Search Results (87)

The instability of marine low-sulfur fuel oil caused by asphaltene precipitation poses significant operational challenges in the shipping industry. This study systematically investigates the dispersing effects of biodiesel derived from three different feedstocks—palm oil, waste cooking oil (WCO), and microalgae oil—and their individual fatty acid methyl ester components on asphaltenes extracted from VLSFO. Biodiesel was selected as a dispersant due to its renewable nature, polar ester functional groups, and variable unsaturation levels, which enable favorable interactions with asphaltene molecules through hydrogen bonding and π-π stacking. Using UV–Visible spectrophotometry, the dispersion performance was quantitatively evaluated under various conditions including dispersant concentration, temperature, storage time, and molecular structural characteristics. The results demonstrate that microalgae oil biodiesel exhibits the most superior asphaltene dispersion capability among the three biodiesels, with a dispersion improvement index of 35% at 12 g/L, compared to 28% and 22% for waste cooking and palm oil biodiesels. Optimal performance is achieved at 80 °C, where the asphaltene concentration increases by 68% relative to the control, and remains stable within the first 10 days of storage but deteriorates significantly after 30 days due to oxidative degradation. Among individual FAME components, the dispersion effectiveness increases with alkyl chain length from C10 to C20, with the latter reaching a 30% improvement index. Functional group polarity plays a critical role, with carboxylic acid exhibiting a 45% improvement at 14 g/L, substantially outperforming alcohol at 32% and ester at 28%. The degree of unsaturation further enhances dispersion, as the improvement index rises progressively from 20% for saturated methyl stearate to 42% for tri-unsaturated methyl linolenate, representing a 2.1-fold increase. Dynamic light scattering (DLS) measurements confirm that biodiesel addition reduces asphaltene particle size from the micrometer range of 2 to 5 μm down to submicron levels of 200 to 500 nm, while microscopic observations reveal inhibited aggregation. These findings provide theoretical foundations for biodiesel application in marine fuel systems. Full article

Lignin, a complex and heterogeneous polymer, poses significant challenges for effective thermal valorization due to its broad molecular weight distribution and structural diversity. This study systematically compares the effect of lignin’s molecular weight on product distribution under pyrolysis and Ru/C-catalyzed depolymerization conditions. Fractionated lignin samples with distinct molecular weights were subjected to identical thermal and catalytic conversion pathways. Pyrolysis results indicate that, compared with low-molecular-weight (low-MW) lignin, high-molecular-weight (high-MW) lignin more readily generates phenolic compounds, with the relative content of guaiacol increasing by nearly twofold. In contrast, products derived from low-MW lignin contain a higher abundance of unsaturated structures, such as 4-allyl-2,6-dimethoxyphenol, suggesting that side chain cleavage and rearrangement reactions are more pronounced. In contrast, Ru/C-catalyzed depolymerization exhibits a stronger molecular-weight-dependent selectivity, where low-MW lignin is more readily converted into carboxylic acids due to enhanced accessibility of terminal functional groups and reduced structural condensation. This comparative analysis demonstrates that lignin’s molecular weight plays a process-dependent role in governing product distribution, providing guidance for tailored lignin valorization strategies. Full article

Ferrocenium catalysis is a growing field of research. This study investigates the catalytic activity of different ferrocenium salts in propargylic substitution reactions to afford propargylic ethers. Four different ferrocenium catalysts were employed in the title reaction, which was monitored over time. The rate of the disappearance of the starting material can be fitted to a first order rate law and observed rate constants were determined. The catalyzed propargylic substitution reactions display a moderate but discernible dependence on the ferrocenium counterion. The lack of an induction period for the reaction indicates that the ferrocenium cation itself is catalytically active, and not just a decomposition product thereof, which would result in an induction period. The presence of a carboxylic acid substituent on one of the cyclopentadienyl rings enhances catalytic activity. The Meyer–Schuster rearrangement of the propargylic alcohol to the corresponding conjugated enone played only a minor role in the ferrocenium-catalyzed reactions. Catalyst decomposition moderately retards the reaction but does not suppress product formation, as demonstrated by experiments with aged FcBF₄. In contrast, the presence of TEMPO as a radical scavenger completely inhibits product formation, while not causing detectable catalyst decomposition at room temperature. In turn, FeCl₃ catalyzes both the propargylic substitution and the Meyer–Schuster rearrangement equally and decomposes the catalysis product over time. These findings reinforce the notion that strong Lewis acids readily promote the rearrangement of propargylic alcohols and that Lewis acidity plays a crucial role in finding a balance between the substitution reactions of propargylic alcohols and their rearrangement to unsaturated aldehydes. Full article

2-Oxazolines are five-membered heterocyclic compounds with significant biological properties. They also play an important role in organic synthesis, acting as chiral ligands and protecting groups for hydroxyamino acids and amino alcohols. Poly(2-oxazolines) are known coating materials, for example, in biomedicine. Classic synthetic methods of 2-oxazolines involve a dehydrative cyclisation reaction between amino alcohols and carboxylic acids, acid chlorides, nitriles, imidates, and aldehydes. However, the electrophilic intramolecular cyclization of unsaturated amides is becoming an increasingly important synthetic method for the preparation of 2-oxazolines. This brief review summarizes procedures for synthesizing oxazolines using the electrophilic intramolecular oxidative cyclisation of N-allyl and N-propargyl amides, as published between 2014 and 2024. It covers the synthesis of 5-halomethyl-, 5-trifluoromethyl-, 5-sulfonylmethyl-, 5-sulfenylmethyl-, 5-selenylmethyl-, 5-acetoxymethyl-, 5-hydroxymethyl-, 5-aminomethyl-, 5-alkilo-, and 5-alkylideneoxazolines. Full article

A series of novel γ-halo-δ-lactones and δ-halo-γ-lactones bearing a phenolic ring at the β-position were synthesized from vanillin. The divergent seven-step synthetic route commenced with the benzyl protection of the hydroxy group of the starting material, followed by a four-step transformation that led to the corresponding β-aryl-γ,δ-unsaturated carboxylic acids. Subsequent halolactonization (iodo-, bromo-, and chlorolactonization), followed by selective benzyl deprotection, gave the target halolactones. The structures of all intermediates and final lactones were confirmed by comprehensive spectroscopic analyses, including NMR and HRMS. The resulting halolactones were evaluated for antiproliferative activity against two canine (CLBL-1, CLB70) and two human (T-24, CaCo-2) cancer cell lines, as well as non-cancerous mouse embryonic fibroblasts (NIH/3T3). Hemolytic assays were performed to assess toxicity against human red blood cells (RBCs). Among the tested lactones, the transδ-iodo-γ-lactone was the most active, particularly against CLBL-1 and T-24 cells. All compounds demonstrated no inhibitory effects on normal fibroblasts and no hemolytic toxicity. This favorable selectivity profile positions this group of lactones, particularly trans-δ-iodo-γ-lactone, as a promising candidate for further development as potential anticancer agents. Full article

Strategic scaffolds in molecules increase the possibility of obtaining derivatives with potential uses in scientific and industrial areas. The regio- and stereoselective reactions can be considered to gain these tactical motifs. Natural diterpenes are key molecules for reaching such aims. Among this class of compounds, neo-clerodanes are highlighted by the presence of a furan moiety in their chemical structure. This work describes a regio- and stereoselective strategy to gain beta-lactone and oxirane derivatives from kerlinic acid (1) when the β,γ-unsaturated carboxylic acid system is oxidized, preserving the furan moiety. Oxidation of 1 yielded salviaolide (2), suggesting regio- and stereoselective means. A reaction mechanism was proposed when oxidation of the acetate (1a), benzoate (1b), and methyl ester (1c) derivatives from 1 were gained. The obtention of the epoxide derivative 3, kernolide (4), and kernolide epoxide (5) also supported the reaction mechanism. X-ray diffraction analysis of 3, Karplus-type analyses, and DFT calculations from hypothetical intermediates revealed conformational preferences that guide the regioselectivity. The stereoselectivity was attributed to the natural origin of 1. All compounds were characterized by their physical and spectroscopical data. These results suggest the feasibility of promoting regioselective oxidation on neo-clerodane compounds, preserving the furan moiety. Full article

In this study, canola oil was used as a natural enriched source of C18 fatty acids and coconut oil as a natural enriched source of C12 fatty acids. The study synthesized five potassium carboxylate (RCOO⁻K⁺) liquid soaps via saponification of coconut–canola oil blends (100:0, 75:25, 50:50, 25:75, 0:100) using a novel in situ dissolution method with controlled KOH addition to prevent solid paste formation. The water demand required to dissolve RCOO⁻K⁺ and mitigate soap crystallization was determined, increasing from 1.76 to 5.18 g H₂O/g oil as canola oil content rose, with soap concentration decreasing from 55.1% (100:0) to 18.5% (0:100). Reaction kinetics revealed faster KOH depletion in coconut oil-rich blends (100:0, 75:25, 50:50; 2 h) compared to canola oil-rich blends (25:75, 0:100; 8 h). Key soap properties, including foam stability, detergency, wettability, viscosity, and thermal behavior, were assessed. The 50:50 blend exhibited the highest foam stability due to the synergistic effects of medium-chain saturated (e.g., laurates) and long-chain unsaturated (e.g., oleates) RCOO⁻K⁺. The short, saturated chains promoted rapid foam formation, while the longer, unsaturated chains enhanced foam film stability. RCOO⁻K⁺ detergency on hair tresses with artificial sebum ranged from 16.9% to 29.7% and was relatively higher compared to sodium lauryl sulfate, sodium laureth sulfate, cocamidopropyl betaine, and sodium cocoyl glutamate (6.1–13.2%) but lower compared to sodium isethionates (34.2%). RCOO⁻K⁺ wettability on cotton textiles improved with higher coconut oil content. RCOO⁻K⁺ contact angles on artificial sebum surface (6.1–13.7°) demonstrated excellent wettability, effectively penetrating and emulsifying hydrophobic residues. Viscosity ranged from 13–45 mPa·s with Newtonian Flow-type behavior. No crystals were observed in the soaps when cooled in the range of 60 to −30 °C. These results demonstrate RCOO⁻K⁺ soaps as tunable, sustainable liquid soaps with performance optimized by adjusting the oil blend ratios. Full article

A group of renewable, unsaturated resins from itaconic acid, 1,8-octanediol, and succinic anhydride were synthesized in a non-solvent and non-catalyst melt polycondensation reaction. The study addresses the need for sustainable polymeric materials suitable for additive manufacturing by investigating the influence of synthesis parameters—namely itaconic acid content, reaction time, and temperature—on the properties of poly(octamethylene itaconate-co-succinate) (POItcSc). The Box-Behnken mathematical planning method was applied to optimize the reaction conditions. The optimal synthesis conditions of POItcSc were achieved with an itaconic acid molar fraction = 0.50:0.50, reaction time t = 7 h, and reaction temperature T = 150 °C. The conversion of the carboxyl group (by titration) was 83.3%, and the maintenance of C=C bonds (by NMR) was 88.7%. Structural characterization confirmed the formation of the desired polymer through FTIR and ¹H NMR analyses. Molecular weight (M_n = 1001 g/mol for an optimal product), thermal behavior (DSC, TG, DTG), and rheological properties (η = 14.4 and 3.6 Pa∙s for an optimal product at 25 and 36.6 °C) were systematically evaluated. The synthesized POItcSc resins were transparent and exhibited physicochemical properties favorable for extrusion-based 3D printing techniques such as Direct Ink Writing, offering a promising alternative to conventional petrochemical-based inks. Full article

In the thermochemical sulfur–iodine water splitting cycle for hydrogen production, the hydrogen iodide (HI) decomposition reaction serves as the rate-determining step, and its high efficiency relies on the precise design of active sites on the catalyst. This paper combines experimental characterization with density functional theory (DFT) calculations, focusing on activated carbon catalysts. By regulating the types and contents of oxygen-containing functional groups through H₂ reduction treatment at different temperatures, the influence of oxygen-containing functional groups on HI decomposition was investigated. The results show that H₂ reduction treatment can gradually remove oxygen-containing functional groups such as carboxyl, hydroxyl, and carbonyl groups on the surface of activated carbon without significantly affecting the pore structure. Catalytic activity tests conducted under the typical reaction temperature of 500 °C confirmed that as the content of oxygen-containing functional groups decreases, the HI decomposition efficiency increases. DFT calculations further revealed the role of oxygen-containing functional groups: they inhibit the chemisorption of reactant HI on unsaturated carbon atoms and alter the desorption activation energy of product H₂, thereby affecting the overall reaction process. This study provides important theoretical guidance and experimental basis for designing efficient HI decomposition catalysts. Full article

Maximizing the efficient utilization of critical apatite resources through flotation necessitates the exploration of effective and innovative collectors. This study investigates the potential of a fatty acid mixture (FAM) synthesized from saturated palmitic and stearic acids, monounsaturated oleic and palmitoleic acids, and polyunsaturated linoleic acid. The saponified collector FAM and the depressant sodium alginate (NaAl) achieved a direct flotation of apatite from calcite and quartz (97% apatite, 10% calcite, and 7% quartz). The flotation performance with the tested combination exhibited a highly effective enrichment of apatite, mainly from calcite, which aligns with the surface chemistry assessments. Adsorption tests and zeta potential measurements confirmed the micro-flotation results. They provided compelling evidence of a chemisorption interaction between Ca²⁺ sites on calcite and the carboxyl and hydroxyl groups of NaAl. FTIR analyses suggested a reaction between the apatite surface and the carboxyl groups of saturated and unsaturated acid groups in FAM, even those conditioned with NaAl before, facilitating the complex formation. Remarkably, the synergistic effect of the functional groups demonstrates dual functionality, serving as both a hydrophilic entity for calcite and a hydrophobic entity for apatite flotation. The universal mechanism unveils substantial potential for the extensive application of FAM within apatite flotation. Full article

Calendula officinalis L. is a widely used medicinal plant whose secondary metabolism and morphology are influenced by light. This study evaluated the effects of 2 and 4 h end-of-day (EOD) red/far-red (R:FR) and green (G) light on the growth, physiology, and phytochemical profile of hydroponically grown C. officinalis under a constant red/blue light background, compared with a red/blue control without EOD treatment. Morphological, physiological (gas exchange, chlorophyll fluorescence), biochemical (chlorophyll, anthocyanin), and chemical composition (attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and Gas Chromatography-Mass Spectrometry (GC-MS)) were evaluated. EOD G 2 h enhanced photosynthetic pigments, anthocyanins, and biomass, while control plants showed higher phenolic content. EOD R:FR induced stem elongation but reduced pigment and metabolite accumulation. GC-MS revealed organ-specific metabolic specialization, with flowers displaying greater chemical diversity than leaves. EOD G favored sesquiterpene diversity in flowers, while EOD R:FR increased nitrogen-containing compounds and unsaturated fatty acids. Vibrational data supported these shifts, with spectral signatures of esters, phenolics, and lipid-related structures. Bioactive compounds, including α-cadinol and carboxylic acids, were identified across treatments. These findings demonstrate that EOD light modulates physiological and metabolic traits in C. officinalis, highlighting EOD G as an enhancer of biomass and phytochemical richness for pharmaceutical applications under controlled conditions. Full article

The phytochemical profile and antioxidant activities of Prunus africana bark, Leea indica and Paullinia pinnata leaves from Cameroon were investigated in this study. The yields of pure methanolic extraction were 11.9%, 11.1% and 10.8% in P. africana bark, L. indica and P. pinnata leaves, respectively. The total phenolic content was 189.0 ± 16.93, 163.6 ± 14.73 and 114.6 ± 10.38 mg GAE/g and total flavonoid content was 43.25 ± 6.43, 28.31 ± 4.44, and 19.75 ± 4.03 mg RU/g in P. africana bark, L. indica and P. pinnata leaves, respectively. The antioxidant activities of the plants were evaluated by DPPH, ABTS and FRAP assays. The IC₅₀ evaluated in P. africana bark, L. indica and P. pinnata leaves was 109.5 ± 13.2, 132.1 ± 18.7 and 156.1 ± 21.9 µg/mL for DPPH and 98.1 ± 4.8, 101.3 ± 12.1 and 133.9 ± 16.0 µg /mL for ABTS assay. The FRAP value was 61.1 ± 1.5, 50.5 ± 1.5 and 43.4 ± 2.1 µMFe²⁺/g in the same sequence. The functional groups for the corresponding phytochemicals, including alkane, alkene, aliphatic ether, ester, amine, α, β-unsaturated ester, alcohol, phenol, carboxylic acid, and aliphatic ketone, were identified through fourier-transform infrared analysis. The identified and quantified phenolic acids in this study were methyl-4-hydroxybenzoic, caffeic, protocatechuic and p-coumaric acid, identified using high-performance liquid chromatography. Full article

Perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) are emerging contaminants of concern as they persist in natural environments due to their unique chemical structures. This paper critically reviewed the adsorption of PFOA and PFOS, depending on their chemical structure, by different adsorbents as well as soil. Adsorption of PFOS generally surpasses that of PFOA across various adsorbents. Despite having the same number of carbons, PFOS exhibits greater hydrophobicity due to two major structural differences: firstly, it has one extra CF₂ unit and secondly, the sulfonate group in PFOS, being a relatively hard base, readily adsorbs on oxide surfaces, enhancing its adsorption compared to the carboxylate group in PFOA. While comparing activated carbon (AC) adsorption performance, powdered activated carbon (PAC) demonstrates higher adsorption capacity than granular activated carbon (GAC) for PFOS and PFOA. Anion exchange resin (AER) outperforms other adsorbents, with a maximum adsorption capacity for PFOS twice that of PFOA. Carbon nanotubes (CNTs) exhibit two-fold higher adsorption for PFOS compared to PFOA, with single-walled CNTs showing a distinct advantage. Overall, the removal of PFOS and PFOA under similar conditions on different adsorbents is observed to be in the following order: AER > single-walled CNTs > AC. Moreover, AER, single-walled CNTs, and AC exhibited higher adsorption capacities for PFOS than PFOA. In situ remediation studies of PFOA/S-contaminated soil using colloidal activated carbon show a reduction in concentration to below acceptable limits within 12–24 months. The theoretical and experimental studies cited in this review highlight the role of air–water interfacial adsorption in retaining PFOA and PFOS as a function of their charged head groups during their transport in unsaturated porous media. Full article

The availability of water-soluble nanoparticles allows catalytic reactions to occur in highly desirable green environments. The catalytic activity and selectivity of water-soluble palladium nanoparticles capped with 6-(carboxylate)hexanethiolate (C6-PdNP) and 5-(trimethylammonio)pentanethiolate (C5-PdNP) were investigated for the reduction of 4-nitrophenol, the oxidation of α,β-conjugated aldehydes, and the C-C coupling of phenylboronic acid. The study showed that between the two PdNPs, C6-PdNP exhibits better catalytic activity for the reduction of 4-nitrophenol to 4-aminophenol in the presence of sodium borohydride and the selective oxidation of conjugated aldehydes to conjugated carboxylic acids. For the latter reaction, molecular hydrogen (H₂) and H₂O act as oxidants for the surface palladium atoms on PdNPs and conjugated aldehyde substrates, respectively. The results indicated that the competing addition activities of Pd-H and H₂O toward the π-bond of different unsaturated substrates promote either reduction or oxidation reactions under mild conditions in organic solvent-free environments. In comparison, C5-PdNP exhibited higher catalytic activity for the C-C coupling of phenylboronic acid. Gas chromatography–mass spectrometry (GC-MS) was mainly used as an analytical technique to examine the products of catalytic reactions. Full article

Selenium reagents are useful for selenoenzyme-mimicking reactions, as well as for organic synthesis. However, the reaction waste containing selenium frequently smells unpleasant and exhibits serious toxicity. Herein, we have developed new-type on-resin selenium reagents, H-UXX···-PAM (5) and Ac-(X)U*XX···-PAM (6), where U and U* represent selenocysteine (U) and p-methoxybenzyl (PMB)-protected U, respectively, as recyclable catalysts, in which U-containing peptide chains are linked to the polystyrene resin PAM. Synthesized on-resin selenopeptides 5a–g with a variable amino acid sequence were evaluated for their glutathione peroxidase (GPx)-like activity using the UV and ¹H NMR methods, using the reaction between dithiothreitol (DTT^red) and H₂O₂ in methanol. It was found that the intramolecular interaction between U and a basic amino acid residue, such as histidine (H) and lysine (K), enhances peroxidase activity through the formation of an NH···Se hydrogen bond. On the other hand, the catalytic activity of 6a–d was evaluated in the oxidative cyclization of β,γ-unsaturated acids (7) into α,β-unsaturated lactones (8). Although the yield of 8 was significantly decreased after second- or third-round reaction, due to detachment of the selenium moiety from the resin, the results demonstrated reusability, as well as a substrate scope of 6 as a catalyst. Since U is a natural amino acid, on-resin selenopeptides are potential targets as novel-type green redox catalysts. Full article