Search

Tannin-based foams have gained attention as a potential bio-based alternative to conventional synthetic foams. Traditionally, namely condensed tannins (CT) have been used, leaving the potential of hydrolysable tannins (HT) largely unexplored. This study compared the performance of chestnut (HT) and quebracho (CT) in tannin–protein-based foams at different tannin ratios. Using soy protein isolate (SPI) and hexamine under acidic conditions, a series of tannin foams were produced through a mechanical foaming method and analyzed for cell structure, compression strength, thermal conductivity, and chemical stability. Results show that chestnut tannin is viable in hexamine SPI formulations but is harder to process due to lower reactivity, further resulting in higher material densities compared to quebracho. Foams with higher quebracho content featured smaller, more interconnected cells, while increasing chestnut content led to larger, less interconnected cells. Compression strength decreased with higher chestnut content, while fire resistance and thermal conductivity were influenced by material density rather than tannin type. The 13C-NMR analysis revealed covalent bonding of hexamine with both tannins, but potential covalent bonds with SPI were undetectable. Overall, chestnut tannin can substitute quebracho tannin in hexamine-SPI foams, though with compromises in terms of specific material properties and processability. [ABSTRACT FROM AUTHOR]

ABSTRACT Besides classic illegal drugs, numerous designer drugs, also called new psychoactive substances (NPSs), are available on the global drug market. One of the biggest and fastest‐growing substance classes comprises the synthetic cannabinoids. According to the European Monitoring Centre for Drugs and Drug Addiction (EMCDDA), 254 out of 950 monitored substances belong to this group of NPS, with 9 new cannabinoids registered for the first time in 2023. For their purchase, it is not necessary to use the dark web. Due to the structural differences compared to the illegal Δ9‐THC (delta‐9‐tetrahydrocannabinol), the legal status changes and the synthetic cannabinoids are available via clear web pages. They come as powders or dissolved and sprayed onto non‐psychoactive layers such as cannabidiol hemp, industrial hemp or also on other plant material like herbal tea mixtures or dried flowers. These adulterated plant parts can be smoked as a substitute to the psychoactive and in many countries illegal Δ9‐THC‐containing hemp. The main task of this project was to check the identity of online available synthetic cannabinoid samples and to generate experimental data using a combination of gas and liquid chromatography with mass spectrometric detection and NMR‐based structure elucidation. In total, 25 substances in solid state were bought from various online shops. They turned out to be 21 synthetic cannabinoids after analysis, including 13 with no or incomplete experimental NMR data available in the literature and one, CH‐PIATA, which has not been mentioned in literature yet. More than 50% of the acquired substances were falsely declared. [ABSTRACT FROM AUTHOR]

ABSTRACT Alpinia zerumbet (Pers.) B.L.Burtt & R.M.Sm, known as shell ginger, is an aromatic plant widely distributed in tropical and subtropical regions. In Guizhou Province of China, its mature fruits have been used by the Miao people for the treatment of cardiovascular diseases. Although the bioactivities of mature fruits of A. zerumbet are derived from phytochemicals in the seeds and pericarps of the plant, there remains a dearth of reports on the isolation of phytochemicals from the pericarp of A. zerumbet. In the present study, the pericarps of mature fruits of A. zerumbet were extracted, and two new kavalactone dimers, alpingsin E (1) and aniba dimer D (2), were isolated. Their structures were determined on the basis of extensive spectroscopic analysis and NMR calculations. Especially, density functional theory–based NMR chemical shift calculations were employed to elucidate and confirm the relative configuration of 1 and 2. [ABSTRACT FROM AUTHOR]

Fine roots are key to ecosystem-scale nutrient, carbon (C), and water cycling, yet our understanding of fine root trait variation within and among tropical forests, one of Earth's most C-rich ecosystems, is limited. We characterized root biomass, morphology, nutrient content, and arbuscular mycorrhizal fungal (AMF) colonization to 1.2 m depths across four distinct lowland Panamanian forests, and related root characteristics to soil C stocks. We hypothesized that: (H1) Fine root characteristics vary consistently with depth across seasonal tropical forests, with deeper roots exhibiting more exploratory traits, such as for deep water acquisition; (H2) fine root characteristics vary among tropical forests mainly in surface soils, where resource availability also varies. We found consistent variation with depth across the four forests, including decreased root biomass, root tissue density, and AMF, and increased specific root length. Among the forests, there was variation in some fine root characteristics, including greater surface root biomass and lower SRL in the wettest forest, and smaller fine root diameter in the driest forest. We also found that root characteristics were related to total soil C stocks, which were positively related to root biomass and negatively related to specific root length. These results indicate emergent properties of root variation with depth across tropical forests, and show site-scale variation in surface root characteristics. Future work could explore the flexibility in root characteristics under changing conditions such as drought. [ABSTRACT FROM AUTHOR]

ABSTRACT One new monacolin analog, monacolin V (1), together with two new monacolin‐like natural products, 6‐hydroxyl monacolin P (2) and 3‐keto monacolin S (3), were isolated from the ethyl acetate portion of red yeast rice ethanol extract. Their structures were identified by HRESIMS and NMR experiments, and the complete assignments of 1H and 13C NMR data for three compounds were obtained by the aid of HSQC, HMBC, 1H‐1H COSY, and NOESY data. This is the first time that the NMR data of compounds 2 and 3 have been fully assigned. [ABSTRACT FROM AUTHOR]

A root factor for the accuracy of all quantum chemical calculations of nuclear magnetic resonance (NMR) chemical shifts is the quality of the molecular equilibrium geometry used. In turn, this quality depends largely on the basis set employed at the geometry optimization stage. This parameter represents the main subject of the present study, which is a continuation of our recent work, where new pecG-n (n = 1, 2) basis sets for the geometry optimization were introduced. A goal of this study was to compare the performance of our geometry-oriented pecG-n (n = 1, 2) basis sets against the other basis sets in massive calculations of 13C NMR shielding constants/chemical shifts in terms of their efficacy in reducing geometry factor errors. The testing was carried out with both large-sized biologically active natural products and medium-sized compounds with complicated electronic structures. The former were treated using the computation protocol based on the density functional theory (DFT) and considered in the theoretical benchmarking, while the latter were treated using the computational scheme based on the upper-hierarchy coupled cluster (CC) methods and were used in the practical benchmarking involving the comparison with experimental NMR data. Both the theoretical and practical analyses showed that the pecG-1 and pecG-2 basis sets resulted in substantially reduced geometry factor errors in the calculated 13C NMR chemical shifts/shielding constants compared to their commensurate analogs, with the pecG-2 basis set being the best of all the considered basis sets. [ABSTRACT FROM AUTHOR]

The control of metabolic networks is incompletely understood, even for glycolysis in highly studied model organisms. Direct real-time observations of metabolic pathways can be achieved in cellular systems with 13C NMR using dissolution Dynamic Nuclear Polarization (dDNP NMR). The method relies on a short-lived boost of NMR sensitivity using a redistribution of nuclear spin states to increase the alignment of the magnetic moments by more than four orders of magnitude. This temporary boost in sensitivity allows detection of metabolism with sub-second time resolution. Here, we hypothesized that dDNP NMR would be able to investigate molecular phenotypes that are not easily accessible with more conventional methods. The use of dDNP NMR allows real-time insight into carbohydrate metabolism in a Gram-positive bacterium (Lactoccocus lactis), and comparison to other bacterial, yeast and mammalian cells shows differences in the kinetic barriers of glycolysis across the kingdoms of life. Nevertheless, the accumulation of non-toxic precursors for biomass at kinetic barriers is found to be shared across the kingdoms of life. We further find that the visualization of glycolysis using dDNP NMR reveals kinetic characteristics in transgenic strains that are not evident when monitoring the overall glycolytic rate only. Finally, dDNP NMR reveals that resting Lactococcus lactis cells use the influx of carbohydrate substrate to produce acetoin rather than lactate during the start of glycolysis. This metabolic regime can be emulated using suitably designed substrate mixtures to enhance the formation of the C4 product acetoin more than 400-fold. Overall, we find that dDNP NMR provides analytical capabilities that may help to clarify the intertwined mechanistic determinants of metabolism and the optimal usage of biotechnologically important bacteria. [ABSTRACT FROM AUTHOR]

The characteristics of biochar vary widely depending on the type of biomass and thermochemical conversion method. In this study, four types of biomass (kenaf, rice husk, corncob, and wood chips) were subjected to hydrothermal carbonization and torrefaction at 220 °C, 260 °C, and 300 °C for 30 min. The acquired biochars showed significant differences in the type of reaction and biomass. At each temperature, the decomposition of volatiles was more severe in hydrochar (HC) than in torrefied char (TC). The mass yields of HC were 44.30–61.63 wt.% (220 °C), 20.89–37.04 wt.% (260 °C), and 12.59–29.19 wt.% (300 °C), whereas the mass yields of TC were 94.73–97.69 wt.% (220 °C), 87.19–95.04 wt.% (260 °C), and 68.22–80.78 wt.% (300 °C). The elemental and thermal characteristics of TC changed gradually as the reaction temperature increased, and the characteristics of HC were enhanced rapidly. Wood chip biochar that was reacted at 300 °C showed the highest heating values of 28.77 MJ/kg (HC) and 21.09 MJ/kg (TC). The results of chemical analyses showed that hydrothermal carbonization strongly affected the cleavage of inter- and intra-molecular carbon bonds in cellulose and hemicellulose. In contrast, torrefaction removed the thermally fragile moisture and hemicellulose content from biomass. [ABSTRACT FROM AUTHOR]

Isatin-derived Schiff bases are the subject of many studies, finding wide application areas in polymer technology, pharmaceutical industry, and medicine. In this study, a series of new Schiff bases were prepared from monothiocarbohydrazones based on isatins with different substituents (5-F, 5-Br, 5-I, and 5-MeO). The chemical structures of the synthesized compounds were determined using 1H NMR, 13C NMR, FTIR spectroscopic techniques, and elemental analysis. Antioxidant activity determinations of 23 compounds were performed using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical quenching method. The highest percent inhibition value at 10 µM concentration was shown by compound number 22, 5-bromoisatin Schiff base containing 3-methoxy-4-hydroxy group. Compound 17, a 5-iodoisatin Schiff base containing 3-methoxy-4-hydroxy group, showed the highest antioxidant activity with an IC50 value of 9.76 ± 0.03 µM. In addition to the theoretical analysis of the compounds, both their spectroscopic and antioxidant properties were investigated. The ground-state geometries and some chemical reactivity parameters of the compounds were calculated using the B3LYP/6-311 + + G(2d,2p) approach. Besides intramolecular interactions, substituent effects, and some QTAIM parameters, the calculations were also performed to study the electronic properties of reactive N/O–H bonds and were used to interpret the experimental results. The effects of the electronic parameters and intramolecular interactions of reactive N/O–H bonds on the antioxidant properties of the compounds were investigated. Additionally, the relationships of DPPH reactions with delocalization indices of N/O-H bonds and the pattern of SET/HAT mechanisms with electronic variables were analyzed. Examination of electron and hydrogen atom transfer mechanisms has shown the dominance of electron transfer, supported by the correlation coefficients between IC50 values and SET reaction energies. [ABSTRACT FROM AUTHOR]

The bio-depolymerization of coal is a promising technology for converting coal into low-molecular-weight industrial chemicals. In this study, we investigated the characteristics of biodepolymerized coal (BDC) and the associated depolymerization pathway. We analyzed the extracellular enzyme activities of Hypocrea lixii AH in the biodepolymerization system, performed Fourier transform infrared spectroscopy (FTIR) and 13C nuclear magnetic resonance spectroscopy (NMR) of BDC, and performed gas chromatography and mass spectrometry (GC/MS) of the BDC methanol extract. Results showed that the activities of peroxidase (POD), polyphenol oxidase (PPO), laccase (Lac), and lignin peroxidase (LiP) were 1377, 162, 10, and 1.919 U, respectively. Following biodepolymerization by Hypocrea lixii AH, 20 organic compounds were identified. Benzaldehyde 4-hydroxy-3,5-dimethoxy was the most dominant at 33.16%, followed by (Z)-9-octadecenamide, accounting for 14.73%. The aromaticity (fa) decreased from 54.3% to 23.7%, suggesting ring-opening reactions catalyzed by LiP and Lac. The ratio of carbonyl carbon (faC) increased from 8.3% to 16.2%, suggesting oxidation reactions catalyzed by POD. By comparing the structure of the Fushun oxidized coal model and BDC, a biodepolymerization pathway was elucidated. Biodepolymerization of Fushun oxidized coal is an oxidation–depolymerization process catalyzed by a series of enzymes, which breaks the aromatic rings and oxidizes side chains. Altogether, our findings provide a theoretical support for the chemical application of BDC. [ABSTRACT FROM AUTHOR]

Early NMR studies of several heterohelicenes containing an annular nitrogen atom and a thiophene ring in their structure suggested the possibility of the lengthening of the carbon–carbon bonds in the interior of the helical turn of the molecule based on the progressive upfield shift of 13C resonances toward the center of the helical turn. We now report a comprehensive analysis of the optimized geometry and a comparison of the calculated vs. observed 1H and 13C NMR chemical shifts of nineteen representative benzothienoquinoline heterohelicenes. As was initially hypothesized on the basis of the progressive upfield shift of carbon resonances toward the center of the interior helical turn, the present computational study has demonstrated that carbon–carbon bonds indeed have more sp3 character and are longer than normal sp2 bonds to accommodate the helical twist of the molecule, as expected. [ABSTRACT FROM AUTHOR]

Mefloquine (MQ) is an antimalarial medication prescribed to treat or malaria prevention.. When taken by children, vomiting usually occurs, and new doses of medication frequently need to be taken. So, developing pediatric medicines using taste-masked antimalarial drug complexes is mandatory for the success of mefloquine administration. The hypothesis that binding mefloquine to an ion-exchange resin (R) could circumvent the drug's bitter taste problem was proposed, and solid-state 13C cross-polarization magic angle spinning (CPMAS) NMR was able to follow MQ–R mixtures through chemical shift and relaxation measurements. The nature of MQ–R complex formation could then be determined. Impedimetric electronic tongue equipment also verified the resinate taste-masking efficiency in vitro. Variations in chemical shifts and structure dynamics measured by proton relaxation properties (e.g., T1ρH) were used as probes to follow the extension of mixing and specific interactions that would be present in MQ–R. A significant decrease in T1ρH values was observed for MQ carbons in MQ–R complexes, compared to the ones in MQ (from 100–200 ms in MQ to 20–50 ms in an MQ–R complex). The results evidenced that the cationic resin interacts strongly with mefloquine molecules in the formulation of a 1:1 ratio complex. Thus, 13C CPMAS NMR allowed the confirmation of the presence of a binding between mefloquine and polacrilin in the MQ–R formulation studied. [ABSTRACT FROM AUTHOR]

Chitin, a ubiquitous biopolymer, holds paramount scientific and economic significance. Historically, it has been primarily isolated from marine crustaceans. However, the surge in demand for chitin and the burgeoning interest in biopolymers have necessitated the exploration of alternative sources. Among these methods, the mulberry silkworm (Bombyx mori) has emerged as a particularly intriguing prospect. To isolate chitin from Bombyx mori, a chemical extraction methodology was employed. This process involved a series of meticulously orchestrated steps, including Folch extraction, demineralization, deproteinization, and decolorization. The resultant chitin was subjected to comprehensive analysis utilizing techniques such as attenuated total reflectance–Fourier transform infrared spectroscopy (ATR-FTIR), 13C nuclear magnetic resonance (NMR) spectroscopy, and wide-angle X-ray scattering (WAXS). The obtained results allow us to conclude that the Bombyx mori represents an attractive alternative source of α-chitin. [ABSTRACT FROM AUTHOR]

Nickel complexes with a two‐electron reduced CO2 ligand (CO22−, "carbonite") are investigated with regard to the influence alkali metal (AM) ions have as Lewis acids on the activation of the CO2 entity. For this purpose complexes with NiII(CO2)AM (AM=Li, Na, K) moieties were accessed via deprotonation of nickel‐formate compounds with (AM)N(iPr)2. It was found that not only the nature of the AM ions in vicinity to CO2 affect the activation, but also the number and the ligation of a given AM. To this end the effects of added (AM)N(R)2, THF, open and closed polyethers as well as cryptands were systematically studied. In 14 cases the products were characterized by X‐ray diffraction and correlations with the situation in solution were made. The more the AM ions get detached from the carbonite ligand, the lower is the degree of aggregation. At the same time the extent of CO2 activation is decreased as indicated by the structural and spectroscopic analysis and reactivity studies. Accompanying DFT studies showed that the coordinating AM Lewis acidic fragment withdraws only a small amount of charge from the carbonite moiety, but it also affects the internal charge equilibration between the LtBuNi and carbonite moieties. [ABSTRACT FROM AUTHOR]

The object of the study is lignite. Analytical testing techniques, such as elemental analysis, 13C nuclear magnetic resonance (13C NMR) spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and high-resolution transmission electron microscopy (HRTEM), were used to acquire information on the structural parameters of lignite. The aromaticity of Xianfeng lignite is 43.57%, and the aromatic carbon structure is mainly naphthalene and anthracene/phenanthrene. The aliphatic carbon structure is dominated by cycloalkanes, alkyl side chains, and hydrogenated aromatics. Oxygen is mainly present in ether oxygen, carboxyl, and carbonyl groups. Nitrogen is mainly in the form of pyrrole nitrogen and quaternary nitrogen. Sulfur is mainly thiophene sulfur. According to the analysis results, the molecular structure model of XF lignite was constructed. The molecular formula is C184H172O39N6S2. The 2D structure was converted to a 3D structure using computer simulation software and optimized. The optimized model has a remarkable stereoconfiguration, and the aromatic lamellae are irregularly arranged in space. The aromatic rings were mainly connected by methylene, hypomethylene, methoxy, and aliphatic rings. In addition, the simulated 13C NMR spectra are in good agreement with the experimental spectra. This shows the rationality of the 3D chemical structure model. [ABSTRACT FROM AUTHOR]

NMR spectroscopy has become a standard technique in studies both on carbon capture and storage. 13C NMR allows the detection of two peaks for carbonated aqueous samples: one for CO2(aq) and another one for the species H2CO3, HCO3−, and CO32−—herein collectively named HxCO3x‐2. The chemical shift of this second peak depends on the molar fraction of the three species in equilibrium and has been used to assess the equilibrium between HCO3− and CO32−. The detection of H2CO3 at low pH solutions is hindered, because of the concurrent liberation of CO2 when the medium is acidified. Herein, a valved NMR tube facilitates the detection of the HxCO3x‐2 peak across a wide pH range, even at pH 1.8 where the dominant species is H2CO3. The method employed the formation of frozen layers of NaH13CO3 and acid solutions within the tube, which are mixed as the tube reaches room temperature. At this point, the tube is already securely sealed, preventing any loss of CO2 to the atmosphere. A spectrophotometry approach allowed the measurement of the actual pH inside the pressurized NMR tube. The chemical shift for H2CO3 was determined as 160.33 ± 0.03 ppm, which is in good agreement with value obtained by DFT calculations combined with Car–Parrinello molecular dynamics. The H2CO3 pKa value determined by the present method was 3.41 ± 0.03, for 15% D2O aqueous medium and 0.8 mol/L ionic strength. The proposed method can be extended to studies about analogs such as alkyl carbonic and carbamic acids. [ABSTRACT FROM AUTHOR]

Plant‐ and microbially derived carbon (C) are the two major sources of soil organic matter (SOM), and their ratio impacts SOM composition, accumulation, stability, and turnover. The contributions of and the key factors defining the plant and microbial C in SOM along the soil profile are not well known. By leveraging nuclear magnetic resonance spectroscopy and biomarker analysis, we analyzed the plant and microbial C in three soil types using regional‐scale sampling and combined these results with a meta‐analysis. Topsoil (0–40 cm) was rich in carbohydrates and lignin (38%–50%), whereas subsoil (40–100 cm) contained more proteins and lipids (26%–60%). The proportion of plant C increases, while microbial C decreases with SOM content. The decrease rate of the ratio of the microbially derived C to plant‐derived C (CM:P) with SOM content was 23%–30% faster in the topsoil than in the subsoil in the regional study and meta‐analysis. The topsoil had high potential to stabilize plant‐derived C through intensive microbial transformations and microbial necromass formation. Plant C input and mean annual soil temperature were the main factors defining CM:P in topsoil, whereas the fungi‐to‐bacteria ratio and clay content were the main factors influencing subsoil CM:P. Combining a regional study and meta‐analysis, we highlighted the contribution of plant litter to microbial necromass to organic matter up to 1‐m soil depth and elucidated the main factors regulating their long‐term preservation. [ABSTRACT FROM AUTHOR]

Cesium lead bromide perovskite (CsPbBr3) nanocrystals have raised impressive interest as efficient and stable optoelectronic materials. Size and morphology play important roles in the final performances of these materials and advanced characterization studies are needed to elucidate structural and surface properties. In this work, CsPbBr3 cubic nanocrystals were obtained by colloidal synthesis and characterized by multinuclear Solid State NMR (SSNMR), complemented by X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM) and optical spectroscopy. The multinuclear NMR approach allowed the different components of the nanocubes to be separately observed. In particular, the surface ligands and their interactions with the nanocubes surface were investigated by 1H and 13C NMR experiments, while the structural investigation of the perovskite nanocubes was addressed by exploiting 207Pb and 133Cs spectral properties in comparison with bulk CsPbBr3. Static 207Pb NMR spectra indicated a possible contribution of chemical shift anisotropy from the 207Pb nuclei of the outer layer. The 133Cs NMR spectra showed signals with different chemical shifts for cesium atoms in at least three regions of the nanocubes, from the inner core to the surface, which were interpreted in terms of cubic layers with different distances from the surface using a simple geometrical model. This interpretation was also supported by 133Cs longitudinal relaxation time measurements. [ABSTRACT FROM AUTHOR]

Structurally simple two rod-like mesogens with a three-ring core consisting of biphenyl and phenyl rings are synthesised to investigate the mesophase properties, molecular organisation and the orientational order parameter. In mesogen-1, a dodecyloxy terminal chain is present on the biphenyl ring while the phenyl ring is free from substituent. For mesogen-2, in addition to the dodecyloxy chain, the butyl chain is placed on the phenyl ring. The Hot-stage optical polarising microscopy (HOPM) and differential scanning calorimetry (DSC) measurements show smectic A (SmA), smectic B (SmB), and crystal E (CryE) phases for mesogen-1 and SmA, smectic C (SmC) and smectic F (SmF) phases for mesogen-2. The presence of smectic mesophases is established by X-ray Diffraction (XRD). 1D and 2D 13C solid-state NMR experiments are performed in smectic mesophases to find the orientational order parameters of the phenyl rings of the core. The main order parameter (Szz) of the mesogens in the SmB and SmF phase is in the range of 0.87–0.93. The excellent spectral resolution noticed in 13C NMR spectra in the SmB mesophase (mesogen-1) indicates that the internal rotations of the molecules along the long axis are primarily unhindered. [ABSTRACT FROM AUTHOR]

The basis set issue has always been one of the most important factors of accuracy in the quantum chemical calculations of NMR chemical shifts. In a previous paper, we developed new pecS-n (n = 1, 2) basis sets purposed for the calculations of the NMR chemical shifts of the nuclei of the most popular NMR-active isotopes of 1–2 row elements and successfully approbated these on the DFT calculations of chemical shifts in a limited series of small molecules. In this paper, we demonstrate the performance of the pecS-n (n = 1, 2) basis sets on the calculations of as much as 713 1H and 767 13C chemical shifts of 23 biologically active natural products with complicated stereochemical structures, carried out using the GIAO-DFT(PBE0) approach. We also proposed new alternative contraction schemes for our basis sets characterized by less contraction depth of the p-shell. New contraction coefficients have been optimized with the property-energy consistent (PEC) method. The accuracies of the pecS-n (n = 1, 2) basis sets of both the original and newly contracted forms were assessed on massive benchmark calculations of proton and carbon chemical shifts of a vast variety of natural products. It was found that less contracted pecS-n (n = 1, 2) basis sets provide no noticeable improvement in accuracy. These calculations represent the most austere test of our basis sets as applied to routine calculations of the NMR chemical shifts of real-life compounds. [ABSTRACT FROM AUTHOR]

Composting is described as a sustainable alternative to organic waste reuse from the agricultural and household sectors. The organic matter degradation and stabilization product presents great variability due to the waste composition used. Thus, the use of techniques that allow the monitoring of the decomposition process is necessary to determine the quality of the final product. Therefore, this review critically analyzes and updates the chemical spectroscopy methods described for the evaluation of the organic matter transformation in the composting process to optimize and generate amendments for agricultural use. This review examines spectroscopic techniques such as ultraviolet-visible (UV-Vis), infrared (IR), fluorescence, and 13C NMR reported for the evolution and maturation of carbonate structures in composting. In addition, they are used in the study of indicators for monitoring the degradation of complex structures, such as sugars and proteins, for the formation of precursors that are responsible for the formation of highly stabilized substances such as humic and fulvic compounds. Finally, these parameters may be used to elucidate organic matter degradation and its stabilization process, establish patterns that characterize each stage of composting along with its physicochemical characteristics, and monitor potential phytotoxicity levels. [ABSTRACT FROM AUTHOR]

In the nuclear magnetic resonance (NMR) test of coal, when the spinning frequency of magic‐angle spinning (MAS) is less than the frequency range of chemical shift anisotropy, serious aromatic carbon spinning sidebands will appear. Existing solutions to the sideband effect, such as changing the MAS frequency, inserting total suppression of sidebands (TOSS) pulse sequences, or simply defining the peak after chemical shift of 200 ppm as the sideband peaks generated by aromatic carbon peak, multipling the identified sideband integral by 2 and adding to the main peaks of protonated aromatic carbon and aromatic bridgehead carbon. None of these methods can reasonably correct for the sideband effect and cause errors to accurately quantifying the carbon structure parameters. Compared with 13C nuclear magnetic resonance (13C NMR) spectrum without sideband suppression (13C CP‐MAS NMR) and 13C NMR spectrum under sideband suppression conditions (13C CP‐MAS/TOSS NMR), according to the chemical shifts of the main peaks of four aromatic carbons, namely protonated aromatic carbon, aromatic bridgehead carbon, alkylated aromatic carbon and oxygen‐linked aromatic carbon, combined with the MAS frequency, the first‐ and second‐level sideband peaks generated by four types of aromatic carbons were accurately located and quantified, and they were added to the corresponding aromatic carbon main peaks in 13C CP‐MAS/TOSS NMR spectrum, thus realizing the accurate correction of sideband effect of the solid‐state 13C NMR spectrum of coal samples. The relative area of corrected aliphatic carbon, carbonyl (carboxyl) carbon, and various aromatic carbons were recalculated, and more accurate carbon structure parameters were obtained, which is significant for studying the coal structure from a microscopic perspective. [ABSTRACT FROM AUTHOR]

A series of chlorophenyl thiazolyl naphthyl methanone derivatives have been synthesized and found to possess a wide spectrum of biological activities. Chlorophenyl thiazolyl naphthyl methanone has been synthesized and characterized by elemental analysis IR, ¹H and 13C NMR and mass spectral data. Quantum chemical computation and vibrational spectral analysis of chlorophenyl thiazolyl naphthyl methanone have been carried out using DFT level B3LYP with 6-31G basis set. Electric dipole moment (µ) values have been computed by utilizing ab initio and DFT quantum mechanical calculations. The energy gap is an indicator of chemical reactivity, kinetic stability and polarizability. The novel compounds show very good antioxidant and anticancer activity. Docking studies have been performed for target molecules using the molecular docking software. The antioxidant activity of chlorophenylthiazolylnaphthylmethanone has been analyzed using the DPPH radical scavenging assay. Among the studied compounds, (4-chlorophenyl-2-diethylaminothiazol-5-yl-2-naphthyl)methanone 2b is highly active on the SKMEL cell line. [ABSTRACT FROM AUTHOR]

Early NMR studies of several heterohelicenes containing an annular nitrogen atom and a thiophene ring in their structure suggested the possibility of the lengthening of the carbon–carbon bonds in the interior of the helical turn of the molecule based on the progressive more shielded nature of 13C resonances toward the center of the helical turn. Computational chemistry capabilities when those NMR studies were performed were primitive in comparison to what is now possible. We now report the optimized geometry and a comparison of the calculated versus observed 1H and 13C NMR chemical shift assignments for [1]benzothieno[2,3‐c]naphtho[1,2‐f]quinoline that confirms these suspicions. [ABSTRACT FROM AUTHOR]

Substituted acrylamides have found an extensive application in organic and medical chemistry; therefore, it is very important to get insight into their features such as electronic structure, spectral properties, and stereochemical transformations. A correct interpretation of the chemical behavior and biological activity of these heteroatomic systems is impossible without knowledge of the structure of stereodynamic forms and factors determining their relative stability. The structure and peculiarities of stereodynamic behavior of substituted acrylamides and their model compounds were studied by dynamic and multinuclear 1H, 13C, and 15N nuclear magnetic resonance (NMR) spectroscopy in CDCl3 and DMSO‐d6 solution. It has been established that acrylamides in solution are realized as Z‐ and E‐isomers, with the E‐rotamer being somewhat predominant. The obtained experimental values of the free activation energy of rotamers vary within 15–17 kcal/mol, depending on the stereochemical structure of the molecule. 15N NMR spectroscopy is the most reliable and fastest method for determining the structural and stereochemical features of nitrogen‐containing compounds. [ABSTRACT FROM AUTHOR]

This study examines the influence of mefenamic acid on the physical and chemical properties of silica aerogels, as well as its effect on the sorption characteristics of the composite material. Solid state magic angle spinning nuclear magnetic resonance (MAS NMR) and high-pressure 13C NMR kinetic studies were conducted to identify the presence of mefenamic acid and measure the kinetic rates of CO2 sorption. Additionally, a high-pressure T1–T2 relaxation-relaxation correlation spectroscopy (RRCOSY) study was conducted to estimate the relative amount of mefenamic acid in the aerogel's pores, and a high-pressure nuclear Overhauser effect spectoscopy (NOESY) study was conducted to investigate the conformational preference of mefenamic acid released from the aerogel. The results indicate that mefenamic acid is affected by the chemical environment of the aerogel, altering the ratio of mefenamic acid conformers from 75% to 25% in its absence to 22% to 78% in the presence of aerogel. [ABSTRACT FROM AUTHOR]

• Interactive effects of multi-climate change drivers on decomposition were studied. • Warming inhibited litter decomposition in the early stage (1–2 years) and promoted it in the later stage (3–4 years). • Increased precipitation significantly accelerated litter decomposition initially, but not in the later stages. • Temporal variations in temperature sensitivity were impacted by soil moisture and N addition. Climate warming, precipitation changes, and reactive nitrogen (N) input are important environmental changes that can critically affect litter decomposition and soil carbon (C) dynamics. However, it remains unclear whether and how their effects and/or relative contribution vary across different decomposition stages. We assessed the effects of warming, precipitation changes and N addition, alone and in combination, on litter loss at various stages of the decomposition process in a semi-arid grassland. We found that warming inhibited litter decomposition in the early stage (1–2 years) and promoted it in the later stage (3–4 years). The temperature sensitivity of decomposition was affected by both soil moisture and N addition. Increased precipitation significantly accelerated litter decomposition initially, but not in the later stages. In the litter-soil incubation experiment, we observed that high-quality litter, characterized by low carbohydrate C:methoxyl C (CC:MC) ratio and/or CN ratios, displayed greater sensitivity to changes in moisture. In comparison, low-quality litter exhibits high temperature sensitivity of microbial respiration. Overall, our findings show that the climate sensitivity of litter decomposition exhibited distinct temporal dynamics, with increasing warming sensitivity of decomposition and decreasing moisture sensitivity of decomposition over time. Given that many current decomposition models use a constant sensitivity parameter (e.g., Q 10 value = 2.0) throughout the decay process, our results suggest that incorporation of such temporal dynamics into decomposition models may enhance their predictive power. [ABSTRACT FROM AUTHOR]

The stability and chemical composition of SOM are related to the changes of the proportions of old and young SOM. However, there are few studies that investigated the effects of no-tillage (NT) on the stability, chemical composition, and sources of SOM. In this study, the effects of 9-years of NT on the contents of total, thermally labile and stable SOM, their chemical composition and the contributions from C 3 and C 4 plants were determined. Before application of NT, the field has been used for C 4 maize cultivation under conventional tillage (CT) management about 80 years after initial C 3 grassland reclamation. Soil samples were collected in the 0–20 cm soil profile. Under NT treatment, the contents of total SOC, thermally labile and stable SOC, and C 4 -SOC decreased with soil depths. However, they were greater in the 0–10 cm layers than that in the 10–20 cm layer under CT. The contents of C 3 -SOC showed no change with depths under both of tillage treatments. NT had greater contents of total SOC, C 4 -SOC, thermal-labile SOC, and C 4 -SOC thermal-labile than CT in the 0–5 cm layer, but lower in the subsoil layers. The contents of C 3 -SOC thermal-labile decreased in the 0–5 cm layer under NT. The alkyl-C and O-alkyl-C were the main fractions of thermal-labile SOM and aromatic-C was the dominant fraction of thermal-stable SOM. C 4 -SOC (young SOC) was significantly positively correlated with alkyl-C and O-alkyl-C and negatively correlated with aromatic-C. Our results indicated that: (1) compared with continuously CT, applying NT resulted in SOC accumulation in the surface layer, (2) more maize residue input increased the new thermally labile and stable SOM yet lead to decrease the C 3 -SOC thermal-labile under NT, (3) the contributions of C 3 and C 4 -direved SOM determined the chemical compositions of various SOM pools. • The C 4 -SOC was greater under NT than CT in the 0–5 cm, but lower in 5–20 cm layer. • No-tillage accelerates the decomposition of thermal-labile SOC derived from old C 3 plant. • Alkyl-C and O-alkyl-C are thermal-labile and aromatic-C is thermal-stable. [ABSTRACT FROM AUTHOR]

Condensed tannin copolymerized with hyperbranched tris(2-aminoethyl)amine-urea formed by amine-amido deamination yields a particleboard thermosetting adhesive without any aldehydes satisfying the requirements of relevant standards for the particleboard internal bond strength. The tannin–triamine–urea cures well at 180 °C, a relatively low temperature for today's particleboard hot pressing. As aldehydes were not used, the formaldehyde emission was found to be zero, not even in traces due to the heating of wood. The effect is ascribed to the presence of many reactive sites, such as amide, amino, and phenolic groups belonging to the three reagents used. The tannin appears to function as an additional cross-linking agent, almost a nucleating agent, for the triamine–urea hyperbranched oligomers. Chemical analysis by MALDI ToF and 13C NMR has shown that the predominant cross-linking reaction is that of the substitution of the tannin phenolic hydroxyls by the amino groups of the triamine. The reaction of tannin with the still-free amide groups of urea is rather rare, but it may occur with the rarer tannin flavonoid units in which the heterocyclic ring is opened. Due to the temperature gradient between the surfaces and the board core in the particleboard during hot pressing, the type and the relative balance of covalent and ionic bonds in the resin structure may differ in the surfaces and the board core. [ABSTRACT FROM AUTHOR]

Synthesis and characterization of a new β-octa-substituted zinc phthalocyanine complex from the [ZnPc(CO2H)8] complex are reported in this work. Compound of general formula C64H36N12O12S4Zn with good purity is obtained and confirmed by elemental analysis. The vibrational spectrometry spectra (IR and Raman) attest not only the characteristic vibration bands of phthalocyanines, but also those of functional groups located at the complex periphery. In X-ray photoelectron spectrometry (XPS), the values of the binding energies prove the presence of the sulfur of R-SH groups; which confirms the presence of the S-H bond in the reaction compound. Solid-state 13C Nuclear Magnetic Resonance Spectroscopy (13C NMR) makes possible establishment of a good correlation between the various carbons and the proposed structure. [ABSTRACT FROM AUTHOR]

The controversial question of whether optical rotation data can be used to distinguish floral from honeydew honey was investigated. Specific optical rotation angles were determined for 41 honey samples, including floral, honeydew, and adulterated honey, indicating that moderate to high positive optical rotation angles were found for all adulterated samples measured. A strong correlation between the sugar profile and the specific optical rotation angle of honey was confirmed, and a method based on 13C NMR metabolomics was proposed to calculate specific optical rotation angles with good correlation with the experimental values. The results indicate that optical rotation is not a reliable method for distinguishing the origin of honey but could indicate adulteration. [ABSTRACT FROM AUTHOR]

Codeine N‐oxide 2 is an active metabolite of codeine obtained by oxidation and observed as a degradant in codeine drug products such as syrups. Oxidation of codeine's N‐methyl function can deliver two regio‐isomers due to chirality of the tetra‐substituted nitrogen. Hydrogen peroxide oxidation of codeine was performed and induced two different isomers in a 9:1 ratio; these isomers were isolated using preparative high performance liquid chromatography (HPLC) and fully characterized by nuclear magnetic resonance (NMR) techniques. We describe the complete assignment of the minor isomer of codeine N‐oxide 3 and attribute a (S) configuration (N‐methyl axial) of the tetra‐substituted nitrogen. The effects of N‐oxidation on the 15N chemical shifts of the codeine are presented. The 15N shifts were determined using the CIGAR‐HMBC experiment at natural abundance, and the nitrogen resonance of codeine shifted downfield from 42.8 to 118.7 ppm for both N‐oxide isomers. [ABSTRACT FROM AUTHOR]

Purpose: Winter snow cover is a key control over soil biogeochemical cycles in cold biomes but has decreased with climate warming, particularly in high-latitude and high-altitude areas. Previous studies have found a decline in carbon (C) release from decomposing litter without snow cover, yet partitioning what C fractions respond to snow removal remains not fully understood. Methods: Here we incubated fir and birch litter in microcosms over two years of decomposition in an alpine forest to assess the release of various C fractions with and without snow cover using 13C nuclear magnetic resonance (NMR). Results: We found that 51% and 61% of total organic C was lost from fir and birch litter, respectively, after two years of decomposition, and 59% and 60% of this C was decomposed during winter. More C was lost from both fir and birch litter under snow cover, and the decomposition rate of birch litter C was decreased by 50% after snow removal. However, only O-alkyl C (particularly carbohydrate C) release was reduced with snow removal, and the release of other C fractions (i.e., alkyl C, aromatic C and carbonyl C) did not change significantly after removing snow cover. Delayed O-alkyl C release from fir and birch litter was in accordance with the declines in soil dissolved organic C and microbial respiration rate under removed snow plots, but this delay induced by snow removal did not carry over to the following growing season. Conclusion: We conclude that a reduction in winter snow cover regulates early decomposition of plant litter by controlling the rapid release of more labile C fractions (i.e., carbohydrates) in seasonally snow-covered ecosystems. [ABSTRACT FROM AUTHOR]

4-Benzyl-4-hydroxypiperidines 1-8 have been synthesized through Mannich reaction and were characterized through high resolution ¹H and 13C NMR spectra in CDCl3. The conformational studies of the above eight compounds have been thoroughly done by using proton and 13C spectral data and the assigned conformations were also supported by Hybrid HF/DFT B3LYP/6-3G* calculations. These results are published earlier by us. In order to study the effect of solvent on the chemical shifts of these piperidines, ¹H NMR spectra were recorded in C6D6 and DMSO-d6. The effect of change of solvents results appreciable change in the chemical shifts of various protons in the title compounds. [ABSTRACT FROM AUTHOR]

Benzimidazole is an important heterocyclic fragment, present in many biologically active compounds with a great variety of therapeutic purposes. Most of the benzimidazole activities are explained through the existence of 1,3-tautomeric equilibrium. As the binding affinity of each tautomer to a protein target depends on an established bioactive conformation, the effect of tautomers on the ligand protein binding mechanism is determinant. In this work, we searched and analyzed a series of reported 13C-NMR spectra of benzazoles and benzazolidine-2-thiones with the purpose of estimating their tautomeric equilibrium. Herein, several approaches to determine this problem are presented, which makes it a good initial introduction to the non-expert reader. This chemical shift difference and C4/C7 signals of benzimidazolidine-2-thione and 1-methyl-2-thiomethylbenzimidazole as references were used in this work to quantitatively calculate, in solution, the pyrrole–pyridine tautomeric ratio in equilibrium. The analysis will help researchers to correctly assign the chemical shifts of benzimidazoles and to calculate their intracyclic or exocyclic tautomeric ratio as well as mesomeric proportion in benzimidazoles. [ABSTRACT FROM AUTHOR]

Identification of insecticidal compounds from the entomopathogenic fungus Metarhizium anisopliae crude extract was performed by TLC and column fractionation. From the fractionation four fractions were separated and tested for larvicidal, pupicidal and adulticidal potential against Aedes aegypti, Anopheles stephensi and Culex quinquefasciatus mosquitoes. Among the four fractions the fraction-3 was most effective against larvae with LC50 values, 1.238, 1.300 and 2.899 for pupae, 1.440, 1.657, 2.593 and adult, 1.988, 2.037 and 4.086 µg/ml against Ae. aegypti, An. stephensi and Cx. quinquefasciatus at 24 h post treatment respectively. The effective fraction-3 were charectrized through FT-IR, UV–Vis spectroscopy, 13C-NMR and 1H-NMR, HPLC, and LC–MS analysis allowed to identifying the effective compound in fraction-3. Overall, the results confirmed the use of the fungus derived molecules as an active green pesticide against mosquito vectors of public importance and led to the identification of highly effective mosquitocidal products. In particular the toxic activity of aucubin far encompassed that of the large majority of earlier studied microbial insecticides, making this molecule an ideal candidate for the development of insecticides in the "real world". [ABSTRACT FROM AUTHOR]

The structural characteristics of soil organic matter (SOM) play an important role in improving soil organic carbon (SOC) sequestration capacity and maintaining soil fertility levels. This study selected saline - alkaline abandoned farmland as a control (0a), and cotton fields were continuously planted for 5, 10, 15, 20 and 25 years after reclamation. The results showed that the lowest soil electrical conductivity and total nitrogen are found in 0a, the highest pH (5a) and Available potassium content are found in 0a. SOC and humus contents were significantly increased by reclamation, which showed a trend of first increase and then decrease, and the highest value was observed in continuous cropping cotton 10a. In addition, the SOM is basically aliphatic. When the cotton field was continuously planted for 15a. Alkyl C: O-alkyl C and hydrophobicity index were the highest, indicating that the alkylation degree of SOM was high, the decomposition ability was strong, and the stability was improved. These results provide guidance for our study of SOM in different cotton continuous cropping systems and will provide insights into the dynamics pathways of humus substances stabilisation in northwest China. [ABSTRACT FROM AUTHOR]

• The microcrystalline structure of semi-coke was analyzed. • The calculated aromatic carbon ratios of XRD, FTIR and 13C NMR were compared. • The lattice fringes with sizes of below 3 × 3 have high proportion. • A chemical and structural properties of structure met the experimental data. To efficiently utilize semi-coke as a carbon-based material, the molecular dimension characteristics and structure of semi-coke were studied based on XRD, XPS, FTIR, 13C NMR, and HRTEM in this paper. The XRD results show that the semi-coke has fewer side chain functional groups, and the aromatic carbon rate (f a) can be calculated to be 82.33 %. FTIR results show that the content of CH 2 in semi-coke is higher than that of CH 3 , indicating that the side chain functional groups of char are less, which is consistent with the XRD results. At the same time, the aromatic carbon rate calculated by FTIR was 95.41 %. The occurrence forms of C, N, and O were analyzed by XPS, in which C mainly existed in the form of C C/C H, O mainly existed in the form of -C-O, and N mainly existed in the form of pyridine and pyrrole. The 13C NMR fitting results show that the carbon in the semi-coke mainly exists in the form of aromatic carbon and the aromatic carbon rate is 93.32 %. In addition, the ratio of aromatic bridgehead carbon to peri carbon (X BP) is 0.472. HRTEM results show that the lattice fringes in semi-coke are mainly composed of 1 × 1, 2 × 2, and 3 × 3. Finally, the model parameters are consistent with the experimental results, which provides a molecular theoretical basis for further study of semi-coke. [Display omitted] [ABSTRACT FROM AUTHOR]

Hordeum vulgare husk, a cereal grain, is rich in dietary fiber and prebiotics beneficial for the gut microbiota and host organism. This study in v estigates the effects of barley husk-derived water-soluble xylan (BH-WSX) on gut homeostasis and the microbiome. We enzymatically extracted BH-WSX and evaluated its prebiotic and antioxidant properties. A 40.0 % (w/v) xylan yield was achieved, with the extracted xylan having a molecular mass of 212.0885 and a xylose to glucuronic acid molar ratio of 6:1. Specialized optical rotation research indicated that the isolated xylan is composed of monomeric sugars such as D-xylose, glucose, and arabinose. Fourier Transform Infrared (FTIR) spectroscopy revealed that the xylan comprises β (1 → 4) linked xylose units, randomly substituted with glucose residues, α-arabinofuranose, and acetyl groups. Nuclear Magnetic Resonance (NMR) analysis showed that the barley husk extract's backbone is substituted with 4- O -methyl glucuronic acid at the O 2 position. Thermogravimetric analysis indicated that WSX exhibits a single sharp peak at 266 °C on the Differential Thermal Gravimetry (DTG) curve. Furthermore, a combination of in vitro, in vivo models, and molecular docking analysis elaborated on the anti-adhesion properties of BH-WSX. This study presents a novel approach to utilizing barley husk as an efficient source of functional polysaccharides for food-related industrial applications. • Enzyme-aided alkaline extraction enhanced polymeric xylan yield from barley husk effectively. • Extracted xylan demonstrated strong anti-biofilm activity. • Barley husk xylan showed high affinity for pathogen cell wall proteins in in silico analysis. • BH xylan's prebiotic effects and gut microbiota modulation were confirmed. [ABSTRACT FROM AUTHOR]

Hordeum vulgare husk, a cereal grain, is rich in dietary fiber and prebiotics beneficial for the gut microbiota and host organism. This study in v estigates the effects of barley husk-derived water-soluble xylan (BH-WSX) on gut homeostasis and the microbiome. We enzymatically extracted BH-WSX and evaluated its prebiotic and antioxidant properties. A 40.0 % (w/v) xylan yield was achieved, with the extracted xylan having a molecular mass of 212.0885 and a xylose to glucuronic acid molar ratio of 6:1. Specialized optical rotation research indicated that the isolated xylan is composed of monomeric sugars such as D-xylose, glucose, and arabinose. Fourier Transform Infrared (FTIR) spectroscopy revealed that the xylan comprises β (1 → 4) linked xylose units, randomly substituted with glucose residues, α-arabinofuranose, and acetyl groups. Nuclear Magnetic Resonance (NMR) analysis showed that the barley husk extract's backbone is substituted with 4- O -methyl glucuronic acid at the O 2 position. Thermogravimetric analysis indicated that WSX exhibits a single sharp peak at 266 °C on the Differential Thermal Gravimetry (DTG) curve. Furthermore, a combination of in vitro, in vivo models, and molecular docking analysis elaborated on the anti-adhesion properties of BH-WSX. This study presents a novel approach to utilizing barley husk as an efficient source of functional polysaccharides for food-related industrial applications. • Enzyme-aided alkaline extraction enhanced polymeric xylan yield from barley husk effectively. • Extracted xylan demonstrated strong anti-biofilm activity. • Barley husk xylan showed high affinity for pathogen cell wall proteins in in silico analysis. • BH xylan's prebiotic effects and gut microbiota modulation were confirmed. [ABSTRACT FROM AUTHOR]

[Display omitted] • We studied SOC fractions and microbial properties in three cover-cropped orchards in China. • Legume cover crops increased SOC more than non-legume covers (38% vs. 16%) • Legume cover crops enhanced enzyme activities, microbial necromass, and community diversity. • Non-legume cover crops negatively affected the ratio of BG to NAG. • Microbial properties dominated the changes in SOC physical fractions. Cover crops are one of the climate-smart agricultural practices used to increase soil organic carbon (SOC) sequestration. However, the SOC sequestration potential and underlying mechanisms under different cover crops, especially in orchard agroecosystems, have not been fully elucidated. Here, we investigated three orchards in China using SOC fractionation methods, high-throughput sequencing, and biomarker analysis. Our objectives were to determine the effect of cover crops on the physical fractions and chemical compositions of SOC, as well as on microbial properties, and to clarify why legume and non-legume cover crops sequester SOC differently. The results showed different increases in SOC between legume and non-legume cover crops (+38% vs. +16%) compared with those in the control plots without cover crops. Legume cover crops increased mineral-associated and particulate organic carbon, whereas non-legume cover crops increased mineral-associated organic carbon only. These differences were attributed to their distinct effects on microbial SOC transformation pathways. Legume cover crops positively impacted microbial pathways by increasing the availability of soil substrates and nitrogen, such as dissolved organic carbon (+84%), O-alkyl carbon (+18%), and ammonium nitrogen (+42%). These results were supported by the increases in carbon and nitrogen enzyme activities, microbial community diversity indices, the abundance of dominant fungal taxa (Sordariomycetes), microbial biomass carbon (+105%), and microbial necromass carbon (+47%). Non-legume cover crops might have induced microbial nitrogen starvation, decreasing the efficiency of microbial pathways, as evidenced by the low β-glucosidase to β-N-acetylglucosaminidase ratios (−7%) and the lack of significant changes in the bacterial Shannon index or microbial necromass carbon. In addition, redundancy analysis revealed that enzyme activity, the microbial community, and microbial necromass carbon collectively dominated the changes in the SOC physical fraction. Site-specific soil properties such as soil texture and nitrogen availability were important factors influencing SOC sequestration under cover crops. Our study provides essential insights for optimizing cover crop management to increase SOC sequestration in orchard agroecosystems. [ABSTRACT FROM AUTHOR]

• MOR outperforms MEA/MAE in CO 2 capture, excels in desorption. • At 7 M, MOR boosts desorption rate by 357.86 % over MEA. • MOR cuts energy use by 33.33% and lowers costs 7.89% vs. MEA. • Industrial potential for MOR due to high thermal stability, low corrosivity. The present study comprehensively evaluates the CO 2 capture performance of morpholine (MOR) at concentrations of 2 M, 5 M, and 7 M, comparing its effectiveness against conventional amines, monoethanolamine (MEA) and 2-(methylamino)ethanol (MAE). The assessment criteria include CO 2 absorption rate, desorption rate, cyclic capacity, regeneration energy consumption, and relative economic cost. Utilizing 13C Nuclear Magnetic Resonance (NMR) technology, we analyzed the variations in ion concentration of the amine solvents under different CO 2 loadings to reveal the reaction mechanisms of MOR with CO 2. Our results demonstrate that MOR outperforms MEA and MAE in CO 2 capture performance, particularly excelling in desorption efficiency. At a concentration of 7 M, MOR exhibited a 357.86% increase in average desorption rate and a 46% larger cyclic capacity compared to MEA. Additionally, MOR showed a 33.33% reduction in regeneration energy consumption and a 7.89% decrease in relative economic cost. The comprehensive evaluation method developed in this study indicates that MOR, with its high thermal stability and low corrosivity, maintains excellent CO 2 capture performance at high amine concentrations, suggesting it as a promising absorbent for industrial applications. The findings contribute to the optimization of amine-based CO 2 capture technologies and provide a robust framework for the selection and assessment of amine solvents, paving the way for more sustainable and cost-effective carbon capture solutions. [ABSTRACT FROM AUTHOR]

Soil organic carbon (SOC) originates from a complex mixture of organic materials, and to better understand its role in soil functions, one must characterise its chemical composition. However, current methods, such as solid‐state 13C nuclear magnetic resonance (NMR) spectroscopy, are time‐consuming and expensive. Diffuse reflectance spectroscopy in the visible, near infrared and mid‐infrared regions (vis–NIR: 350–2500 nm; mid‐IR: 4000–400 cm−1) can also be used to characterise SOC chemistry; however, it is difficult to know the frequencies where the information occurs. Thus, we correlated the C functional groups from the 13C NMR to the frequencies in the vis–NIR and mid‐IR spectra using two methods: (1) 2‐dimensional correlations of 13C NMR spectra and the diffuse reflectance spectra, and (2) modelling the NMR functional C groups with the reflectance spectra using support vector machines (SVM) (validated using 5 times repeated 10‐fold cross‐validation). For the study, we used 99 mineral soils from the agricultural regions of Sweden. The results show clear correlations between organic functional C groups measured with NMR and specific frequencies in the vis–NIR and mid‐IR spectra. While the 2D correlations showed general relationships (mainly related to the total SOC content), analysing the importance of the wavelengths in the SVM models revealed more detail. Generally, models using mid‐IR spectra produced slightly better estimates than the vis–NIR. The best estimates were for the alkyl C group (R2 = 0.83 and 0.85, vis–NIR and mid‐IR, respectively), and the O/N‐alkyl C group was the most difficult to estimate (R2 = 0.34 and 0.38, vis–NIR and mid‐IR, respectively). Combining 13C NMR with the cost‐effective diffuse reflectance methods could potentially increase the number of measured samples and improve the spatial and temporal characterisation of SOC. However, more studies with a wider range of soil types and land management systems are needed to further evaluate the conditions under which these methods could be used. Highlights: Diffuse reflectance spectroscopy was used to characterise and model SOC functional chemistry.NMR derived C functional groups could be modelled with vis‐NIR and mid‐IR diffuse reflectance spectra.The methods allow for characterisation of SOC chemical composition on whole mineral soil samples.The approach can improve the spatial and temporal characterisation of SOC composition. [ABSTRACT FROM AUTHOR]

Graphene nanoflakes have attracted a growing interest owing to their tunable and unique electronic, optical, and magnetic properties. In particular, recent breakthroughs in the on-surface synthesis and characterization of graphene nanoflakes exhibiting π -magnetism have shown their promising great potential for spintronic applications. In this context, a theoretical investigation on the relative energetic stability, 13C nuclear magnetic resonance (NMR) chemical shifts, magnetically induced currents, hyperfine shifts, and hyperfine coupling constants of graphene nanoflakes of hexagonal and triangular shape has been performed using the density functional theory (DFT). The role played by the size, shape, and atomic site position in the flake on the 13C isotropic chemical shift is thoroughly examined. As a general trend, considering only the orbital contribution, sites from the innermost region of the flake present lower chemical shifts than the ones close to the border and, for large enough systems, such values tend to converge to roughly the graphene one. For the open-shell flakes, the hyperfine shifts and coupling constants exhibit oscillatory behavior, with opposite signs for adjacent sites. The magnitude of these parameters is progressively reduced with the increase in the distance from the edge, where the largest values of excess spin density are concentrated. [Display omitted] ● NMR parameters of graphene nanoflakes are investigated through DFT based simulations. ● Flakes of different sizes and shapes (coronoids and triangulenes) are analyzed. ● Spin-state energy splittings and spin ground state are calculated for triangulenes. ● 13C NMR chemical shifts for coronoids show good correlation with the flake size and atomic site position. ● Spin density and hyperfine shifts show oscillatory behavior for adjacent sites in triangulenes. [ABSTRACT FROM AUTHOR]

Keteleeria evelyniana Mast. is a species of conifer native to southern China, Laos and Vietnam. The species has been listed as vulnerable in Vietnam. Oil samples have been isolated from leaves, twigs, roots and cones, and analyzed by combination of GC(FID), GC-MS and 13C NMR. The composition of leaf oil, dominated by α-pinene (37.8%) and β-pinene (17.9%), varied substantially from that previously reported. Twig, cone and root oil compositions are reported for the first time. Twig oil contained mainly (E)-β-caryophyllene (25.4%) accompanied by α-pinene (15.9%), limonene (15.4%). (E)-β-caryophyllene (40.8%) was predominant in root oil, followed by α-Pinene (27.9%) and α-humulene (8.1%). Lastly, the composition of cone oil was characterized by a high content of α-pinene (58.8%) followed by β-pinene (22.0%). The occurrence of the diterpene iso-abienol (1.3%) could be noted. It could also be highlighted that the conformers βα and ββ of (E)-β-caryophyllene have been evidenced by 13C NMR spectroscopy. [ABSTRACT FROM AUTHOR]

Deep Eutectic Solvent (DES) made with Glucose & Choline Chloride is an environmentally safe and sustainable technique for 2,6-diaryl piperidine-4-ones preparation. Starting with benzaldehyde, 2 or 4-hydroxybenzaldehyde, the preparation was carried out in ammonia using different ketones such as 2-pentanone, 3-pentanone, 2-propanone, 2-butanone. Under an atom-efficient method, all of the derivatives (a-f) were synthesized in good to outstanding yields. FT-IR, ¹HNMR, 13CNMR, and GC-MS spectral methods were used to characterize the synthesized compounds. Choline chloride-glucose DES as a solvent has benefits over volatile organic solvents commonly utilized in similar processes. [ABSTRACT FROM AUTHOR]

Illegal adulteration of melamine in animal feed and food has been widely studied. However, the risk of using substitute non-protein nitrogen substances still exists. In this study, we developed the 13C NMR method for the detection of non-protein nitrogen substance adulteration in animal feed. Three compounds, i.e., urea, melamine, and biuret, were used for method development. We found that the chemical shifts of the characteristic peaks in the carbon spectra of high-nitrogen adulterants were all between 150 and 170 ppm, whereas the chemical shifts of real protein peptide bonds (-CO–NH-) were between 170 and 180 ppm, demonstrating a good distinction between non-protein nitrogen and authentic protein. The method for analyzing melamine, urea, and biuret was validated. The R2 values were all above 0.99 within the calibration range of 0.05–2% (w/w). The limits of quantification of urea, melamine, and biuret were 0.0120%, 0.0660%, and 0.0806%, respectively. This method involves simple sample pretreatment and rapid detection while also providing high accuracy. All the sample information obtained by NMR detection does not require strict impurity removal. Compared with a previously reported 1H NMR method, the developed 13C NMR method does not require strict moisture removal to avoid active hydrogen exchange, and the interfering peak overlap is mitigated. [ABSTRACT FROM AUTHOR]

This paper constructed the molecular structures of four types of coal with different ranks and investigated the correlation between coal molecular structure and pyrolysis characteristics by using 13C NMR, XPS, TG-FTIR, and GC-MS. The results demonstrate that the structural model formulas of lignite (HM), weakly caking coal (RN), long-flame coal (CY), and gas coal (QM) are C104H111NO20S, C93H109NO13, C167H191NO15S, and C142H129N3O9S, respectively. The aromatic structural units of HM and RN consist of benzene and naphthalene, which are connected by ether bonds or aliphatic chains. The molecular structures of HM and RN contain a large amount -OH and -COOH, which are easily broken to generate gases, such as H2O, CO, and CO2 during pyrolysis. The gas yield of RN is 28.90%, which is higher than the others. The ether bonds in HM breakage to form groups are easily combined with each other to form tar, while the aliphatic chains in RN fracture to form fragments to generate gas. The light component (C≦10) is the dominant form of tar in HM and RN, with a content of 95.62% and 87.78%, respectively. Phenols are the dominant components in HM tar; alcohols are the primary components in RN tar. In CY, the aromatic structures consisted of benzene, naphthalene, anthracene, and phenanthrene; the aliphatic structures mainly included cycloalkanes and long-chain alkanes. The QM structural units are dominated by phenanthrene and naphthalene, with the highest aromaticity. The pyrolysis gas in CY and QM is composed of CH4; the tar component consists of alcohols, phenols, and alkanes. The coke yield in RN is the lowest at 52.84%, and QM is the highest at 80.20%. [ABSTRACT FROM AUTHOR]

Sesquiterpene lactones are found in plants of Asteraceae family, and endoperoxides are known for their antimalarial activity. Structural elucidation is a relevant aspect; however, it is not uncommon to find incorrect or incomplete structural assignments in the literature. Calculations based in quantum mechanics are frequently used to compute 1H and 13C NMR chemical shifts, and after comparing with the experimental data, the correct structure is established from diverse candidates. Targeting the synthesis of bioactive compounds, we envisaged the synthesis of a novel endoperoxide from the natural sesquiterpene lactone α‐santonin (2). Photochemical transformation of α‐santonin (2) to mazdasantonin (4) followed by photooxidation catalyzed by rose bengal afforded the novel endoperoxide 5. This new endoperoxide contains five stereogenic centers and is analogous to the antimalarial agent artemisinin (1). The relative configuration of the stereogenic centers of the endoperoxide were established by nuclear magnetic resonance (NMR) analyses and confirmed by theoretical calculations. All approaches were in complete agreement, and the structure of mazdasantonin endoperoxide was established as (3S,3aS,5aS,8R,9bS)‐3,6,6‐trimethyl‐3,3a,4,5,8,9b‐hexahydro‐2H‐5a,8‐epidioxynaphtho[1,2‐b]furan‐2,7(6H)‐dione. [ABSTRACT FROM AUTHOR]

The structure and complete nuclear magnetic resonance (NMR) assignments of orbifomitellic acid, a novel lanostane triterpene isolated from the fruiting bodies of a Gabonese Ganoderma orbiforme (Polyporaceae), are reported. Within the vast catalogue of lanostanes documented from Ganoderma spp., orbifomitellic acid is the first disclosing a –COOH group at C‐4. [ABSTRACT FROM AUTHOR]