Chemical Research Research Articles

Exploring the Mechanisms and Kinetic Modeling of Phenol Amination Using Pd and Rh‐Based Catalysts

AbstractProducing biomass‐derived chemicals to substitute their petrochemical counterparts has long been an aspiration of the green chemistry research community. However, synthesizing secondary amines from biomass precursors presents several challenges related to catalyst nature and the mechanistic understanding of reaction systems. Here, we unravel the mechanistic and kinetic implications of the reductive amination of phenol with cyclohexylamine over Pd/C and Rh/C. A competitive Langmuir‐Hinshelwood reaction model well interpreted the kinetic data, suggesting that support‐metal interfaces serve as active sites for H2, ─NH2 and ═NH activation. The apparent activation energies for imine hydrogenation were 87.6 kJ mol−1 (Pd/C) and 34.5 kJ mol−1 (Rh/C), while ΔHads and ΔSads values confirmed the physicochemical consistency of the model. Moreover, the catalysts demonstrated their high stability to operate for several catalytic cycles, with minor activity losses due to metal leaching and partial sintering of Pd nanoparticles. Despite phenol reductive amination following similar mechanisms on Rh/C and Pd/C, they show differences in selectivity because the hydrogenation of imine is more efficient on Rh0 than on Pd0. This is the first mechanism‐oriented kinetic study for phenol reductive amination; thus, it provides valuable information for process design and scale‐up.

Palladium(II) and platinum(II) thiophene-based thiosemicarbazones: Synthesis, properties, and anticancer studies

The aim of this study was to synthesize and investigate the cytotoxic profile of four palladium(II) and two platinum(II) complexes containing thiosemicarbazones derived from thiophene against tumor cells. They were fully characterized by various analytical techniques, including 1H, 13C{1H}, 31P{1H}, 135DEPT NMR, IR, UV–vis, X-ray diffraction, molar conductivity, and theoretical. Several techniques were used to evaluate the interaction of the complexes with DNA, such as gel electrophoresis, UV–vis spectroscopy, circular dichroism, viscosity measurements, fluorescence assay with Hoescht 33,258, and molecular docking. The results indicated that the complexes exhibited electrostatic and/or groove interaction with DNA, but only at high concentrations (100 µM). In vitro, cytotoxicity assays were performed using the MTT method, and the palladium(II) complexes showed remarkable cytotoxic activity against A549 and A2780cis cell lines. In particular, the PdT compound showed cytostatic behavior against the A549 tumor line, while the PdCH3 compound showed cytotoxic behavior against the A2780cis line. Further investigation of the most promising compound, PdCH3, in A2780cis revealed that it induced apoptosis by promoting cell accumulation in the sub-G1 phase and causing partial mitochondrial membrane depolarization. In addition, this complex significantly inhibited colony formation, leading to significant changes in cell morphology. However, no inhibition of cell migration was observed in the 3D cell model of DAOY cells. These findings provide valuable insights and structural features for the design of selective palladium complexes targeting ovarian tumor cells (A2780cis). The study highlights the potential of these complexes as cytotoxic agents against specific cancer cell lines, paving the way for future advances in medicinal chemistry research.

Trends in Research on Representation in Chemistry Learning: A Systematic Review

Representation plays an important role in helping students understand chemistry learning. This is due to the many chemical concepts that require visualization. Representation is something that still needs to be studied. So this study aims to see the development of representation research in chemistry education. The articles used in this study are articles from 2018 to 2022. This Systematic Literature Review research used Publish or Perish software, then filtered and extracted data according to the criteria for the research objectives to create 30 relevant articles and combined using the Prisma Protocol. The results showed that research related to representation in chemistry learning is still frequently conducted in the last 5 years. This research often discusses related to cognitive ability, which is most associated with chemistry concepts and conceptual understanding. Students and teachers are commonly used samples in research. In addition, stated of matter is most widely used subject in chemistry research.

Tyramine-assisted fluorescent labeling of polysaccharides: Characterization, and interfacial properties

Fluorescence labeling has been widely used in various fields, including fluorescent sensors, biochemistry, medical and chemical research. This study proposed an efficient strategy for the detection and microanalysis of polysaccharides. Soy hull polysaccharide (SHP) was successfully labeled with fluorescein isothiocyanate (FITC) via an amination reaction using tyramine as a linker. The labeled polysaccharide (FTSHP) was characterized by fluorescence, UV–visible, flourier transform infrared (FT-IR), 1H NMR, differential scanning calorimetry (DSC) and interfacial tension. The results indicated that the labeling efficiency of FTSHP with different concentration of FITC (0.20–0.35 wt%) was 1.51 %, 1.58 %, 1.63 %, and 1.67 %, respectively, with fluorescence intensity increasing as FITC concentration increased. Moreover, the interfacial adsorption capacity and thermal stability of FTSHP were significantly improved compared to SHP. This labeling method offers a promising approach for detection and analysis of polysaccharides, providing new insights into the study of other natural polysaccharides.

Air-stable, well-defined palladium–BIAN–NHC chloro dimer: Highly efficient N-Heterocyclic carbene (NHC) catalyst platform for Buchwald–Hartwig C–N cross-coupling reactions

Buchwald-Hartwig amination has become the fundamental method for constructing molecular architectures throughout chemical research, including the synthesis of pharmaceutical agents, natural products, fine chemicals, and advanced materials. Herein, we report air-stable, well-defined palladium–BIAN–NHC chloro dimer, [Pd(BIAN–NHC)(μ-Cl)Cl]2, for Buchwald-Hartwig C–N cross-coupling reactions of aryl halides. This rapidly activating catalyst framework merges the reactive properties of palladium chloro dimers, [Pd(NHC)(μ-Cl)Cl]2, with the structural features of acenaphthoimidazol-2-ylidenes. [Pd(BIAN–NHC)(μ-Cl)Cl]2 is the most reactive Pd(II)–NHC precatalyst to date, undergoing fast activation under both inert atmosphere and aerobic conditions. The catalyst shows an excellent reactivity in Buchwald-Hartwig amination of aryl halides (59 examples), including challenging substrates, diamination and direct functionalization of pharmaceuticals. The steric protection enables high reactivity under both inert atmosphere and aerobic conditions. [Pd(BIAN–IPr)(μ-Cl)Cl]2 should be routinely utilized for the synthesis of C–N bonds to make valuable amines, where it replaces the most commonly deployed at present IPr (IPr = 1,3-bis(2,6-isopropyl)imidazol-2-ylidene).

Holistic exploration of silver nanoparticles synthesized from Carthamus oxycantha leaf extracts: Characterization and assessment of antioxidant, anti-α-amylase, and anti-cholinesterase activities using comprehensive statistical methods

In the burgeoning field of nanotechnology, plant-mediated nanoparticles (NPs) have attracted significant attention due to their small size, favorable chemical properties, and eco-friendly nature. We utilized Carthamus oxycantha leaf extract to synthesize silver nanoparticles (AgNPs) and evaluate their potential as antioxidants and inhibitors of acetylcholinesterase (AChE) and alpha-amylase (α-amylase). The AgNPs were characterized using advanced techniques. The UV–Vis spectrum recorded at 410 nm, with an absorbance of 2.3 a.u., confirmed the presence of AgNPs. Fourier transform infrared spectroscopy (FT-IR) indicated that functional groups from the extract were attached to the AgNP surface, aiding in their formation and stabilization. X-ray diffraction analysis (XRD) revealed four major peaks at 37, 43, 64, and 77, confirming AgNP synthesis. Scanning electron microscopy (SEM) showed that 80 % of the AgNPs were spherical, measuring 25–50 nm, while energy dispersive X-ray (EDX) analysis indicated that silver constituted 83 % of the material. The AgNPs demonstrated significant scavenging activity: 59.3 % with ABTS, 67.2 % with ammonium molybdate, 60.35 % with DPPH, 65.2 % with ferric chloride, and 55.2 % with H2O2. Both α-amylase and AChE were inhibited by AgNPs, exhibiting uncompetitive inhibition characteristics. For glucophage, Km decreased from 143 to 75 µg, and Vmax decreased from 45 % to 72 % as concentrations increased from 50 to 150 µg. The Km of AgNPs decreased from 25 to 17 µg, and Vmax decreased from 16 % to 37 %. The extract showed noncompetitive inhibition against α-amylase, while AgNPs caused noncompetitive inhibition in AChE. These findings highlight the potential of AgNPs as therapeutic agents for managing oxidative stress and enzyme-related disorders, paving the way for future research and applications in medicinal chemistry.

Nanocellulose and microcrystalline cellulose from citrus processing waste: A review.

Used since decades to produce pectin, citrus processing waste poor in lignin and rich in hemicellulose obtained from lemon and orange juice industrial manufacturing is ideally suited also as microcrystalline cellulose and nanocellulose raw material. The study merges the outcomes of chemistry and bioeconomy research between 2007 and early 2024 with technology and economic insight, to reach five conclusions that will hopefully inform practice-oriented work of researchers and bioeconomy company's managers interested in the sustainable manufacturing of these important biomaterials.

Green chemistry in manufacturing: Innovations in reducing environmental impact

Green chemistry has emerged as a transformative approach in reducing the environmental impact of the manufacturing industry. This review paper provides a comprehensive examination of how green chemistry principles are applied in various manufacturing sectors to minimize hazardous waste and energy consumption. The paper begins by outlining the core principles of green chemistry, highlighting their relevance to sustainable industrial practices. Key innovations in chemical engineering are discussed, focusing on waste reduction, energy-efficient processes, and the use of renewable raw materials. Through detailed case studies in the pharmaceutical, textile, and automotive industries, the paper demonstrates how the adoption of green chemistry has significantly reduced the environmental footprint of these sectors. The review also explores the challenges industries face in implementing green chemistry and the future direction of this field, emphasizing the role of policy and regulatory frameworks in driving further innovation. The findings suggest that while progress has been made, there are substantial opportunities for growth, especially in expanding the use of green chemistry across diverse industries. This paper concludes with recommendations for continued research and broader adoption of green chemistry to promote sustainable manufacturing.

Measuring the purity of organic chemicals: general approaches and development of an appropriate procedure for research of pure organic chemicals

Pure materials are in demand in many sectors of the national economy, including the metrological service. High purity organic material is the ultimate source of metrological traceability in organic analysis to the basic units of the International System of Units (SI). This article presents the general approaches to determining the mass fraction of the main component in pure organic chemicals, which provide a traceable connection between the certified value of substance purity and the basic SI units - mass (kilogram) and amount of substance (mole), the features of using direct and indirect measurement approaches are considered, specific analytical methods that can be used for this purpose are discussed. Determining the purity of an organic material in most cases is not a plain analytical and metrological task. Solving this issue requires the relevant instrumental methods and appropriate measurement procedure, which is able to provide a comprehensive study of organic matter and guarantee the necessary accuracy of the certified value. Taking in consideration the vast diversity of organic chemicals, the determination of the purity of organic substances will never be a standardized procedure.

Reflections in Chemical Safety and Research: Making Technical Research Relevant for Students and Bangladesh

Reflections in Chemical Safety and Research: Making Technical Research Relevant for Students and Bangladesh

Upcycling sugar beet waste into sustainable organo-nanocatalysis for carbon dioxide fixation and cyclic carbonate synthesis: a research design study

Environmental pollution is a major global issue due to the increase of various pollutants all over the world. Enhancing pollutant remediation strategies for environmental sustainability necessitates increasing the efficiency of conventional methods or introducing innovative approaches. Nanotechnology, particularly carbon-based nanomaterials, offers substantial promise due to their high surface area and absorption potential. Concurrently, organocatalysts have emerged as sustainable and versatile alternatives to traditional metal-based catalysts in modern chemical research. This study highlights the synthesis and application of organo-nanocatalysts derived from biomass, specifically a spherical carbon nanocatalyst synthesized from sugar beet pulp. This novel green catalyst, characterized by high selectivity and efficiency, successfully converts epoxides and CO2 into valuable cyclic carbonates under solvent-free conditions. The hydroxyl groups on the Sugar Beet-derived Carbon NanoSphere (SCNS) surface act as Bronsted acid sites, facilitating epoxide activation via hydrogen bonding. The integration of carbon-based nanomaterials and organocatalysis represents a promising, sustainable solution for pollutant remediation and green chemistry advancements.Graphical

Infrared Spectra Prediction for Functional Group Region Utilizing a Machine Learning Approach with Structural Neighboring Mechanism.

Infrared (IR) spectroscopy is a pivotal technique in chemical research for elucidating molecular structures and dynamics through vibrational and rotational transitions. However, the intricate molecular fingerprints characterized by unique vibrational and rotational patterns present substantial analytical challenges. Here, we present a machine learning approach employing a structural neighboring mechanism tailored to enhance the prediction and interpretation of infrared spectra. Our model distinguishes itself by honing in on chemical information proximal to functional groups, thereby significantly bolstering the accuracy, robustness, and interpretability of spectral predictions. This method not only demystifies the correlations between infrared spectral features and molecular structures but also offers a scalable and efficient paradigm for dissecting complex molecular interactions.

Photocatalytic Decarboxylative Allylation of α-Amino Acids and Peptides under Metal-Free Conditions.

We developed an organophotoredox catalytic system to facilitate the decarboxylative allylation coupling process concerning α-amino acids and related C-terminal carboxylate peptides using Morita-Baylis-Hillman adducts as allylic precursors. This metal-free method operates under mild conditions and is compatible with various amino acids. The versatility of this protocol, particularly in chemical biology research, has been preliminarily demonstrated through the ligation of bioactive peptide chains.

Spectroscopic study of wemple-didomenico empirical formula and taucs model to determine the optical band gap of dye-doped polymer based on chitosan: Common poppy dye as a novel approach to reduce the optical band gap of biopolymer

This study investigates the effect of a natural dye extracted from common poppy (Papaver rhoeas) waste flowers on the optical properties of chitosan (CS) films. The extraction of natural dyes from waste flowers can be considered a new field for research in green chemistry. CS films are flexible and biodegradable but have low optical activity and band gap, limiting their applications in optical devices. The doped CS polymer with different concentrations of Papaver rhoeas dye exhibited enhanced optical properties. Also, 30 % glycerol was added as a plasticizer to omit film brittleness. The FTIR examinations is helpful to propose a mechanism that explains the interaction of the dye with the host polymer. The UV–vis spectroscopic examination establish that the optical characteristics of the films can be modified by adjusting the dye concentration. Furthermore, optical absorption properties are described using the Tauc non-direct transition model, revealing an approximate optical band gap of 1.64 eV. This band gap defines the energy required for electron transitions, elucidating the material’s electronic characteristics. The extinction coefficient (k) and refractive index (n) of the CS-doped films’ shows a dispersion behavior at visible regions of EM radiation. The Wemple-DiDomenico single oscillator model was used to investigate the n dispersion and determine the oscillator energy equivalent to the optical band gap. Additionally, calculations have been performed on optical dielectric properties and optical conductivity. The Urbach energy was measured and used to detect the structure of the films. The findings underscore the potential applications of these natural dye-doped CS films in eco-friendly materials and optical devices.

Advancing Lung Cancer Diagnosis through NH2-MON-SPME-GC-MS/MS: Enhanced Sensitivity in Aldehyde Biomarker Detection from Exhaled Breath.

The sensitive detection of trace biomarkers in exhaled breath for lung cancer diagnosis represents a critical area of research in life analytical chemistry, with profound implications for early disease detection, therapeutic intervention, and prognosis monitoring. Despite its potential, the analytical process faces significant challenges due to the ultratrace levels of disease biomarkers present and the complex, high-humidity composition of exhaled breath. This study introduces a highly sensitive method for detecting aldehyde biomarkers in exhaled breath by integrating the use of amino-functionalized microporous organic networks (NH2-MON) as a solid-phase microextraction (SPME) fiber coating with gas chromatography-triple quadrupole mass spectrometry (GC-MS/MS) analysis. The method innovatively combines sample collection and extraction, achieving a dual-step enrichment process that significantly enhances both the enrichment efficiency and reproducibility of biomarker detection while effectively mitigating the interference caused by water vapor in exhaled breath. The NH2-MON, utilized as an SPME fiber coating, demonstrates exceptional enrichment capacity for five key aldehyde biomarkers, facilitating the development of a highly sensitive detection approach for these biomarkers in exhaled breath. Compared to previously reported methods, the proposed technique exhibits significantly lower limits of quantification, ranging from 0.77 to 11.89 pg mL-1, and achieves substantially higher enrichment factors, ranging from 9156- to 35723-fold. The practicality and feasibility of the method were validated through the analysis of exhaled breath samples from lung cancer patients, underscoring its potential application in the early diagnosis and monitoring of lung cancer.

Construction of Aryl Azide‐ and Triazole‐Based Unnatural Amino Acid Motifs via the Pd(II)‐Catalyzed C(sp3)‐H Arylation

This paper reports a method for the synthesis of examples of aryl azide‐ and triazole moiety‐based unnatural amino acid motifs using the Pd(II)‐catalyzed arylation of the prochiral C(sp3)‐H bonds of carboxamides of amino acids as one of the key transformations. Synthesis of racemic and enantioenriched aryl azide‐based unnatural amino acid motifs including, norvaline, leucine, norleucine, phenylalanine, 2‐aminobutyric acid, 2‐aminooctanoic acid, and non‐α‐amino acid derivatives were shown. Additionally, we attempted the synthesis of triazole moiety‐installed norvaline, leucine, norleucine, phenylalanine, 2‐aminobutyric acid, 2‐aminooctanoic acid, and non‐α‐amino acid derivatives via the Cu‐catalyzed Click reaction. We also demonstrated the removal of the protecting groups and the synthesis of free amino group‐containing aryl azide‐ or triazole‐based unnatural amino acid motifs and peptides. Generally, azide moiety‐containing unnatural amino acid motifs are important molecular tools in chemical biology. Furthermore, aryl azide‐ and triazole moiety‐containing unnatural amino acid scaffolds are notable substrates in medicinal chemistry and drug discovery research. Accordingly, this work contributes to enriching the library of aryl azide‐ and triazole‐based unnatural amino acid derivatives.

Application of C-H Functionalization in the Construction of Pyrene-Azobenzene Dyads

This paper reports the synthesis of pyrene-azobenzene dyads using the Pd(II)-catalyzed directing group-assisted arylation of ortho C(sp2)-H bond of pyrene carboxamide as one of the key transformations. We have shown the synthesis of many examples of directly connected pyrene-azobenzene dyads (without any linker) and glycine-based azobenzene-pyrene dyads. At first, an acetanilide unit was incorporated in the pyrene skeleton through Pd(II)-catalyzed directing group-assisted ortho C(sp2)-H arylation by using iodoacetanilide. Then, the acetanilide moiety in the pyrene skeleton was transformed into an azobenzene unit to give the pyrene-azobenzene dyad. The UV-Vis spectroscopic studies have been performed to get the absorption properties (λmax (nm)) of all the compounds. Preliminary photoswitching studies in both forward and reverse directions and their related thermal reverse Z-E isomerization kinetics measurements were ascertained for representative compounds. Considering the importance of pyrene and azobenzene linked motifs as important chromophore-based photoswitchable molecules in chemical, materials, and supramolecular sciences research fields, this work enriches the library of pyrene-azobenzene dyads.

A High-Performance Microwave Heating Device Based on a Coaxial Structure

Continuous-flow microwave heating stands out for its ability to rapidly and uniformly heat substances, making it widely applicable in chemical production. However, in practical applications, the permittivity of the heated liquid changes dramatically as the reaction progresses, affecting the efficiency and uniformity of continuous-flow heating. Herein, this work presents a novel microwave heating device based on a coaxial structure for high-performance heating. Our approach commenced with the development of a multiphysical field model, incorporating spiraled polytetrafluoroethylene (PTFE) as a water channel and the coaxial waveguide as a container. The analysis shows that the uniform distribution of the sectional electric field of electromagnetic waves in the TEM mode within the coaxial structure can enhance heating uniformity. Then, a continuous-flow microwave heating system for different liquid loads was established, and experimental measurements were conducted. The heating efficiency for all loads exceeded 90%, which basely matched the simulation results, validating the accuracy of the model. Finally, the heating efficiency and uniformity under different permittivity loads were analyzed, as well as the impact of channel radius on heating efficiency. The device exhibits high heating efficiency under different loads, with uniform radial electric field distribution and stable heating uniformity. This continuous-flow microwave device is suitable for chemical research and production because of its high adaptability to the large dynamic range of permittivity, contributing to the promotion of microwave energy applications in the chemical industry.

Urinary Thioproline and Thioprolinyl Glycine as Specific Biomarkers of Formaldehyde Exposure in Humans.

Assessment of personal formaldehyde (FA) exposure is most commonly carried out using formate as a biomarker, as it is the major product from FA metabolism. However, formate could also have originated from the metabolism of other endogenous and exogenous substances or from dietary intake, which may give rise to overestimated results with regard to FA exposure. We have developed and validated a liquid chromatography-tandem mass spectrometry (LC-MS/MS) coupled with an isotope-dilution method for rigorous quantitation of two major urinary FA conjugation products: thioproline (SPro) and thioprolinyl glycine (SPro-Gly), formed in the reaction between FA and endogenous cysteine or cysteinyl glycine, respectively, as marker molecules to assess personal FA exposure. Using this newly developed method, we measured the FA exposure levels in cigarette smokers, occupants of a chemistry research laboratory and typical domestic household, and visitors to a Chinese temple with a Pearson correlation coefficient greater than 0.94, showing a strong linear correlation between urinary adduct levels and the airborne FA level. It is believed that quantitation of urinary SPro and SPro-Gly may represent a noninvasive, interference-free method for assessing personal FA exposure.

The emergence of electron spin in interdisciplinary research in chemistry.

The emergence of electron spin in interdisciplinary research in chemistry.