Search Results (1,050)

Rizhao green tea (RZT), a renowned green tea, is cultivated in China’s northernmost tea region. Its unique environment endows it with a strong chestnut- and seaweed-like aroma. This study sought to explore the volatile profiles of RZT and pinpoint its key odorants by employing stir bar sorptive extraction (SBSE) coupled with gas chromatography–mass spectrometry (GC-MS), determining the odor activity value (OAV), and performing gas chromatography–olfactometry (GC-O). A total of 112 volatiles were identified, and the major volatile compounds were esters (2035.25 μg/kg), alcohols (1799.02 μg/kg), alkanes (991.88 μg/kg), and ketones (691.96 μg/kg), comprising 74.91% of the total. A molecular aroma wheel was preliminarily established based on these key odorants. These insights might contribute to the scientific elucidation of the flavor chemical basis of RZT. Full article

On-board emission measurements were conducted at the exhaust of a passenger ship operating under real-world conditions. The chemical composition of exhaust particulate emissions from a turbocharged four-stroke marine diesel engine, operated on Marine Gas Oil was studied. A variety of organic compounds, including alkanes, alkenes, alcohols, cycloalkanes, cycloalkenes, esters, ketones, carboxylic acids, etc., were analyzed. Alkanes were the most abundant organic compounds, followed by alkenes, esters, and alcohols. Emission factors for these compounds were determined under two operating conditions: low engine load (at berth at 400 rpm/4% load, and during port maneuvers at 800 rpm/14% load) and high engine load (during cruising at 1000 rpm, 68% load). A clear increase in organic-compound emission factors was observed at lower loads. The total particulate matter emission factors were between 0.02 and 0.03 g/kWh at high-load points and exhibited significant variability under low-load conditions, from 0.02 to 2.83 g/kWh. The effect of a marine fuel additive was evaluated in this study. Using this fuel additive resulted in a significant decrease in both particulate matter and organic-compound emission factors, especially at low engine loads. Furthermore, the marine fuel additive decreased the total emission factors (EF_TOCs) by a factor of 56 under low-load conditions. For high loads, the additive had no effect on the EF_TOCs. Full article

The genus Hypericum (Hypericaceae), comprising approximately 500 taxa classified into 22 sections, has remained largely unexplored in terms of its chemical composition, with existing studies on a limited number of species revealing significant chemical polymorphism. This study investigates the volatile profiles of four Hypericum species (H. rumeliacum subsp. apollinis, H. vesiculosum, H. delphicum, and H. olympicum) through GC-MS analysis. Hypericum rumeliacum subsp. apollinis, collected from Mt. Parnassos, exhibited a high abundance of sesquiterpenes hydrocarbons (32.5%) and oxygenated sesquiterpenes (29.7%). Hypericum vesiculosum collected from Mt. Chelmos was rich in oxygenated monoterpenes (33.5%), followed by benzyl derivatives (25.9%). Hypericum delphicum and H. olympicum, collected from the island of Evvia, showed a predominance of alkanes (35.8%) and oxygenated sesquiterpenes (31.9%) in H. delphicum and sesquiterpenes hydrocarbons (41.2%) and oxygenated sesquiterpenes (29.9%) in H. olympicum. Our findings provide new data on the volatile profile of H. vesiculosum and enhance existing information on other species, highlighting notable chemical diversity within the genus Hypericum. Full article

A comprehensive understanding of the compositions and physicochemical properties of coal-based liquids is conducive to the rapid development of multipurpose, high-performance, and high-value functional chemicals. However, because of their complex compositions, coal-based liquids generate two-dimensional gas chromatography (GC × GC) chromatograms that are very complex and very time consuming to analyze. Therefore, the development of a method for accurately and rapidly analyzing chromatograms is crucial for understanding the chemical compositions and structures of coal-based liquids, such as direct coal liquefaction (DCL) oils and coal tar. In this study, DCL oils were distilled and qualitatively analyzed using GC × GC chromatograms. A deep-learning (DL) model was used to identify spectral features in GC × GC chromatograms and predominantly categorize the corresponding DCL oils as aliphatic alkanes, cycloalkanes, mono-, bi-, tri-, and tetracyclic aromatics. Regional labels associated with areas in the GC × GC chromatograms were fed into the mask-region-based convolutional neural network’s (Mask R-CNN’s) algorithm. The Mask R-CNN accurately and rapidly segmented the GC × GC chromatograms into regions representing different compounds, thereby automatically qualitatively classifying the compounds according to their spots in the chromatograms. Results show that the Mask R-CNN model’s accuracy, precision, recall, F1 value, and Intersection over Union (IoU) value were 93.71%, 96.99%, 96.27%, 0.95, and 0.93, respectively. DL is effective for visually comparing GC × GC chromatograms to analyze the compositions of chemical mixtures, accelerating GC × GC chromatogram interpretation and compound characterization and facilitating comparisons of the chemical compositions of multiple coal-based liquids produced in the coal and petroleum industry. Applying DL to analyze chromatograms improves analysis efficiency and provides a new method for analyzing GC × GC chromatograms, which is important for fast and accurate analysis. Full article

The current paradigm of low-T combustion and autoignition of hydrocarbons is based on the sequential two-step oxygenation of fuel radicals. The key chain-branching occurs when the second oxygenation adduct (OOQOOH) is isomerized releasing an OH radical and a key ketohydroperoxide (KHP) intermediate. The subsequent homolytic dissociation of relatively weak O–O bonds in KHP generates two more radicals in the oxidation chain leading to ignition. Based on the recently introduced intramolecular “catalytic hydrogen atom transfer” mechanism (J. Phys. Chem. 2024, 128, 2169), abbreviated here as I-CHAT, we have identified a novel unimolecular decomposition channel for KHPs to form their classical isomers—enol hydroperoxides (EHP). The uncertainty in the contribution of enols is typically due to the high computed barriers for conventional (“direct”) keto–enol tautomerization. Remarkably, the I-CHAT dramatically reduces such barriers. The novel mechanism can be regarded as an intramolecular version of the intermolecular relay transfer of H-atoms mediated by an external molecule following the general classification of such processes (Catal. Rev.-Sci. Eng. 2014, 56, 403). Here, we present a detailed mechanistic and kinetic analysis of the I-CHAT-facilitated pathways applied to n-hexane, n-heptane, and n-pentane models as prototype molecules for gasoline, diesel, and hybrid rocket fuels. We particularly examined the formation kinetics and subsequent dissociation of the γ-enol-hydroperoxide isomer of the most abundant pentane-derived isomer γ-C5-KHP observed experimentally. To gain molecular-level insight into the I-CHAT catalysis, we have also explored the role of the internal catalyst moieties using truncated models. All applied models demonstrated a significant reduction in the isomerization barriers, primarily due to the decreased ring strain in transition states. In addition, the longer-range and sequential H-migration processes were also identified and illustrated via a combined double keto–enol conversion of heptane-2,6-diketo-4-hydroperoxide as a potential chain-branching model. To assess the possible impact of the I-CHAT channels on global fuel combustion characteristics, we performed a detailed kinetic analysis of the isomerization and decomposition of γ-C5-KHP comparing I-CHAT with key alternative reactions—direct dissociation and Korcek channels. Calculated rate parameters were implemented into a modified version of the n-pentane kinetic model developed earlier using RMG automated model generation tools (ACS Omega, 2023, 8, 4908). Simulations of ignition delay times revealed the significant effect of the new pathways, suggesting an important role of the I-CHAT pathways in the low-T combustion of large alkanes. Full article

Polyethylene (PE) is a widely used material for packaging food. However, certain additives and their degradation products, which may be generated during transformation processes, may pose risks to consumers health if they migrate into food at levels exceeding safety thresholds. Therefore, identifying and quantifying these potential migrant compounds is crucial to ensuring consumer safety. In the present work, PE films and the raw materials used in their production were kindly provided by the industry to evaluate undesired compounds throughout the PE transformation chain. For that purpose, volatile and semi-volatile organic compounds were evaluated using gas chromatography coupled to mass spectrometry (GC-MS). Alkanes were identified as the most abundant compounds, along with antioxidants, lubricants, or Non-Intentionally Added Substances (NIAS), like 7,9-di-tert-butyl-1-oxaspiro(4,5)deca-6,9-diene-2,8-dione in the films. For the unidentified compounds, evaluations were conducted at various stages of the transformation chain, and migration assays were performed to assess their behavior. Full article

This research employs 2-methylene-tetrahydronaphtalene-1-ones and N-cyclopropylanilines as starting materials, integrating photocatalysis and organic phosphoric acid catalysis to synthesize 2-amino-spiro[4.5]decane-6-ones via a [3 + 2] cycloaddition approach. This method boasts the advantage of mild reaction conditions that are photocatalyst-free and metal catalyst-free. It achieves 100% atom conversion of the substrates, aligning with the principles of green chemistry. Additionally, it attains a high diastereoselectivity result of up to 99:1, demonstrating good stereoselectivity. In the derivatives of 2-methylene-tetrahydronaphtalene-1-ones, substrates with alkane rings of different sizes or thiophene replacing the phenyl ring are also amenable to this method, enabling the synthesis of different [4.4], [4.5], and [4.6] spirocyclic compounds. In the derivatives of N-cyclopropylanilines, substrates with para-fluoro and meta-fluoro substitutions are also amenable to this method. Finally, a preliminary mechanistic investigation was conducted, proposing a plausible reaction mechanism pathway initiating from the intermediate N-cyclopropylanilines with chiral phosphoric acid. Full article

Optically responsive materials are applied in sensing, actuators, and optical devices. One such class of material is dye-doped liquid crystal polymers that self-assemble into cholesteric mesophases that reflect visible light. We report here the synthesis and characterization of a family of linear and mildly crosslinked terpolymers prepared by the ROMP of norbornene-based monomers. The three monomers were composed of (i) rhodamine dye through one or two norbornene end groups utilizing flexible C₁₀-alkane spacers, (ii) a cholesteryl liquid crystal (LC) using C₉-alkane spacers, and (iii) PEG side chains. We investigated how these architectural variations in these terpolymers impacted their hierarchically self-assembled mesophase properties. We probed their composition, morphology, thermal, mechanic, photochromic, and mechanochromic properties using, inter alia, ¹H NMR spectroscopy, DSC, temperature-dependent SAXS, diffuse reflectance UV-vis spectroscopy, and optical polarization microscopy. The new terpolymers exhibited architecture-dependent thermochromic, mechanochromic, and piezochromic properties arising from LC–rhodamine dye interactions. We found that a compromise between the rigidity and flexibility of the terpolymer architectures needed to be stricken to fully express stimuli-responsive properties. These terpolymers also showed distinctly different properties compared to those of a previously reported structurally related liquid crystalline copolymer made from two monomers. These findings help to define the design principles for optimally stimuli-responsive liquid crystalline polymers. Full article

The properties of starch graft poly(cinnamyl methacrylate) copolymers were presented. The “grafting from” method and different ratios of starch to methacrylic monomer were used. The copolymers with the maximum grafting percent (G: 55.3% ± 0.4) using a ratio of starch to methacrylic monomer of 1:3 were obtained. The heterogeneous, non-porous structure materials were prepared. They were characterized by significant lower swelling in polar solvents and moisture absorption but higher swelling in non-polar solvents compared to unmodified potato starch. The chemical resistance in acidic, alkaline and neutral environments for all the tested copolymers was significantly higher compared to the chemical resistance of potato starch. The tested copolymers decomposed in at least three main stages in inert conditions and in at least four main stages in oxidative conditions. Their pyrolysis with the emission of the mixture of volatiles such as aldehyde, acid, ester, alcohol, aromatic, alkene, alkane, H₂O, CO₂ and CO based on the TG/FTIR studies was proved. The oxidative decomposition included pyrolysis processes combined with oxidation and combustion reactions of volatiles and the formed residues. As a result, the emission of the unsaturated and saturated compounds with carbonyl, hydroxyl, carboxyl and/or ester groups, alkane, alkene, aromatics and its oxidized forms, H₂O, CO₂ and CO, was observed. Full article

Crude oil pollution of soil is an important issue that has serious effects on both the environment and human health. Phytoremediation is a promising approach to cleaning up oil-contaminated soil. In order to facilitate phytoremediation effects for oil-contaminated soil, this study set up a pot experiment to explore the co-application potentiality of Tagetes erecta L. with two other methods: microbial agent and biochar. Results showed that the greatest total petroleum hydrocarbon (TPH) biodegradation (76.60%) occurred in the soil treated with T. erecta, a microbial agent, and biochar; the highest biomass and root activity also occurred in this treatment.GC-MS analysis showed that petroleum hydrocarbon components in the range from C₁₀ to C₄₀ all reduced in different treatments, and intermediate-chain alkanes were preferred by our bioremediation methods. Compared with the treatments with biochar, the chlorophyll fluorescence parameter NPQ_Lss and plant antioxidant enzyme activities significantly decreased in the treatments applied with the microbial agent, while soil enzyme activities, especially oxidoreductase activities, significantly increased. Although the correlation between biochar and most plant growth and soil enzyme activity indicators was not significant in this study, the interaction effect analysis found a synergistic effect between microbial agents and biochar. Overall, this study suggests the co-addition of microbial agents and biochar as an excellent method to improve the phytoremediation effects of oil-contaminated soil and enhances our understanding of the inner mechanism. Full article

Five representatives of a novel type of di(hydroperoxy)alkane adducts of phosphine oxides have been synthesized and fully characterized, including their solubility in organic solvents. The phosphine oxide Cy₃PO (1) has been used in combination with the corresponding aldehydes to create the adducts Cy₃PO·(HOO)₂CHCH₃ (2), Cy₃PO·(HOO)₂CHCH₂CH₃ (3), Cy₃PO·(HOO)₂CH(CH₂)₂CH₃ (4), Cy₃PO·(HOO)₂CH(CH₂)₃CH₃ (5), and Cy₃PO·(HOO)₂CH(CH₂)₇CH₃ (6). All adducts crystallize easily and contain the peroxide and phosphine oxide hydrogen-bonded in 1:1 ratios. The single crystal X-ray structures of 2–6 and their unique features are discussed. The ³¹P NMR spectra of the adducts 2–6 show downfield-shifted signals as compared to Cy₃PO. In the IR spectra, the ν(P=O) wavenumbers of the adducts have smaller values than the neat phosphine oxide. All spectroscopic results of 2–6 show that the P=O bond is weakened by hydrogen-bonding to the di(hydroperoxy)alkane moieties. Adduct 6 selectively oxidizes PPh₃ to OPPh₃ within minutes, and nonanal is reformed in the process. The easy synthesis, handling, and administration of these stable, solid, and soluble peroxides with well-defined composition will have a positive impact on synthetic chemistry. Full article

The biological and thermal properties of a class of synthetic dihydroimidazotriazinones were disclosed in this article for the first time. Molecules 1–6—as potential innovative antimetabolites mimicking bicyclic aza-analogues of isocytosine—were evaluated for their in vitro anticancer activity. Moreover, in vivo, in vitro, and ex vivo toxicity profiles of all the compounds were established in zebrafish, non-tumour cell, and erythrocyte models, respectively. Their antihaemolytic activity was also evaluated. Additionally, the thermal decomposition mechanism, path, and key thermal properties of heterocycles 1–6 were analysed. It was found that all the studied compounds revealed significant antiproliferative activities against tumour cells of the lung, cervix, ovary, and breast, as well as acute promyelocytic leukaemia cells, superior or comparable to that of an anticancer agent gemcitabine. Most of them were less toxic to non-tumour cells than this standard drug, and none had a haemolytic effect on red blood cells. All the tested heterocycles proved to be safer for zebrafish than a standard drug pemetrexed. Some exhibited the ability to inhibit oxidative haemolysis, suggesting their protective action on erythrocytes. The differential scanning calorimetry (DSC) analyses confirmed that all molecules melted within one narrow temperature range, proving their purity. The melting points depended solely on the type of substituent and increased as follows: 4 (R = 3-ClPh) < 2 (R = 4-CH₃Ph) = 3 (R = 4-OCH₃Ph) < 5 (R = 4-ClPh) = 1 (R = Ph) < 6 (R = 3,4-Cl₂Ph). The thermogravimetry/differential thermogravimetry (TG/DTG) studies confirmed high thermal stability of all the investigated heterocycles in inert (>230 °C) and oxidising (>260 °C) atmospheres, which depended directly on the R. The pyrolysis process included one main decomposition stage and was connected with the emission of NH₃, HCN, CH₃CN, HNCO, alkane, alkene, aromatic fragments, CO₂ (for all the compounds), and HCl (for the molecule with 3,4-Cl₂Ph), which was confirmed by FTIR and QMS analyses. In turn, the oxidative decomposition process of the tested polyazaheterocycles took place in two main stages connected with the formation of the same volatiles as those observed in an inert atmosphere and additionally with the release of N₂, NO, CO, and H₂O. These results proved that the pyrolysis and oxidative decomposition run through the radical mechanism connected with the additional reactions between radicals and oxygen in synthetic air. The favourable biological and thermal properties of this class of dihydroimidazotriazinones imply their usefulness as potential pharmaceutics. Full article

Shale oil reservoirs feature a considerable number of nanopores and complex minerals, and the impact of nano-pore confinement and pore types frequently poses challenges to the efficient development of shale oil. For shale oil reservoirs, CO₂ flooding can effectively lower crude oil viscosity, enhance reservoir physical properties, and thereby increase recovery. In this paper, the CO₂ displacement process in the nanoscale pores of shale oil was simulated through the molecular dynamic simulation method. The performance disparity of quartz and calcite slit nanopores was discussed, and the influences of nanoscale pore types and displacement rates on CO₂ displacement behavior were further analyzed. The results demonstrate that the CO₂ displacement processes of different inorganic pores vary. In contrast, the displacement efficiency of light oil components is higher and the transportation distance is longer. Intermolecular interaction has a remarkable effect on the displacement behavior of CO₂ in nanopores. On the other hand, it is discovered that a lower displacement rate is conducive to the miscible process of alkane and CO₂ and the overall displacement process of CO₂. The displacement efficiency drops significantly with the increase in displacement velocity. Nevertheless, once the displacement speed is extremely high, a strong driving force can facilitate the forward movement of alkane, and the displacement efficiency will recover slightly. Full article

Euphorbia uralensis belongs to the family Euphorbiaceae and is widely distributed in northern Xinjiang, making it a characteristic plant of the region in Xinjiang, China. The chemical composition and biological activity of Euphorbia uralensis have not yet been reported, although certain compounds isolated from Euphorbia plants in Xinjiang, China, have demonstrated exceptional multidrug resistance (MDR) reversal. This study aims to investigate the chemical components present in Euphorbia uralensis with the potential to reverse MDR. The aerial parts of Euphorbia uralensis were extracted using organic solvents of varying polarities, resulting in dichloromethane (Fr-E) and petroleum ether (Fr-S) fractions, which exhibited greater MDR reversal activity than the other fractions. The chemical constituents of the Fr-S fraction were analyzed using GC-MS. The chemical components of the Fr-E fraction were isolated and purified using column chromatography. The most effective compounds with MDR reversal activity were screened out, and the mechanism was investigated using molecular docking, molecular dynamics simulations, Western blotting, and rhodamine 123 staining. GC-MS analysis showed that the Fr-S fraction was rich in triterpenes, fatty acids, phenols, and long-chain alkanes, all of which were identified for the first time in Euphorbia uralensis. Among these, palmitic acid was present at a content level of 15.86%. This study notably unveils the discovery of a new compound and 16 previously recorded compounds for the first time in this plant, with the main types identified as steroids, sesquiterpenes, and flavonoids. The isolated compounds were tested for cytotoxicity and MDR reversal activity. The new compounds Euphouralosides A, pubinernoid A, naringenin, and punigratine showed good MDR reversal activity against MCF-7 and MCF-7/ADR cell lines. Punigratine was the most active compound. Moreover, punigratine could stably bind to the ABCB1 protein. Western blot analysis revealed that punigratine did not affect the expression of the ABCB1 protein in cells (p > 0.05). However, following treatment with punigratine (0.16 μM), there was a significant increase the intracellular accumulation of Rh123 in MCF-7/ADR cells (p < 0.05). These findings suggest that punigratine can inhibit the efflux of the ABCB1 protein, thereby overcoming MDR in tumors. This study provides a foundation for further research on the biological activity and medicinal potential of Euphorbia uralensis. Full article

Understanding lubrication at the nanoscale is essential for reducing friction. While alkanes, the primary component in most lubricants, have been studied for their molecular structure’s impact on rheology and behavior when confined by solid surfaces, the influence of confining surface texture remains underexplored. This research uses molecular dynamics simulations to investigate the rheological behavior of thin film lubrication between various patterned rough surfaces. The study focuses on sinusoidal, sawtooth, and squaretooth wave-patterned surfaces, using hexadecane as the lubricant. The simulations examine the effects under different normal loads and shear rates. Surface patterns significantly influence the formation and structure of crystalline bridges, depending on shear rates and normal loads. The sawtooth wave-patterned surface exhibits the highest viscosity under low normal load and shear rate conditions, forming crystalline bridges with a molecular orientation perpendicular to the shear direction. The squaretooth patterns exhibit the lowest viscosities due to the nematic order in crystalline bridges with molecules aligned in the shearing direction. The sinusoidal wave-patterned surface shows intermediary viscosity with disordered crystalline bridge groups formed with random molecular orientation. The lowest viscosity provided by the squaretooth pattern surface persists across various conditions, including both transitory and steady states, under high and low loads, and over a wide range of shear rates. However, the difference in shear viscosity is reduced at higher normal loads. This research provides valuable insights for designing nanoelectromechanical systems (NEMS) and other applications where boundary conditions are critical to lubrication. Full article