Alcoholic Hydroxyl Research Articles

Reactive Oxygen Species-Mediated Photooxidation in a Full-Space Electric Field Catalyst: Selectivity and Activity Control of Intramolecular Alcohol Hydroxyl and Aldehyde Groups

Reactive Oxygen Species-Mediated Photooxidation in a Full-Space Electric Field Catalyst: Selectivity and Activity Control of Intramolecular Alcohol Hydroxyl and Aldehyde Groups

Influences of surface active-groups on the exothermic properties and oxidation of coal molecules

In this study, coal samples' reactive group contents were changed using extractants, and the effects of the reactive group contents spontaneous coal combustion were investigated using infrared spectroscopy, thermogravimetry/derivative thermogravimetry, and differential scanning calorimetry. The results showed that the coal samples' hydroxyl group contents decreased in the order ethylenediamine (3.832 %) > N-methyl-2-pyrollidone mixed solution (2.091 %) > petroleum ether (0.882 %) > toluene (0.495 %) and that the hydroxyl group content was inversely related to the characteristic temperature point. RDG analysis showed that ethylenediamine formed N–H–O hydrogen bonds with hydroxyl-group-bearing molecules, coal molecules formed C–H–O hydrogen bonds with NMP molecules, petroleum ether generated a cumulative dispersive force with aliphatic side chains, and toluene molecules' benzene rings formed a very stable spatial structure with coal molecules' benzene rings. The thermogravimetry/derivative thermogravimetry curves showed that because the characteristic temperature points of the extracted coal samples moved to the high-temperature region from T5 onward, the coal samples had to be heated to a higher temperature to reach the energy required for the reaction. From the DSC thermograms, the exergy decreased in the order toluene (110.68 J/g) > NMP (110.52 J/g) > ethylenediamine (78.29 J/g) > petroleum ether (65.45 J/g). With increasing temperature from T1 to T6, the Pearson correlation coefficients of the alcoholic and phenolic hydroxyl groups were calculated at −0.7, −0.72, −0.93, −0.84, −0.8, −0.8, and −0.93 and −0.72, −0.91, −0.83, −0.79, −0.815, and −0.91, respectively, indicating that the hydroxyl group content influenced the coal's spontaneous combustion more than the other groups' contents.

Exploring the relationship between lignin structure and antioxidant property using lignin model compounds

Lignin has a natural polyphenol structure that is expected to replace chemically synthesized antioxidants as a native antioxidant with biodegradable and convenient source characteristics. However, the improvement of the antioxidant property of lignin and its application as an antioxidant are still somewhat limited due to the lack of understanding of the relationship between specific lignin structures and antioxidant property. Therefore, the study of the relationship between lignin structure and antioxidant property is crucial to realize the high-quality application of lignin. In this experiment, the scavenging ability of free 1,1-diphenyl-2-picrylhydrazyl (DPPH·) radicals was determined for different grades of acetylated tannins, typical lignin model compounds and different structural units of milled wood lignin to investigate the relationship between lignin structure and antioxidant property. Based on the experimental results, some structure-activity relationships were proposed and the mechanism of the antioxidant property of lignin was discussed. The number of phenolic hydroxyl groups was linearly and positively correlated with antioxidant property, and the scavenging of DPPH radicals increased significantly with the increase in the number of methoxy groups in the model compounds. Moreover, aldehyde and carboxyl groups had a negative effect on the antioxidant property of lignin, while methoxy, alkyl and alcohol hydroxyl groups played a positive role. The guaiacyl (G) and syringyl (S) units favored the antioxidant property, so the difference in the content of structural units in lignin under certain conditions of phenolic hydroxyl content also affected the antioxidant property. Therefore, the antioxidant property of aspen milled lignin was higher than that of other milled lignin from different wood species. Finally, the mechanism of DPPH free radical scavenging by lignin was revealed to better understand the relationship between lignin structure and antioxidant property.

Crucial role of humic substance type in Cr(VI) reduction by humic substance-Fe(III) coprecipitates but not in adsorption

Wetlands exhibit a self-purification effect on Cr(VI) owing to the adsorption and reduction capabilities of their humic substance (HS)-Fe(III) coprecipitates. However, the similarities and differences in the adsorption and reduction of Cr(VI) by different types of HS-Fe(III) coprecipitates remains unknown. In this study, fulvic acid (FA)- and humic acid (HA)-Fe(III) coprecipitates were synthesized with initial C/Fe ratios ranging from 0.25 to 15, and a comparative analysis of their adsorption and reduction effects was conducted. The results showed that FA- and HA-Fe(III) coprecipitates exhibit similar abilities to adsorb Cr(VI) by forming inner-sphere complexes with ferrihydrite (Fh), as well as with FA/HA. The association between FA/HA and Fe(III) not only blocked certain FeOH adsorption sites, but also enhanced the electrostatic repulsion towards Cr(VI), resulting in a proportionate decrease in their adsorption ability. For reduction, inductive and intrinsic reduction were involved in both FA- and HA-Fe(III) coprecipitates. However, the synergism/antagonism differed with the inherent sites (e.g., phenolic hydroxyl, ArOH) and activated sites (e.g., alcoholic hydroxyl, AlOH). Based on the size differences between FA and HA, the AlOH contained in FA was more easily activated by Fe(III) than that in HA, owing to the shorter induction path required. Thus, consistent synergism was observed in FA-Fe(III) coprecipitates regardless of Fe(III) species. In contrast, synergism was only observed in HA-Fe(III) coprecipitates containing Fh, because the inductive ability of Fe(III) cations was too weak to activate AlOH through the longer path. Moreover, with irreversible consumption of AlOH, intrinsic reduction became the dominant pathway at concentrations >1 mM Cr(VI). The preferential elimination of ArOH subsequently led to a transition to antagonism. These outcomes deepen our scientifical understanding of the environmental effects of HS-Fe(III) coprecipitates and offer new perspectives for exploring their potential applications in the remediation of Cr-contaminated sites.

Enhancing temperature resistance of polymer gel fracturing fluids: The role of alcohol

The temperature resistance of polymer gel fracturing fluids is the key to ensure its application in deep oil and gas reservoirs. Currently, the methods to improve the temperature resistance of polymer gel fracturing fluids are mainly based on the additives commonly used in fracturing fluids, but rarely studied on improving the strength of crosslinked systems by strengthening its non-covalent interactions. Herein, we separately introduce ethanol and glycol into the partially hydrolyzed polyacrylamide (HPAM) crosslinked zirconium polymer gels to form the fracturing fluid system with higher temperature-resistant ability. The concentrations of the HPAM and crosslinking agent are all 0.6 wt%. After shearing at 120 °C and 170 s−1 for 1 h, the addition of ethanol and glycol can increase the retention viscosity of the polymer gels from 43 mPa s to 148 mPa s and 204 mPa s, respectively. Microscopic characterization demonstrates that the addition of ethanol and glycol makes the polymer gels more dense “honeycomb” and “dendritic” structures, which may be the main reasons for the temperature resistance enhancement of the system. Additionally, the molecular dynamics simulations show that the supramolecular interaction in the polymer gel system is greatly enhanced by the formation of hydrogen bonds when the alcohol is added at low concentrations. Meanwhile, the zirconium ions play a bridging role in connecting oxygen atoms in the carboxyl group in HPAM and oxygen in the alcohol hydroxyl group. The hydrogen bonds and O-Zr-O bridges can strengthen the non-covalent interactions of the system, inhibiting the destruction of polymer gel structure at high temperatures and enhancing its temperature resistance. However, when the alcohol concentration of the system is too high, the crosslinking strength of the polymer gels is weakened to different degrees due to the competitive effect of the alcohol on the crosslinking agent. Both experimental results and theoretical simulation further deepen the understanding of alcohol to improve the temperature resistance of polymer gels, and can promote the subsequent application of alcohol to polymer gel fracturing fluids for property enhancement.

Theoretical Insights into the Mechanism and Origin of Solvent-Dependent Selectivity in the Cyclization of Propargyl Alcohols for the Divergent Synthesis of N-Heterocycles.

This study elucidates the mechanisms and principles governing chemoselectivity in synthesizing two distinct N-heterocycles, benzimidazole thiazine and benzothiazole imidazole, through BF3•OEt2-catalyzed cyclization reactions of propargyl alcohols with benzimidazole thiols. Employing density functional theory calculations, we highlight the crucial role of fluorine source in influencing chemoselectivity. In DCM, BF3, as the catalytic center, coordinates with propargyl alcohol's hydroxyl group to form a precursor. Conversely, in DMF, [BF2•DMF]+, formed from DMF and BF3•OEt2, acts as the catalytic center, activating the propargyl alcohol's hydroxyl group. The mechanisms in both solvents involve sequential steps: B-O bond formation, C-O bond cleavage, S-C bond formation, hydrogen atom transfer (HAT), cyclization, and deprotonation. A notable difference is the HAT process: in DCM, it follows a 1,5-HAT process, while in DMF, BF4- formation from DMF and BF3•OEt2 provides a fluorine source and introduces steric hindrance, favoring a 1,6-HAT process and leading to unique chemoselectivity. This pioneering research showcases the impact of DMF on cyclization reactions, offering valuable insights for comprehending and designing reactions driven by fluorine sources. Crucially, our results propose an innovative reaction mechanism featuring lower potential energy surfaces, enhancing our understanding of the intricate interplay among reactants, catalysts, and solvents.

β-Enaminones and organic salts from 3-benzoyl-4‑hydroxy-6-phenyl-2H-pyran-2-one: Synthesis, X-ray crystal structural studies and antimicrobial activity

The reactivity of pyran-2,4‑dione 1 towards primary amines (propylamine and p-toluidine) and secodary amines (morpholine and piperidine) were investigated. The reactions were proceeded by replacement of the external alcoholic hydroxyl group with primary amine accompanied by loss of water molecule to give β-enamino-pyran-2,4-diones 2 and 3. In case of secondary amines, a transfer of the phenolic proton of pyrone ring to the secondary amine nitrogen leading to the formation of the corresponding quaternary ammonium salts of morpholine 4 and piperidine 5, respectively. The X-ray single crystal structures of 2 and 4 proved with no doubt the proposed structure based on the spectral characterization. The percentages of the H…H, O…H, and C…H interactions are in the range of 49.2–50.6 %, 19.6–19.8 and 27.6–28.6 %, respectively in case of 2 based on Hirshfeld topology analysis. For the two cationic units in 4, the C…H (15.9–18.5 %), H…H (42.9–43.1) and O…H (38.2–40.5 %) are the most important. The two anionic units showed different types of intermolecular interactions. In one unit, the O…H (23.4 %), C…H (28.4 %) and C…C (1.3 %) contacts are the most important while in the other anionic unit the O…H (23.3 %), C…H (26.7 %), C…O (5.7 %) and C…C (1.6 %) interactions are the most significant. The inhibition zones of 1 (18 mm), 4 (22 mm), and 5 (20 mm) indicated greater activity against S. aureus, compared to streptomycin (16 mm) and neomycin (13 mm). Compounds 1–5 showed nearly two-fold as much antifungicidal activity against C. albicans compared to some conventional medicines such as Neomycin and Streptomycin.

Characterization and properties of phenolic resin doped modified lignin

Phenolic resins occupy an important position in industrial applications, but phenol, one of the raw materials for synthesis, is a non-renewable resource. Lignin, as a natural polymer containing phenolic hydroxyl groups, alcohol hydroxyl groups and other reactive groups, can replace some of the phenol in the synthesis of phenolic resins, which can reduce the amount of phenol, thus reducing the cost of phenolic resins, while effectively promoting the high value-added use of renewable biomass resources. Due to its low reactivity, alkaline lignin is usually discharged as production waste, unaware that lignin macromolecules can be modified. In this paper, the phenolic monomers were obtained by acid-catalyzed depolymerization of DES (choline chloride/p-toluenesulfonic acid or choline chloride/lactic acid) from waste alkaline lignin, and the recovery rate of the DES solution during the catalytic treatment was more than 85 %, in which the main monomer was 2-methoxy-4-(1-propyl) phenol. The degradation of alkaline lignin is still favorable after five times of DES solvent recovery. The depolymerized lignin monomer replaced phenol by 50 wt% and then ternary co-polymerized with phenol and formaldehyde to form a biomass phenol-based phenolic resin, providing a green route for phenolic resin production. The cost of resin preparation was economically calculated, and it was found that the cost of resin after accumulating 4 cycles of DES treatment was only 51.1 % of that of pure phenolic resin. The density functional theory (DFT) was used to simulate the possible radical reactions in the intermediate process of phenolic resin reaction, to explore the microscopic mechanism and competition, to provide theoretical reference for further experimental realization of resin structure control and optimization, and to improve the theoretical system of resin synthesis.

Studies on the Biomimetic Synthesis of Marine Ladder Polyethers via Endo‐Selective Epoxide‐to‐Epoxonium Ring‐Opening Cascades

AbstractMarine ladder polyethers have attracted the attention of chemists and biologists because of their potent biological activities. Synthetic chemists have attempted to construct their polyether frameworks by epoxide ring‐opening cascades, as Nakanishi hypothesis describes. However, Baldwin's rules of ring closure state that exo‐selective intramolecular cyclization of epoxy alcohols is preferred over endo‐selective cyclization. Herein, we investigated epoxide ring‐opening cascades of polyepoxy alcohols in [EMIM]BF4/PFTB (1‐ethyl‐3‐methylimidazolium tetrafluoroborate /perfluoro‐tert‐butyl alcohol) and found that all‐endo products were formed via epoxide‐to‐epoxonium ring‐opening cyclizations (not restricted by Baldwin's rules, which only apply to intramolecular hydroxyl‐to‐epoxide cyclizations). We determined that the key factor enabling polyepoxy alcohols to undergo a high proportion of all‐endo‐selective cyclization was inhibition of exo‐selective hydroxyl‐to‐epoxide cyclization starting from the terminal hydroxyl group of a polyepoxy alcohol. By introducing a slow‐release protecting group to the terminal hydroxyl group, we could markedly increase the cyclization yields of polyether fragments with hydrogen atoms at the ring junctions. For the first time, we constructed consecutively fused six‐membered‐ring and fused seven‐, eight‐, and nine‐membered‐ring polyether fragments by epoxide‐to‐epoxonium ring‐opening cyclizations through the addition of a suitable Lewis acid. We also suggest that the biosynthesis of marine ladder polyethers may proceed via epoxide‐to‐epoxonium ring‐opening cyclization of polyepoxide.

Studies on the Biomimetic Synthesis of Marine Ladder Polyethers via Endo-Selective Epoxide-to-Epoxonium Ring-Opening Cascades.

Marine ladder polyethers have attracted the attention of chemists and biologists because of their potent biological activities. Synthetic chemists have attempted to construct their polyether frameworks by epoxide ring-opening cascades, as Nakanishi hypothesis describes. However, Baldwin's rules of ring closure state that exo-selective intramolecular cyclization of epoxy alcohols is preferred over endo-selective cyclization. Herein, we investigated epoxide ring-opening cascades of polyepoxy alcohols in [EMIM]BF4/PFTB (1-ethyl-3-methylimidazolium tetrafluoroborate /perfluoro-tert-butyl alcohol) and found that all-endo products were formed via epoxide-to-epoxonium ring-opening cyclizations (not restricted by Baldwin's rules, which only apply to intramolecular hydroxyl-to-epoxide cyclizations). We determined that the key factor enabling polyepoxy alcohols to undergo a high proportion of all-endo-selective cyclization was inhibition of exo-selective hydroxyl-to-epoxide cyclization starting from the terminal hydroxyl group of a polyepoxy alcohol. By introducing a slow-release protecting group to the terminal hydroxyl group, we could markedly increase the cyclization yields of polyether fragments with hydrogen atoms at the ring junctions. For the first time, we constructed consecutively fused six-membered-ring and fused seven-, eight-, and nine-membered-ring polyether fragments by epoxide-to-epoxonium ring-opening cyclizations through the addition of a suitable Lewis acid. We also suggest that the biosynthesis of marine ladder polyethers may proceed via epoxide-to-epoxonium ring-opening cyclization of polyepoxide.

Preparation of Cross-Linked Sodium Alginate Microspheres with Different Metal Ions Using the Microfluidic Electrospray Technology.

Microspheres are micrometer-sized particles that can load and gradually release drugs via physical encapsulation or adsorption onto the surface and within polymers. In the field of biomedicine, hydrogel microspheres have been extensively studied for their application as drug carriers owing to their ability to reduce the frequency of drug administration, minimize side effects, and improve patient compliance. Sodium alginate (ALG) is a naturally occurring linear polysaccharide with three backbone glycosidic linkages. There are two auxiliary hydroxyl groups present in each of the moieties of the polymer, which have the characteristics of an alcohol hydroxyl moiety. The synthetic ALG units can undergo chemical cross-linking reactions with metal ions, forming a cross-linked network structure of polymer stacks, ultimately forming a hydrogel. Hydrogel microspheres can be prepared using a simple process involving the ionic cross-linking properties of ALG. In this study, we prepared ALG-based hydrogel microspheres (ALGMS) using a microfluidic electrodeposition strategy. The prepared hydrogel microspheres were uniformly sized and well-dispersed, owing to accurate control of the microfluidic electrospray flow. ALGMS cross-linked with different metal ions were prepared using a microfluidic electrospray technique combining microfluidic and high electric field, and its antimicrobial properties, slow drug release ability, and biocompatibility were investigated. This technology holds promise for application in advanced drug development and production.

Ga(OTf)3 catalysed rapid nucleophilic substitution of propargyl alcohols with enoxysilanes

Ga(OTf)3 efficiently catalyses the nucleophilic substitution of the hydroxyl group of propargyl alcohols with enoxysilanes to aid in CC bond formation. The reactions can be performed in an undried solvent under air to obtain the desired products quickly in good yields. Other nucleophiles, such as indole, phenol, and furan are also suitable for this transformation. The use of inexpensive and readily available catalysts makes this method simple, convenient, and practical.

Construction of a food waste biochar model and determination of contaminant adsorption sites: Combining experimental characterisation with quantum chemical calculations

Increasing urbanization has made it a serious challenge to deal with food waste (FW) from people and wastewater with pollutants from industry. Biochar from FW pyrolysis(FWB) can be used as an adsorbent to adsorb pollutants from wastewater, but its molecular structure is still unknown, limiting the understanding of its adsorption mechanism and its application in industry. In this paper, a series of combined methods of experimental characterization and quantum chemical calculations, such as solid-state 13C nuclear magnetic resonance spectroscopy (13C NMR), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) were used to investigate and successfully construct a model of the molecular structural features of FWB under the optimal contaminant adsorption preparation conditions. Based on the electrostatic potential distribution and adsorption experiments, the adsorption sites of the pollutants were elucidated. The results showed that the FWB prepared at different temperatures, 450 °C had a variety of oxygen-containing functional groups and polarity favorable for adsorption. In the molecular structure of FWB with the molecular formula C60H49N7O8, oxygen is present in the form of carboxyl, carbonyl, ether, alcohol hydroxyl, and phenol hydroxyl groups with numbers 1, 1, 1, 1, 2, 1, 2. Nitrogen is present in the form of pyridinyl nitrogen, pyrrolidinyl nitrogen, and primary amines with numbers 1, 1, and 5, respectively. In addition, nitrogen-containing and oxygen-containing functional groups are possible adsorption sites for pollutants on FWB, and alcohol hydroxyl and amino groups can bind better to Cu2+, which provides scientific guidance for improving the adsorption performance of biochar. This provides a solid foundation for the study of the microscopic adsorption mechanism of FWB and a method for the modeling of biochar from other biomasses.

Excellent interfacial compatibility of phase change capsules/polyurethane foam with enhanced mechanical and thermal insulation properties for thermal energy storage

The incorporation of phase change microcapsule (microPCMs) substantially augmented the temperature regulation capacity of foams, endowing it with outstanding application potential in numerous industrial domains. However, interfacial compatibility issues between the capsule and the substrate always exist and affect foam performance. In this study, a milli-meter macrocapsule (macroPCMs) containing microPCMs was prepared using calcium alginate gel as the second layer wall to physically improve the interfacial compatibility. And poly (N-hydroxymethyl acrylamide) was in situ polymerized in the gel layer and provided active alcohol hydroxyl groups to form chemical grafting with the polyurethane raw materials, which further chemically improved the interfacial compatibility. These measures created a significantly improved foam microstructure and a greatly increased foaming capacity, which thus endow the composite foam with excellent thermal insulation performance and mechanical strength. Compared with conventional microPCMs-based foam, the foaming capacity of the macroPCMs-based foam increased by 40 folds, the temperature regulation duration increased by 7 folds, and the mechanical performance increased by 3 folds. Moreover, the insulated incubator fabricated with the macroPCMs-based foam exhibited two-fold greater thermal insulation efficiency than conventional models containing internal ice incubator, which validated the potential of employing macroPCMs-based polyurethane foam in cold chain logistics applications.

Nitrogen-doped ordered mesoporous carbon supported ruthenium metallic nanoparticles: Opportunity for efficient hydrogenolysis of biomass-derived 5-hydroxymethylfurfural to 2,5-dimethylfuran by catalytic transfer hydrogenation

One of the most promising solutions to the current energy crisis is an efficient catalytic transformation of abundant low-cost renewable raw biomass into high-quality biofuel. Herein, a highly effective catalyst was constructed systematically for the selective synthesis of 2,5-dimethylfuran (DMF) biofuel from biomass-derived 5-hydroxymethylfurfural (HMF) via green catalytic transfer hydrogenolysis (CTH) using a nitrogen-doped ordered mesoporous carbon (N-CMK-1) decorated ruthenium (Ru)-based catalyst in i-propanol as hydrogen source. The structures and properties of different catalysts were characterized by different characterization techniques such as FTIR, XRD, N2-sorption, CO2-sorption, TGA, TEM, ICP-AES, CHNO analysis, and acid-base back titration. A complete HMF conversion with a high DMF yield of 88% was achieved under optimized reaction conditions. Regarding substrate conversion and product yield, the influence of reaction temperature, time, and hydrogen donors was thoroughly investigated. The nitrogen-promoted carbon support enhanced the dispersion of Ru due to the formation of appropriate basic site density which could efficiently promote the activation of alcohol hydroxyl in i-propanol and subsequent release of active hydrogen species. In the meantime, highly dispersed surface Ru nanoparticles (NPs) were beneficial for hydrogen transfer and activation of both carbonyl and hydroxyl groups in HMF. Moreover, Arrhenius kinetic analysis was studied by identifying 5-methyl furfural (5-MF) and 2,5-bishydroxymethylfuran (BHMF) as two key intermediates that dominate a distinct reaction pathway during hydrogenolysis of HMF to DMF via CTH. Furthermore, high stability without obvious loss of activity after three consecutive cycles was observed in a fabricated N-CMK-1 decorated Ru-based catalyst as a result of superior metal-support interaction and the mesoporous framework nature of the catalyst. These findings would not only offer a robust catalyst synthetic approach but also open a new avenue for the exploitation of biomass to specialty chemicals and advanced biofuels.

Mutability landscape guided engineering of a promiscuous microbial glycosyltransferase for regioselective synthesis of salidroside and icariside D2

Microbial glycosyltransferases efficiently synthesize glucosides and have garnered increasing interest. However, limited regioselectivity has impeded their broad application, particularly in the pharmaceutical industry. In this study, the UDP-glycosyltransferase YjiC from Bacillus licheniformis (BlYjiC) was engineered to achieve the bidirectional regioselective glycosylation of tyrosol and its derivatives. Initially, site-directed saturation mutagenesis was performed on two newly identified substrate-binding cavities in the acceptor pocket of BlYjiC to provide a comprehensive blueprint of the interplay between mutations and function (mutability landscape). Iterative saturation mutagenesis was performed, guided by the mutability landscape. Two highly regioselective mutants M6 (M112L/I325Y/L70R/Q136E/I67E/M77R) and M2’ (M112D/I62L) were generated, exhibiting >99 % regioselectivity toward the alcoholic and phenolic hydroxyl of tyrosol, respectively, compared with the wild-type (product mixture: 51:49 %). Both mutants exhibited excellent regioselectivity toward several dihydroxy phenolic substrates, offering valuable biocatalysts for the regioselective synthesis of glucosides. Their application was confirmed in a short synthesis of salidroside (3.6 g/L) and icariside D2 (2.4 g/L), which exhibited near-perfect regioselectivity. This study provides valuable insights into future protein engineering of similar enzymes and opens new avenues for their practical applications.

Revealing the roles of the dual active-sites on a polyoxometalate-based metal–organic framework in catalyzing Knoevenagel condensations

The efficient catalysis of Knoevenagel condensations under mild conditions is a significant way for obtaining olefin compounds, which can be used to produce a wide range of biologically active heterocyclic chemicals and fine chemical raw materials. Herein, a novel polyoxometalate-based metal–organic framework (POMOF), [Co(bix)(H2O)]{V2O6} (VMOF-1, bix = 1,4-bis(imidazol-1-ylmethyl)benzene), is synthesized and structurally characterized. After removal of the coordinated water molecules of CoII ions by vacuum drying, VMOF-1a with both Lewis acid and Lewis base catalytic active-centers is achieved. VMOF-1a as the heterogeneous catalyst for the conversion of benzaldehyde and malononitrile to high value-added olefinic compounds under mild conditions, exhibits excellent conversion and selectivity, good recyclability and broad substrate applicability. Experimental and theoretical studies have revealed that CoII ion and {V2O6}2− unit in VMOF-1a synergistically catalyze the Knoevenagel condensation reaction: (1) {V2O6}2− is used as a Lewis base to pull out the proton of the active methylene group on malononitrile; (2) CoII ion acts as a Lewis acid to activate the carbonyl oxygen on benzaldehyde. Furthermore, it is demonstrated for the first time that the Lewis acid sites in POMOF can play the role of stabilize the alcohol hydroxyl anion intermediates generated during the reaction process, which further elucidates the reason for the high catalytic activity of VMOF-1a in the Knoevenagel condensation. This study provides theoretical guidance for the design of efficient and sustainable catalysts for Knoevenagel condensation.

Rac-Hy-droxy-isovaleric acid.

The title compound (systematic name: rac-2-hydroxy-3-methylbutanoic acid), C5H10O3, is the constitutional isomer of α-hy-droxy-butanoic acid. In the crystal, hydrogen bonds involving the alcoholic hydroxyl group give rise to centrosymmetric dimers that are extended to sheets perpendicular to the crystallographic c axis.

The effect of composite curing agent ratio on the photooxidative aging behavior of epoxy asphalt based on molecular dynamics simulation

In order to explore the effect of composite curing agent ratio on the photooxidative aging behavior of epoxy asphalt with an acidic composite curing system, three curing agent ratios of epoxy asphalt were prepared to obtain different cross-linking network densities. The prepared epoxy asphalt was subjected to photooxidation aging for 240 h at 60 ℃. Fourier transform infrared (FTIR) and elemental analysis tests were conducted to determine the evolution of chemical components during photooxidative aging. Based on the chemical components before and after aging, molecular models of photooxidation aged epoxy asphalt with different curing agent ratios were constructed. The mean square displacement (MSD) of oxygen atoms and the oxygen uptake of each component were calculated to study the diffusion behavior of oxygen atoms and the oxidation degree of each component under various cross-linking networks. Glass transition temperature (Tg) and interaction energy were determined to characterize the thermodynamic properties and interaction between asphalt phase and epoxy resin phase of epoxy asphalt before and after aging. The radial distribution function (RDF) was determined to simulate the distribution of asphaltene and epoxy resin crosslinked networks in different cross-linking networks. The results show that the formation of carbonyl groups, alcohol hydroxyl groups, and the fracture of methylene groups was observed during the photooxidative aging process of epoxy asphalt. The rise in the proportion of anhydride curing agents improved the stability of the chemical components in epoxy asphalt under photooxidation aging. High cross-linking density and methylene fracture weakened the diffusion ability of oxygen atoms in epoxy asphalt due to a reduction in free volume. In addition, photooxidation aging had a negative impact on the low-temperature performance and interaction between asphalt phase and epoxy resin phase of epoxy asphalt. However, a high content of acid anhydride alleviated the damage of photooxidation aging to low-temperature performance. Photooxidation aging developed the polar functional groups of epoxy asphalt, promoting the stacking of asphaltene under a high content of dicarboxylic acid curing agent, while breaking the stacking of asphaltene under a high content of acid anhydride curing agent.

Renewable thermoplastic starch/sugar alcohol blends and their oxygen barrier application

AbstractFully renewable oxygen barrier thermoplastic starch (TPS)/sugar alcohol blown films were innovatively prepared by blending proper loadings of Erythritol (ET), Sorbitol (ST), and Lactitol (LT) and supercritical carbon dioxide (scCO2) assistance. The oxygen transmission rate (OTR) values of the properly prepared scCO2TPSxETy, scCO2TPSxSTy, and scCO2TPSxLTy films reduced to 4.3, 6.6, and 12.5 cm3/m2∙day∙atm, which are about 5–28 times smaller than those of the conventional TPS films reported in the literature. The free‐volume‐cavity characteristics (FVCC) and OTR detected for TPSxETy (or scCO2TPSxETy), TPSxSTy (or scCO2TPSxSTy), and TPSxLTy (or scCO2TPSxLTy) films diminished to a minimum, as their ET, ST and LT loadings came near an optimal value. Slightly smaller OTR and FVCC values were detected for scCO2TPSxETy, scCO2TPSxSTy, and scCO2TPSxLTy films than those of corresponding TPSxETy, TPSxSTy, and TPSxLTy films prepared without scCO2‐assistance. The smallest OTR and FVCC detected for the properly prepared TPSxETy (or scCO2TPSxETy), TPSxSTy (or scCO2TPSxSTy), and TPSxLTy (or scCO2TPSxLTy) films diminished with decreasing sugar alcohol's molecular weight. An essential result is that the OTR of the properly prepared scCO2TPSxETy film was merely 4.3 cm3/m2∙day∙atm, which is small enough to meet the demand of high oxygen barrier packaging application. Dynamic molecular relaxations detected for these films disclosed that ET, ST, and LT were compatible with TPS, as their loads were ≤ the optimum value. The distinctly reduced OTR and FVCC for these properly prepared films are partially attributed to the reinforced molecular interactions between sugar alcohol and TPS's hydroxyl groups when they were prepared with scCO2‐assistance, optimal sugar alcohol loading, and/or smaller sugar alcohol's molecular weight.Highlights High oxygen barrier thermoplastic starch/sugar alcohol blown films were prepared. The lowest oxygen transmission rate of the renewable film was 4.3 cm3/m2∙day∙atm. This oxygen transmission rate is qualified for high oxygen barrier application. Boosted oxygen barrier property was ascribed to the reduced free volume values.