Search Results (4,033)

The synthetic strategy relies on the highly diastereoselective alkylation at the C4 position of L-pyroglutamic acid derivatives, followed by a decarboxylation-allylation process that enables the incorporation of diverse substituents, including aromatic substituents, affording trans-3,5-disubstituted γ-lactams with excellent diastereiosmeric ratio (dr > 98:2). The resulting γ-lactams were efficiently transformed into a series of α,γ-disubstituted γ-amino acids through hydrogenation and acidic hydrolysis. Furthermore, cross-metathesis reactions with styrene and 1-decene enabled the introduction of structurally diverse lipophilic side chains, furnishing the corresponding γ-amino acids in good overall yields (71–77%) and high diastereoisomeric ratio from >98:2 to 92:8. In addition, N-allylation followed by ring-closing metathesis and hydrogenation provided access to a previously unexplored conformationally constrained γ-amino acid. Overall, seven α,γ-disubstituted γ-amino acids, including fluorinated and conformationally restricted derivatives, were synthesized from common intermediates with high stereocontrol. The developed methodology offers a versatile platform for the preparation of structurally diverse and underexplored γ-amino acid building blocks of potential interest in peptide synthesis, medicinal chemistry, and antimicrobial agent development. Full article

This work aims to investigate the interfacial tension characteristics of alkyl carboxymethyl betaines dispersed at the crude oil/formation water interface. Four alkyl dimethyl carboxymethyl betaines and one alkyl diethyl carboxymethyl betaine were synthesized, then the effects of surfactant molecular structure, crude oil component, and inorganic salt composition of formation water on interfacial tensions were studied systematically. The results show that the synthesized octadecyl diethyl carboxymethyl betaine has the highest interfacial activity and exhibits superior anti-dilution performance. In the presence of polyacrylamide, this betaine also displays good anti-adsorption capability. With respect to crude oil components, the resin component, especially the petroleum acid and alkali components, play important roles in tension reduction. For formation water, its alkaline inorganic salts are crucial to obtain an ultra-low interfacial tension by its saponification effect on petroleum acid. The octadecyl diethyl carboxymethyl betaine also exhibits good temperature and salt resistance, but poor tolerance toward divalent cations owing to the consumption of alkaline inorganic salts. Moreover, it is found that there exists synergism between octadecyl diethyl carboxymethyl betaine and dodecylbenzene sulfonate which can further reduce the interfacial tension. The above findings are conducive to the selection of betaine surfactants in chemical flooding. Full article

Low-rank ultrafine flotation clean coal typically yields filter cake moisture above 20% due to abundant oxygen-containing functional groups and strong surface hydrophilicity. Conventional polyacrylamide (PAM) flocculants are hydrophilic and improve dewatering only by altering cake porosity, not by reducing particle surface hydrophilicity, so they remove little adsorbed water. In this study, hydrophobically modified anionic polyacrylamides (HMAPAM) were synthesized by grafting lauryl acrylate onto APAM. FTIR, ¹H NMR, XPS, and SEM confirmed the grafting and progressive enrichment of hydrophobic alkyl chains on the surface. Moderate hydrophobic modification markedly improved solid–liquid separation. HMAPAM-D (APAM/LA = 4.5:0.5) achieved a settling velocity of 0.817 cm/s at 9 mg/L, 50.2% higher than APAM, and reduced filter cake moisture to 16.64% at 1 mg/L under 0.6 MPa versus 19.39% for unmodified APAM. Excessive modification (HMAPAM-E, 4:1) promoted intramolecular self-association, producing heterogeneous flocs and higher filtration resistance that degraded dewatering efficiency. The performance gain stems from hydrophobic association combined with adsorption bridging. These results clarify how hydrophobic group content controls flocculation and dewatering, informing the design of better flocculants for this type of coal slurry. Full article

FDO’s wide boiling range and complex composition hinder controlled synthesis of high-performance mesophase pitch. Here, FDO was separated into light, middle, and heavy narrow fractions by vacuum distillation. Multi-scale characterization traced molecular evolution and mesophase development. The light fraction consists of three-ring aromatics with short alkyl side chains and shows the lowest reactivity, yielding limited condensation and poor stacking with isotropic regions and dispersed spheres. The middle fraction contains four-ring aromatics with moderately extended chains, exhibiting enhanced reactivity and undergoing nucleation, growth, coalescence, and disintegration of mesophase spheres. However, insufficient volatiles restrict shear orientation, forming a mosaic texture. The heavy fraction has four-ring aromatics with the longest alkyl chains and the lowest substitution degree, giving the highest reactivity. During thermal cracking, long chains release abundant radicals and volatiles; directional escape generates shear, promoting rapid growth and ordered alignment of aromatic lamellae. At 440 °C for 12 h, this fraction yields high-quality mesophase pitch with small-domain texture, a low softening point (295 °C), and high anisotropic content (98.8%). The pitch shows excellent spinnability, and derived carbon fibers (tensile strength ~1.45 GPa, modulus ~151 GPa) outperform a commercial reference processed under identical conditions. This study reveals molecular-level regulation of mesophase evolution by narrow fraction structures. Full article

Balancing ionic transport, thermal robustness, and electrochemical stability remains an important challenge in the design of ionic liquid (IL) electrolytes for lithium-based energy storage. Here, quantitative structure–transport relationships were established through a systematic comparison of six bis(trifluoromethanesulfonyl)imide ([Tf₂N]⁻)-based ILs spanning imidazolium, pyrrolidinium, and quaternary ammonium cation families, each examined in both conventional alkyl and ether-functionalized forms. Density, viscosity, and ionic conductivity were measured over broad temperature ranges, while Raman spectroscopy and electrochemical stability measurements were used to probe ion association and voltage stability under selected conditions for both neat ILs and LiTf₂N-containing electrolytes. Ether functionalization consistently lowered viscosity and enhanced conductivity in the neat ILs, whereas LiTf₂N addition markedly increased viscosity and reduced conductivity in all systems. The magnitude of this lithium-induced transport penalty depended on cation architecture, being smallest for imidazolium systems and largest for ammonium analogues. Raman spectra indicate that these trends are associated with competition between Li⁺–anion coordination and ether-mediated solvation, which modifies ion association and local coordination environments. Walden analysis showed subionic behavior for all systems, with larger deviations after lithium incorporation, suggesting increased ion correlation. Electrochemical measurements revealed a complementary trade-off between transport and stability: the ether-functionalized imidazolium electrolyte containing 0.65 mmol g⁻¹ LiTf₂N exhibited the highest ionic conductivity among the lithium-containing systems, reaching 1.6 and 12.6 mS cm⁻¹ at 25 and 80 °C, respectively, but the corresponding imidazolium IL had the narrowest electrochemical stability window, about 4.3 V. In contrast, the ether-functionalized pyrrolidinium and ammonium ILs exhibited wider electrochemical stability windows of about 5.5 V, with improved cathodic stability and somewhat higher anodic stability than the imidazolium analogue. Full article

Chinese lacquerware is a multi-layered natural polymer composite whose characterization is complicated by burial degradation, organic–inorganic mixing, and the overlap of signals from lacquer, drying oils, proteins, polysaccharides, waxes, and pigments. This review evaluates analytical strategies for Chinese lacquerware by distinguishing three complementary levels of evidence: morphological and elemental observation, chemically specific molecular fingerprinting, and biomolecular source recognition. Microscopy, Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and scanning electron microscopy–energy dispersive spectroscopy (SEM-EDS) are useful for identifying stratigraphy, pigments, fillers, and functional groups, but they are often insufficient for assigning degraded organic matrices and trace additives independently. Pyrolysis–gas chromatography/mass spectrometry provides more specific molecular evidence through diagnostic marker classes, including alkyl catechols, alkyl phenols, nitrogen-containing pyrolysis products, anhydrosugars, long-chain aliphatics, aldehydes, and ketones. Immunological assays based on lacquer glycoproteins further complement chemical analysis by supporting biological source differentiation, although their reliability depends on protein preservation, extraction efficiency, and antibody specificity. Representative case studies, including a seventeenth-century Swedish lacquered pipe, the Nanyue Kingdom lacquered ear cup, and a Tang Dynasty lacquered leather artifact, show that robust interpretation requires cross-validation among stratigraphic, elemental, spectroscopic, chromatographic, immunological, and archaeological evidence. The review concludes that integrated analytical workflows can improve material identification, clarify manufacturing sequences, assess degradation uncertainty, and provide more reliable evidence for conservation decision-making and the reconstruction of historical lacquer craftsmanship. Full article

4-Methyl-N-(4-methylbenzyl)-N’-(4-methylbenzylidene)benzenesulfonohydrazide was synthesized via N-alkylation. The compound was characterized by nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry (MS). Its molecular structure was unambiguously established by single-crystal X-ray diffraction analysis. The comprehensive spectral and crystallographic data conclusively verify the successful synthesis and structural integrity of this newly prepared compound. Full article

Aliphatic diamines possess two amino functional groups and exhibit diverse chemical properties and tunable molecular structures. By selecting the guest [(C₂H_2n+4N₂), n = 2–6] and host 18-crown-6, and controlling the design and assembly processes via modulation by thiocyanate and a manganese salt, a series of dumbbell-shaped crown ether complexes, (C₂H_2n+6N₂)²⁺(18-crown-6)₂[Mn(NCS)₄]²⁻·(δ_n,₂C₂H₃N), n = 2–6, (1)–(5), was synthesized and analyzed by single-crystal X-ray diffraction (SCXRD) at 100 K and 293 K. Variable-temperature infrared and XRD analyses confirmed that compounds 3 and 5 underwent a phase transition. As the length of the carbon chain increases and alternates between odd and even, the interplanar dihedral angle of the crown ether exhibits a distinct pattern: Even-number chains arrange in parallel, whereas odd-number chains form a pronounced angle. This structural pattern influences macroscopic deformation of the crystal and induces corresponding periodic variations in the dielectric and electrochemical properties. The wide-bandgap insulators and magnetic properties are primarily governed by the inorganic components of the system and are less influenced by the organic portion. This study reveals principles for regulating supramolecular conformation and functional properties through the parity of the organic chain lengths, providing a strategy for the molecular-level design of supramolecular crystal materials with ordered structures and tunable properties. Full article

Five pH- and light-switchable punicine derivatives were investigated as collectors in the flotation of spodumene and quartz. At the natural pH of the minerals, the punicine substituted with a C17 alkyl residue showed the best recovery under daylight (>5000 lux), with values up to 65.0% and 97.8%, and also the highest absolute recovery difference between the two minerals. For pH values of 2 and 12, the punicine collector with a viologen moiety and a C9 alkyl residue shows the best absolute recovery difference, with values of 32.45% and 32.88%, respectively. Studies on the influence of pH, particle size distribution, UV light and darkness, ζ-potential measurements, and IR spectroscopic measurements were carried out to gain insight into the mechanisms. Full article

Transfer hydroformylation of alkenes with formaldehyde constitutes a green and sustainable route to aldehydes. In this work, the transfer hydroformylation of styrene with formaldehyde was efficiently catalyzed by [Rh(κ²-dppe)₂]⁺ (A), where dppe stands for 1,2-bis(diphenylphosphino)ethane. The reaction was found to be first order with respect to both Rh and substrate concentrations and fractional order with respect to formaldehyde concentration, in line with the behavior previously reported for 1-hexene. DFT was used to investigate the reaction mechanism by using ethene and [Rh(κ²-dpe)₂]⁺ (A), where dpe stands for 1,2-bis(phosphine)ethane, as simplified models of the substrate and catalyst, respectively, and by considering several functionals. The DFT calculations indicate that M06-L provides the most suitable description of the thermodynamic and activation parameters associated with the elementary steps. The combined analysis of kinetic results and the DFT calculations allowed us to propose a detailed catalytic cycle for this reaction, initiated by the reversible oxidative addition of formaldehyde to complex A to afford [Rh(H)(CHO)(κ²-dppe)₂]⁺ (B, ${\mathit{K}}_{\mathbf{1}}$). Coordination of ethene occurs through partial dissociation of one phosphorus atom of the diphosphine ligand, generating [Rh(H)(alkene)(CHO)(κ²-dppe)(κ¹-dppe)]⁺ (I_B, ${\mathit{K}}_{\mathbf{2}}$), followed by the transfer of the hydride to the alkene to give [Rh(alkyl)(CHO)(κ²-dppe)₂]⁺ (C, ${\mathit{k}}_{\mathbf{3}}$), which is considered the rate-determining step of the process. The cycle is completed by reductive elimination of propanal, thereby regenerating A. The overall activation energy calculated by DFT (Ea = 20.0 kcal mol⁻¹) is in good agreement with the experimental values determined for 1-hexene and styrene (20.1 and 22.9 kcal mol⁻¹, respectively). On the basis of these experimental and DFT results, a mathematical kinetic model with the canonical form $r_0={{\mathit{K}}_{\mathbf{1}}{\mathit{K}}_{\mathbf{2}}\mathit{k}}_{\mathbf{3}}{\left[Rh\right]}_o\left[alkene\right]\left[C{H}_{2}O\right]/\left({1+\mathit{K}}_{\mathbf{1}}\left[C{H}_{2}O\right]\right)$ was developed and fitted using a tandem LMFit/Bayesian approach, allowing the values of K₁ and K₂k₃ to be estimated, with comparatively low uncertainty. Overall, this integrated kinetic, computational, and statistical study provides a consistent mechanistic and quantitative framework for understanding the transfer hydroformylation of alkenes with formaldehyde. Full article

Achieving strong adhesion in underwater or humid environments remains challenging because the interfacial hydration layer prevents direct contact between the adhesive and the substrate. Conventional adhesives typically fail under these conditions, so new strategies are needed to actively displace the water layer and create stable interfacial interactions. In this study, we prepared a series of copolymers with different monomer ratios via photocuring, using methacrylic acid (MAA) and stearyl methacrylate (SMA) as monomers. We focused on their thermal transition behavior and adhesion performance under both dry and underwater conditions. The results show that at an SMA molar fraction of 85%, the copolymer exhibits crystalline melting between 30 and 40 °C, where the storage modulus drops from approximately 10⁷ Pa to 10⁴ Pa, indicating a stiff-to-soft transition. Under dry conditions, this composition shows an adhesion strength of 1.67 MPa to glass, which remains 1.2 MPa underwater, and it can support a hanging load of 5 kg. The copolymer adheres well to glass and aluminum but shows weak adhesion to PTFE. After surface abrasion, the adhesion strength to glass increases to 1.6–1.8 MPa. In summary, the copolymer achieves effective underwater adhesion through the synergy of hydrophobic water displacement, thermally induced stiff-to-soft switching, and hydrogen bonding. Full article

Alkanes are saturated hydrocarbons that serve as available and cost-effective feedstock for producing alkenes, key intermediates in numerous industrial processes. A mutant bacterial strain, Rhodococcus sp. KSM-B-3M, was previously reported to efficiently convert alkanes into alkenes and was later utilized by us to selectively transform linear alkanes into a variety of alkyl derivatives through a two-step process. Here, we explored the biological mechanisms underlying the unique biotransformation capability of strain KSM-B-3M by integrating genomics, transcriptomics, proteomics, and 3D-structural modelling. Strain KSM-B-3M demonstrated downregulation of the fatty acid degradation pathway, lacking the pR8L1 megaplasmid that carries multiple fatty acid degradation genes, accompanied by a parallel high expression of the acyl CoA-desaturase gene. Partial curing of the pR8L1 plasmid from a wild-type (WT) strain conferred the ability to dehydrogenate n-hexadecane to cis-hexadecene. Overexpression of the acyl-CoA desaturase gene similarly induced cis-hexadecene formation in the WT strain, acting cumulatively with fatty acid degradation downregulation. Acyl CoA-desaturase 3-D modeling suggested that the enzyme directly dehydrogenates n-hexadecane to form cis-hexadecene, supporting its direct role in this unique biotransformation. These findings advance our understanding of the mechanism behind this biotransformation, which holds promise for sustainable and cost-effective production of alkyl derivatives. Full article

Ether lipids in varying amounts are membrane constituents and storage material in the protist and animal kingdoms, but are largely absent from fungi and plants. Their biosynthesis pathway starts in the peroxisome and involves a set of well-conserved enzymes. Only one step, the reduction of alkyl-dihydroxyacetone-phosphate to alkyl-glycerol-3-phosphate, is mediated by so-called short-chain dehydrogenases/reductases, which are members of huge protein families. Here, using GFP fusions, we identify a peroxisomal enzyme in Dictyostelium, as well as a highly related protein residing in the endoplasmic reticulum. Single-gene knockouts indicate that these enzymes largely compensate for one another, suggesting a flexible redistribution of lipid metabolites between these organelles. The double knockout, however, is severely affected in ether lipid composition and displays a clear growth retardation. The defects can also be reverted by expression of the cognate yeast enzyme, demonstrating conservation of this metabolic step across kingdoms of life. Full article

Pomegranate peel, an abundant agro-industrial by-product, represents a sustainable source of bioactive polyphenols, particularly punicalagin, which has been associated with antioxidant and photoprotective potential. This study aimed to develop microemulsions (MEs) containing pomegranate peel extract for dermal delivery of punicalagin using biocompatible surfactant systems. Three MEs differing in surfactant–cosurfactant composition (ME-A, ME-P, and ME-E) were prepared. Each formulation solubilized 1% (w/w) of pomegranate peel extract and was evaluated regarding in vitro release behavior, skin permeation/retention, antioxidant activity, and in vitro sun protection factor (SPF). All investigated MEs provided sustained release of punicalagin (≈10–17% of the applied dose in 8 h). ME-A, based on an alkyl polyglucoside surfactant, showed a significantly higher cumulative release of punicalagin (60.4 µg/cm²) compared with ME-E and ME-P. In skin penetration/permeation studies, ME-A also exhibited the highest numerical total delivery of punicalagin (≈48.2 µg/cm² after 24 h), although differences among formulations were not statistically significant. All formulations demonstrated high antioxidant activity in the DPPH assay and measurable in vitro photoprotective potential, with SPF values ranging from approximately 11 to 14. Overall, pomegranate peel extract-loaded MEs showed potential as dermal delivery systems capable of improving solubilization and modulating skin delivery of punicalagin. The combination of agro-waste-derived bioactives with biocompatible surfactants highlights the potential of these systems as sustainable approaches for skincare formulations. Full article

Reducing hospital-acquired infections, especially those related to medical devices, is essential not only to improve patients’ well-being but also to reduce healthcare costs. Among various antibacterial approaches, creating bactericidal device surfaces has been advocated as it reduces the likelihood of antibiotic-resistant strains emerging when antibiotics are used. Functionalizing the device surface with cationic groups, such as quaternary ammonium terminal groups, has been considered an effective approach for killing microbes upon contact. Nonetheless, multiple steps, some of which may require harsh chemical reactions and toxic solvents, are generally required to attach the cationic quaternary ammonium functionalities to the surface. Inspired by the mussel’s capability to bind to various substrates, various novel biomimetic cationic catechol-terminated small molecules having the quaternary ammonium functionality with different alkyl chain lengths were synthesized for the first time. These compounds were used for surface modification of medical-grade titanium using simple immersion approaches: a single-layer procedure or a two-layer approach, in which the first layer was prepared by dopamine immersion, followed by a second immersion in the compound of interest. The surface characteristics and antimicrobial capability against the Gram-negative E. coli and Gram-positive S. aureus were assessed. The likely effects of the alkyl chain length and modification schemes on the surface properties and antibacterial activity are discussed and compared. The highest antimicrobial activity against E. coli was noted on the modified surfaces prepared by the two-layer approach with the cationic compound having the shortest alkyl chain, C1, at 2 mg/mL (DA_C1-2) and 8 mg/mL (DA_C1-8). The DA_C1-8 surface also exhibited the highest antimicrobial activity against S. aureus. These findings indicated that the antibacterial activity of titanium can be greatly improved by selecting the appropriate compound and a proper, facile immersion procedure. Full article