磺化碱木质素和磺化碱木质素聚氧乙烯醚的溶液行为研究

分别制备了不同磺酸基含量的磺化碱木质素(SAL)、不同交联度和分子量的磺化碱木质素聚氧乙烯醚(SAL-PEG),采用动态光散射(DLS)法分别研究磺酸基含量和PEG非离子长链对SAL和SAL-PEG溶液行为的影响规律.结果表明,不同磺酸基含量(1.28~2.09 mmol/g)的SAL在1.0 g/L的水溶液中存在聚集行为,磺酸基含量的增加使SAL的分子舒展程度增加,聚集程度越弱;Na Cl的加入使SAL的分子舒展程度减小,聚集体发生解聚.不同PEG含量的SAL-PEG在1.0 g/L的水溶液中主要以单分子状态存在,聚集行为较弱,分子的流体动力学半径与其分子量和交联度成正比;Na Cl的加入使SAL-PEG的PEG非离子长链却被严重压缩,分子流体动力学半径显著减小,减小程度与其分子量和交联度成正比,但SAL-PEG的聚集程度仍然较弱.     

Mechanochemical Activation of Zinc and Application to Negishi Cross‐Coupling

A form independent activation of zinc, concomitant generation of organozinc species and engagement in a Negishi cross‐coupling reaction via mechanochemical methods is reported. The reported method exhibits a broad substrate scope for both C(sp³)–C(sp²) and C(sp²)–C(sp²) couplings and is tolerant to many important functional groups. The method may offer broad reaching opportunities for the in situ generation organometallic compounds from base metals and their concomitant engagement in synthetic reactions via mechanochemical methods.     

木质素活化及在木材胶粘剂中的应用进展

木质素是相对分子量较高的天然聚合物,由于具有苯酚结构利于制备木材胶粘剂,但是木质素本身反应活性低,一般都将其活化后再利用.而且,除了以往利用最多的造纸工业产生的木质素外,研究发现木材经过褐腐菌降解后残留主要成分是结构部分发生变化的木质素,这种可再生生物质资源以其自身的结构特点在合成胶粘剂上也有很大的优势,本文结合木质素胶粘剂应用中的问题,重点概述了活化木质素的各种方法及褐腐木质素在木材胶粘剂中的应用.     

Screening and Comparison of Lignin Degradation Microbial Consortia from Wooden Antiques

Lignin, which is a component of wood, is difficult to degrade in nature. However, serious decay caused by microbial consortia can happen to wooden antiques during the preservation process. This study successfully screened four microbial consortia with lignin degradation capabilities (J-1, J-6, J-8 and J-15) from decayed wooden antiques. Their compositions were identified by genomic sequencing, while the degradation products were analyzed by GC-MS. The lignin degradation efficiency of J-6 reached 54% after 48 h with an initial lignin concentration of 0.5 g/L at pH 4 and rotation speed of 200 rpm. The fungal consortium of J-6 contained Saccharomycetales (98.92%) and Ascomycota (0.56%), which accounted for 31% of the total biomass. The main bacteria in J-6 were Shinella sp. (47.38%), Cupriavidus sp. (29.84%), and Bosea sp. (7.96%). The strongest degradation performance of J-6 corresponded to its composition, where Saccharomycetales likely adapted to the system and improved lignin degradation enzymes activities, and the abundant bacterial consortium accelerated lignin decomposition. Our work demonstrated the potential utilization of microbial consortia via the synergy of microbial consortia, which may overcome the shortcomings of traditional lignin biodegradation when using a single strain, and the potential use of J-6 for lignin degradation/removal applications.     

Highly Porous Carbons Synthesized from Tannic Acid via a Combined Mechanochemical Salt-Templating and Mild Activation Strategy

Highly porous activated carbons were synthesized via the mechanochemical salt-templating method using both sustainable precursors and sustainable chemical activators. Tannic acid is a polyphenolic compound derived from biomass, which, together with urea, can serve as a low-cost, environmentally friendly precursor for the preparation of efficient N-doped carbons. The use of various organic and inorganic salts as activating agents afforded carbons with diverse structural and physicochemical characteristics, e.g., their specific surface areas ranged from 1190 m²·g⁻¹ to 3060 m²·g⁻¹. Coupling the salt-templating method and chemical activation with potassium oxalate appeared to be an efficient strategy for the synthesis of a highly porous carbon with a specific surface area of 3060 m²·g⁻¹, a large total pore volume of 3.07 cm³·g⁻¹ and high H₂ and CO₂ adsorption capacities of 13.2 mmol·g⁻¹ at −196 °C and 4.7 mmol·g⁻¹ at 0 °C, respectively. The most microporous carbon from the series exhibited a CO₂ uptake capacity as high as 6.4 mmol·g⁻¹ at 1 bar and 0 °C. Moreover, these samples showed exceptionally high thermal stability. Such activated carbons obtained from readily available sustainable precursors and activators are attractive for several applications in adsorption and catalysis.     

Effects of Alcell Lignin Methylolation and Lignin Adding Stage on Lignin-Based Phenolic Adhesives

To investigate the effects of lignin methylolation and lignin adding stage on the resulted lignin-based phenolic adhesives, Alcell lignin activated with NaOH (AL) or methylolation (ML) was integrated into the phenolic adhesives system by replacing phenol at various adhesive synthesis stages or directly co-polymerizing with phenolic adhesives. Lignin integration into phenolic adhesives greatly increased the viscosity of the resultant adhesives, regardless of lignin methylolation or adding stage. ML introduction at the second stage of adhesive synthesis led to much bigger viscosity than ML or AL introduction into phenolic adhesives at any other stages. Lignin methylolation and lignin adding stage did not affect the thermal stability of lignin based phenolic adhesives, even though lignin-based adhesives were less thermally stable than NPF. Typical three-stage degradation characteristics were also observed on all the lignin-based phenolic adhesives. Three-ply plywoods can be successfully laminated with lignin based adhesives, and it was interesting that after 3 h of cooking in boiling water, the plywoods specimens bonded with lignin-based phenolic adhesives displayed higher bonding strength than the corresponding dry strength obtained after direct conditioning at 20 °C and 65% RH. Compared with NPF, lignin introduction significantly reduced the bonding strength of lignin based phenolic adhesives when applied for plywood lamination. However, no significant variation of bonding strength was detected among the lignin based phenolic adhesives, regardless of lignin methylolation or adding stages.     

丹参木质素及其单体含量的测定

本文建立了一种准确、快速的检测丹参中木质素及其单体含量的方法.采用Klason法和紫外分光光度法分别对丹参根和茎中酸不溶性木质素(Klason木质素)和酸溶性木质素含量进行了测定;运用硫代酸解法并结合气相色谱-质谱法(GC-MS)分别对丹参根和茎中各木质素单体组成进行了分析.结果显示,总木质素在丹参根和茎中的含量分别为...     

Using Fractionation and Diffusion Ordered Spectroscopy to Study Lignin Molecular Weight.

Recent reports demonstrate that applications of the biopolymer lignin can be helped by the use of a fraction of the lignin which has an optimal molecular weight range. Unfortunately, the current methods used to determine lignin's molecular weight are inconsistent or not widely accessible. Here, an approach that relies on 2D DOSY NMR analysis is described that provides a measure of lignin's molecular weight. Consistent results were obtained using this well-established NMR technique across a range of lignins.     

Biotransformation of Aspen Lignin by the Fungus Trametes villosus

Quantitative ¹ H and ¹³ C NMR spectroscopies demonstrate that biotransformation of aspen wood by the fungusTrametes villosusresults in oxidation and destruction of lignin with cleavage of C-C alkyl-alkyl bonds in side chains and partial demethoxylation in addition to cleavage of lignocarbohydrate bonds. New C _ar -O-C bonds form while lignin is being destroyed at alkyl-alkyl bonds. Cleavage of rings and destruction of C _ar -C bonds was not observed.     

Mechanochemical Pd-Catalyzed Cross-Coupling of Arylhalides and Organozinc Pivalates

Cross-coupling reactions are essential tools in target molecule synthesis. However, the use of highly reactive organometallic reagents limits their applicability. Here, we present a mechanochemical Pd-catalyzed cross-coupling reaction between aryl halides and organozinc pivalates that can be carried out under ambient temperature and atmosphere. This operationally simple procedure affords a wide range of biaryl and aryl-heteroaryl derivatives in high yields and short times. The reaction tolerates various functional groups and can be realized on a synthetically useful scale. Its practical value was demonstrated in the short synthesis of the pharmaceutical diflunisal.     

木质素β-O-4单元的光化学和电化学降解:醚键断裂反应的一种应用*

醚键断裂反应既是有机化学的重要教学内容,又在现实世界中具有广泛应用。木质素是一类重要的生物质资源,其降解核心为碳-氧键断裂反应体系,具有重要的研究价值。对木质素β-O-4单元利用光化学和电化学降解的最新科研进展进行总结,可为醚键断裂反应的教学提供应用案例,拓展学生科学视野。     

Mechanochemical Radical Boronation of Aryl Diazonium Salts Promoted by Sodium Chloride

Arylboronates are helpful building blocks in organic synthesis. Here, we present an efficient mechanochemical synthesis of arylboronates from arene diazonium salts. Importantly, this transformation was significantly enhanced by sodium chloride, which probably promotes the decomposition of diazonium salts via anion exchange. Chloride anions also participate in the formation of strongly reducing Cl−B anion radical intermediate that promotes radical chain reaction. The reaction proceeds more efficiently with a small amount of polar solvent as a liquid-assisted grinding additive. Quantum chemical calculations support the mechanistic proposal.     

Anti‐Stokes Stress Sensing: Mechanochemical Activation of Triplet–Triplet Annihilation Photon Upconversion

The development of methods to detect damage in macromolecular materials is of paramount importance to understand their mechanical failure and the structure–property relationships of polymers. Mechanofluorophores are useful and sensitive molecular motifs for this purpose. However, to date, tailoring of their optical properties remains challenging and correlating emission intensity to force induced material damage and the respective events on the molecular level is complicated by intrinsic limitations of fluorescence and its detection techniques. Now, this is tackled by developing the first stress‐sensing motif that relies on photon upconversion. By combining the Diels–Alder adduct of a π‐extended anthracene with the porphyrin‐based triplet sensitizer PtOEP in polymers, triplet–triplet annihilation photon upconversion of green to blue light is mechanochemically activated in solution as well as in the solid state.     

Mechanochemical Activation of Iron Cyano Complexes: A Prebiotic Impact Scenario for the Synthesis of α‐Amino Acid Derivatives

Mechanochemical activation of iron cyano complexes by ball milling results in the formation of HCN, which can be trapped and incorporated into α‐aminonitriles. This prebiotic impact scenario can be extended by mechanochemically transforming the resulting α‐aminonitriles into α‐amino amides using a chemical route related to early Earth conditions.     

机械化学法制备金属-有机骨架及其复合物研究进展

金属-有机骨架(MOFs)是由金属离子/簇和多齿状有机配体通过配位键桥联而形成的多孔晶态材料。MOFs材料具有孔隙率高、比表面积大、尺寸可调、结构易修饰、功能多样化等特点,使其在气体吸附、分离和催化等方面都具有潜在应用价值。到目前为止,在MOFs合成的几种常见方法中,机械化学法(即在无溶剂或极少量溶剂的情况下研磨固体反应物进行的反应)作为一种清洁、绿色、高效的合成手段逐渐引起人们的关注。本综述总结了近年来机械化学合成MOFs及其复合物的典型进展,目的是为机械化学法合成MOFs及其复合材料提供一个通用而易于理解的概述。目前的研究进展表明,机械化学法是一种实用且环境友好的合成方法,为低成本、宏量生产MOFs及其复合物提供了可能。     

Peracetic Acid Depolymerization of Biorefinery Lignin for Production of Selective Monomeric Phenolic Compounds

Lignin is the largest source of renewable material with an aromatic skeleton. However, due to the recalcitrant and heterogeneous nature of the lignin polymer, it has been a challenge to effectively depolymerize lignin and produce high‐value chemicals with high selectivity. In this study, a highly efficient lignin‐to‐monomeric phenolic compounds (MPC) conversion method based on peracetic acid (PAA) treatment was reported. PAA treatment of two biorefinery lignin samples, diluted acid pretreated corn stover lignin (DACSL) and steam exploded spruce lignin (SESPL), led to complete solubilization and production of selective hydroxylated monomeric phenolic compounds (MPC‐H) and monomeric phenolic acid compounds (MPC‐A) including 4‐hydroxy‐2‐methoxyphenol, p‐hydroxybenzoic acid, vanillic acid, syringic acid, and 3,4‐dihydroxybenzoic acid. The maximized MPC yields obtained were 18 and 22 % based on the initial weight of the lignin in SESPL and DACSL, respectively. However, we found that the addition of niobium pentoxide catalyst to PAA treatment of lignin can significantly improve the MPC yields up to 47 %. The key reaction steps and main mechanisms involved in this new lignin‐to‐MPC valorization pathway were investigated and elucidated.     

Isolation of Functionalized Phenolic Monomers through Selective Oxidation and CO Bond Cleavage of the β‐O‐4 Linkages in Lignin

Functionalized phenolic monomers have been generated and isolated from an organosolv lignin through a two‐step depolymerization process. Chemoselective catalytic oxidation of β‐O‐4 linkages promoted by the DDQ/tBuONO/O₂ system was achieved in model compounds, including polymeric models and in real lignin. The oxidized β‐O‐4 linkages were then cleaved on reaction with zinc. Compared to many existing methods, this protocol, which can be achieved in one pot, is highly selective, giving rise to a simple mixture of products that can be readily purified to give pure compounds. The functionality present in these products makes them potentially valuable building blocks.     

Unclicking the Click: Metal-Assisted Mechanochemical Cycloreversion of Triazoles Is Possible

The mechanochemical cycloreversion of 1,2,3-triazole compounds, which serve as unusually stable building blocks in materials and biomolecular chemistry as a result of mild “click chemistry”, remains puzzling. We show that the hitherto discussed straight-forward retro-click mechanism of the 1,4-disubstituted isomer, even if Cu^I catalyzed, can be ruled out in view of more favorable activation free energies of destructive pathways. In stark contrast, the 1,5-regioiomer can undergo cycloreversion under rather mild mechanochemical conditions owing to its favorable response to the external force in conjunction with standard Ru^II catalysis.     

Selective cleavage of the linear ether bond in benzyl glycidyl ether and triphenylmethyl glycidyl ether by potassium alkalide as two-electron-transfer reagent

The linear ether bond was exclusively cleaved in benzyl glycidyl ether and triphenylmethyl glycidyl ether under the influence of K⁻, K⁺(15-crown-5)₂ (1), whereas the strongly strained three-membered oxacyclic ring remained undisturbed. Potassium glycidoxide and benzylpotassium were found as the primary reaction products of benzyl glycidyl ether with 1. Subsequently, benzylpotassium reacted with benzyl glycidyl ether giving the next potassium glycidoxide molecule and bibenzyl. Benzyl phenyl ether was used as a model compound to explain the mechanism of bibenzyl formation. The reaction of triphenylmethyl glycidyl ether with 1 resulted in potassium glycidoxide and stable triphenylmethylpotassium. After treating with a quenching agent a new glycidyl ether or glycidyl ester was obtained from potassium glycidoxide. These results were found when the reaction occurred at the excess of glycidyl ether. In another case, i.e. at the excess of 1 further reactions took place with the participation of potassium anions and various new compounds were observed in the reaction mixture after benzylation or methylation. Thus, the method of substrates delivery influences the course of studied processes in a decisive way.