (approximately 90 °C lower than) and increased the enthalpy of the reaction significantly by about 140 %. The obtained results can open a new window in the world of practical green burning rate modifiers for the energetic material industry.

Preparation of an Activated Carbon Composite with High Thermal Conductivity Based on Emulsified Asphalt and Carbon Nanotubes and its Adsorption Performance for n‐Hexane

Posted on 11 October 2023 by

The preparation process of composite activated carbon is mainly from stirring, then high temperature sintering to carbon, followed by a large amount of water washing to remove impurities, and finally drying to obtain composite activated carbon. During the high temperature sintering, asphalt is carbonized to form fluffy carbon material, which increases a lot of space for the loading of CNTs.

Abstract

Activated carbon, as the main adsorption material for treating VOCs, has been widely used. To solve the problem of safety hazards in activated carbon adsorption process due to the large amount of heat released, highly thermally conductive composite activated carbon (A-AC/CNTs) was prepared using asphalt and highly thermally conductive carbon nanotubes (CNTs) for thermal conductivity improvement. Uniform dispersion and firm loading of CNTs in the carbon production material were achieved by dispersing carbon nanotubes (CNTs) in the asphalt-in-water emulsion. Experimental results showed that the specific surface area of A-AC/CNTs reached a maximum when the loading of CNTs was 0.5 wt %. Meanwhile, the thermal conductivity increased by 1.5 times compared with the original activated carbon. The adsorption capacity of n-hexane reached the maximum of 2868 mmol ⋅ g⁻¹, and the adsorption capacity increased by 21.41 %. It also maintained good regeneration performance after dynamic adsorption experiments.

Facile Synthesis of Citric Acid Functionalized Fe3O4@Activated Carbon Magnetic Nanocomposite for Efficient Adsorption of Brilliant Green Dye from Wastewater

Posted on 11 October 2023 by

Surface of Citric acid functionalized Fe₃O₄/Activated Carbon behaves as cationic and anionic depending on its point zero charge (pH~8), which lead to various adsorbent-dye interactions. Brilliant green dye shows superior adsorption behaviour near neutral condition as depicted from the plot of dye removal percentage as a function of contact time owing to the surface interactions such as electrostatic interactions and hydrogen bonding.

Abstract

Owing to the impact of brilliant green dye on potable water contamination, citric acid functionalized magnetic nanocomposite in presence of activated carbon was prepared for easy, quick, and efficient removal of the dye from water. Batch adsorption studies were conducted to maximize the adsorption efficiency by optimizing contact time, initial dye concentration, pH, dosage, and salt concentration. The maximum efficiency of the citric acid functionalized Fe₃O₄@activated carbon was found to be 773 mg g⁻¹. The efficiency of the monolayer adsorption process as depicted from the Langmuir model is explained based on the hydrogen bonding, electrostatic interaction, and porosity of the adsorbent. The adsorption process follows a pseudo-second order kinetics model which can also be correlated to the relatively quick adsorption process. The saturation magnetization of the nanocomposites prepared in presence of activated carbon was found to be 35.2 emu/g, which makes it effective for quick magnetic separation. Built on the findings, we report an economical, efficient, and satisfactory alternative adsorbent for the abatement of brilliant green dye from coloured wastewater and contaminated water sources.