ChemRxiv最新文献_第2页

Confined hot-pressurized water in Brønsted-acidic Beta zeolite speeds up the O-demethylation of guaiacol 布氏酸性 Beta 沸石中的封闭热压水加速了愈创木酚的 O-脱甲基反应

ChemRxiv Pub Date : 2024-09-19 DOI: 10.26434/chemrxiv-2024-ll505

Massimo, Bocus, Elias, Van Den Broeck, Xian, Wu, Mathias, Bal, Jeroen, Bomon, Louis, Vanduyfhuys, Bert F., Sels, Bert U. W., Maes, Veronique, Van Speybroeck

{"title":"Confined hot-pressurized water in Brønsted-acidic Beta zeolite speeds up the O-demethylation of guaiacol","authors":"Massimo, Bocus, Elias, Van Den Broeck, Xian, Wu, Mathias, Bal, Jeroen, Bomon, Louis, Vanduyfhuys, Bert F., Sels, Bert U. W., Maes, Veronique, Van Speybroeck","doi":"10.26434/chemrxiv-2024-ll505","DOIUrl":"https://doi.org/10.26434/chemrxiv-2024-ll505","url":null,"abstract":"New lignocellulose biorefinery technologies that enable the conversion of lignin into platform chemicals are essential to reduce our future dependence on fossil resources. In this study, we investigate the Brønsted acid-catalyzed O-demethylation of guaiacol in hot-pressurized water (HPW) as a model reaction for transforming lignin-derived phenolic substrates featuring ortho methoxy groups. We compare the effects of Brønsted mineral acid (HCl) and microporous solid acid (H-BEA zeolite) in water to elucidate the hydrolysis mechanism and the impact of zeolite microporosity on reaction rates. Operando molecular modeling combined with experimental kinetic studies reveals that, regardless of the catalyst type, O-demethylation follows a concerted, one-step O-activated SN2 mechanism. This mechanism involves a strong hydrogen bond between guaiacol and a hydronium ion as an ionic contact pair. Protons confined within the zeolite form more active undercoordinated hydronium ions, which are associated with lower enthalpic requirements and thus accelerate the hydrolysis. The molecular organization of solvent and reactants around the confined catalytic active site plays a crucial role in modulating the association of the reacting species. These proof-of-concept results demonstrate the significant influence of solvent (water) coordination on acid-catalyzed bimolecular reactions, such as hydrolysis, within confined spaces.","PeriodicalId":9813,"journal":{"name":"ChemRxiv","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142267244","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Bifunctional photocatalysts display proximity-enhanced catalytic activity in metallaphotoredox C–O coupling 双功能光催化剂在金属光氧 C-O 偶联中显示出近似增强的催化活性

ChemRxiv Pub Date : 2024-09-19 DOI: 10.26434/chemrxiv-2024-qgsl2

Luca, Pignataro, Luigi, Dolcini, Andrea, Solida, Daniele, Lavelli, Andrés Mauricio, Hidalgo-Núñez, Tommaso, Gandini, Matthieu, Fornara, Alessandro, Colella, Alberto, Bossi, Marta, Penconi, Daniele, Fiorito, Cesare, Gennari, Alberto, Dal Corso

{"title":"Bifunctional photocatalysts display proximity-enhanced catalytic activity in metallaphotoredox C–O coupling","authors":"Luca, Pignataro, Luigi, Dolcini, Andrea, Solida, Daniele, Lavelli, Andrés Mauricio, Hidalgo-Núñez, Tommaso, Gandini, Matthieu, Fornara, Alessandro, Colella, Alberto, Bossi, Marta, Penconi, Daniele, Fiorito, Cesare, Gennari, Alberto, Dal Corso","doi":"10.26434/chemrxiv-2024-qgsl2","DOIUrl":"https://doi.org/10.26434/chemrxiv-2024-qgsl2","url":null,"abstract":"Dual catalytic reactions may be made more effective through an improved integration of the catalytic cycles achieved using bifunctional catalysts. Herein we describe new bifunctional photocatalysts consisting of a photoactive donor-acceptor cyanoarene unit linked to a bipyridine ligand moiety that can bind transition metals. The bifunctional photocatalysts were synthesized in 3-5 steps form commercially available compounds and fully characterized in terms of photophysical properties, which are strongly affected by the type of linkage used (C vs. O) to connect the cyanoarene core to the ligand. Catalytic tests carried out in the Nicatalyzed C-O cross-coupling of alcohols to aryl bromides promoted by visible light have shown that the bifunctional systems are more active than the corresponding ‘dual catalytic systems’ (i.e., not covalently bound), taking advantage of the proximity between the two catalytic moieties (Ni-complex and photocatalyst). The best bifunctional dyes were tested with several alcohols and aryl halides, giving good yields at low catalytic loading (0.5-2 mol%).","PeriodicalId":9813,"journal":{"name":"ChemRxiv","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142267247","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Oxygen Adsorption at the Electrochemical Metal/Water Interface: Au(111) vs Pt(111) 电化学金属/水界面的氧气吸附：金（111）与铂（111）

ChemRxiv Pub Date : 2024-09-19 DOI: 10.26434/chemrxiv-2024-xdl01

Vanessa J., Bukas, Alexandra M., Dudzinski, Elias, Diesen, Karsten, Reuter

{"title":"Oxygen Adsorption at the Electrochemical Metal/Water Interface: Au(111) vs Pt(111)","authors":"Vanessa J., Bukas, Alexandra M., Dudzinski, Elias, Diesen, Karsten, Reuter","doi":"10.26434/chemrxiv-2024-xdl01","DOIUrl":"https://doi.org/10.26434/chemrxiv-2024-xdl01","url":null,"abstract":"Reaction mechanisms in heterogeneous electrocatalysis have been known to change through the local field that arises at the electrified metal/liquid interface. First-principles simulations specifically predict that such a field can significantly modify the surface binding of dipolar or polarizable intermediates along a catalytic reaction path. This dependence can then lead to a corresponding dependence upon applied potential even for so-called ‘chemical’ reaction steps that do not involve an explicit proton-coupled-electron-transfer such as, e.g., O2 adsorption during the oxygen reduction reaction (ORR). And yet, such effects are only now starting to be systematically explored at the atomic level. In this study, we directly compare the potential dependence of O2 adsorption as the first ORR step on Au(111) vs Pt(111). Using ab initio molecular dynamics and free energy sampling, we find that the strong dependence previously predicted at Au(111) is specifically lost at Pt(111). By decoupling the O2 potential response into contributions of different physical origin, we explain this contrast through the inherently different reactivity of the two metals. We finally discuss an indirect effect of potential through the surface coverage that can promote a dissociative-type mechanism at Pt(111) by breaking the O-O bond already during the first step of the ORR mechanism. Our results thus overall suggest a more complex mechanistic picture than hitherto anticipated; one where the local field may manifest in different, yet potentially equally important, ways over different systems.","PeriodicalId":9813,"journal":{"name":"ChemRxiv","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142267248","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Metal-Organic Frameworks for the Trace Multiplexed Quantitation of 50 PFAS by Liquid Chromatography Mass Spectrometry 通过液相色谱质谱法对 50 种全氟辛烷磺酸进行痕量多重定量的金属有机框架

ChemRxiv Pub Date : 2024-09-19 DOI: 10.26434/chemrxiv-2024-qkvkd

William, Donald, Lisa, Hua, Marcello, Solomon, Deanna, D'Alessandro

{"title":"Metal-Organic Frameworks for the Trace Multiplexed Quantitation of 50 PFAS by Liquid Chromatography Mass Spectrometry","authors":"William, Donald, Lisa, Hua, Marcello, Solomon, Deanna, D'Alessandro","doi":"10.26434/chemrxiv-2024-qkvkd","DOIUrl":"https://doi.org/10.26434/chemrxiv-2024-qkvkd","url":null,"abstract":"Per- and polyfluoroalkyl substances (PFAS) are environmental contaminants of increasing concern due to their persistence and potential health impacts. New guidelines with exceedingly low detection limits necessitate the development of promising materials for preconcentration. Six different metal-organic frameworks were evaluated for their potential as dispersive solid-phase extraction (dSPE) sorbents for PFAS quantitation by quantitative liquid chromatography tandem mass spectrometry (LC-MS/MS). UiO-66 demonstrated the highest combined average adsorption (87%) and recovery (85%) across 33 PFAS spiked in water at 2 ppb, and 75% recovery for 50 PFAS at 200 ppq. The developed dSPE workflow using UiO-66 resulted in limit of detections (LODs) as low as 4 ppq with average LODs of 108 ppq across 50 PFAS by testing at concentrations of 200 to 800 ppq. UiO-66 retained its crystalline structure post-PFAS adsorption, indicating stability for dSPE. Nearly 100% average recovery across all 50 PFAS was observed for UiO-66 using a 20 ppt spike, whereas ZIF-8 resulted in lower recovery. The efficacy of using UiO-66 as a dSPE material was assessed using six environmental water samples from different locations in Sydney, Australia, with all samples having quantifiable levels of PFAS. In water collected from Sydney Airport, 22 PFAS were detected above the limit of quantification (LOQ). Across all environmental water samples, a total of 25 PFAS were quantified above LOQs, with internal standard recoveries between 70-120%. In addition, the presence of multiply charged counterions decreased short-chained PFAS adsorption, while chloride had no impact. While polymeric resins have been used for screening ~50 PFAS with limits of detection ranging from 1 to 80 ppt, UiO-66 can be used to detect 50 PFAS at concentrations as low as 200 ppq. The high performance of UiO-66 in terms of recovery and detection limits underscores its potential for practical analytical applications in PFAS detection.","PeriodicalId":9813,"journal":{"name":"ChemRxiv","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142267374","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Base-free palladium-catalyzed borylation of enol carboxylates and further reactivity toward deboronation and cross-coupling 烯醇羧酸酯的无碱钯催化硼酸化反应以及去硼酸化和交叉偶联的进一步反应性

ChemRxiv Pub Date : 2024-09-19 DOI: 10.26434/chemrxiv-2024-5mlml

David, Leitch, Gregory, Gaube, Douglas, Miller, Rowan, McCallum, Nahiane, Pipaon Fernandez

引用次数: 0

Unveiling the mysterious hydrocarbon – Clar’s goblet 揭开神秘碳氢化合物--克拉尔高脚杯的面纱

ChemRxiv Pub Date : 2024-09-19 DOI: 10.26434/chemrxiv-2024-ks6xm

Jishan, Wu, Tianyu, Jiao, Cong-Hui, Wu, Yu-Shuang, Zhang, Xiaohe, Miao, Shaofei, Wu, Shang-Da, Jiang

引用次数: 0

From new thermodynamics to classical mechanics 从新热力学到经典力学

ChemRxiv Pub Date : 2024-09-19 DOI: 10.26434/chemrxiv-2024-35kds-v4

Henmei, Ni

{"title":"From new thermodynamics to classical mechanics","authors":"Henmei, Ni","doi":"10.26434/chemrxiv-2024-35kds-v4","DOIUrl":"https://doi.org/10.26434/chemrxiv-2024-35kds-v4","url":null,"abstract":"The laws of classical mechanics are rebuilt in the frame of new thermodynamics. Heat is the sum of kinetic energy, system work, and system potential of gas, while force is the linear gradients of heat variation. Exporters and importers of force are evident in terms of exotherm and endotherm. Temperature and volume gradients create asymmetric forces driving rotation and spin (self-rotation). It verifies that force transfer doesn’t need a medium. As an outstanding achievement, a brief and general equation is derived to predict the equilibrium distance of molecular interaction: L_e=∛((3π^(α-1) M_A g)/(4N_A kT)), without using any assumption, such as van der Waals force and dispersion forces. In addition, the origins and attributes of repulsion and attraction are disclosed. Predicting results is applausive. For example, at 298 K, Le for N2, O2, and CH4 are 3.11, 3.11, and 3.68 Å, comparable to the data adopted in MD simulations of the literature. Furthermore, the relationship between electricity and mass is established. An electron is characterized as a particle with a large α dependent on the interaction distance. Two electrons are mutually attractive from a distance depending on temperature. The electromagnetic phenomena are integrated.","PeriodicalId":9813,"journal":{"name":"ChemRxiv","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142267241","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Selective Ni-Catalyzed Cross-Electrophile Coupling of Heteroaryl Chlorides and Aryl Bromides at 1:1 Substrate Ratio 杂芳基氯化物和芳基溴化物在 1:1 底物比下的选择性 Ni- 催化交叉亲电偶联

ChemRxiv Pub Date : 2024-09-19 DOI: 10.26434/chemrxiv-2024-3q21n

Shannon, Stahl, Zhi-Ming, Su, Darren L., Poole, Mohammad, Rafiee, Robert S., Paton, Daniel J., Weix

引用次数: 0

Analysis of Hydrophobicity in Micropores of Metal-Organic Framework Materials 金属有机框架材料微孔中的疏水性分析

ChemRxiv Pub Date : 2024-09-19 DOI: 10.26434/chemrxiv-2024-h1x6w

Steven William, Rutherford

{"title":"Analysis of Hydrophobicity in Micropores of Metal-Organic Framework Materials","authors":"Steven William, Rutherford","doi":"10.26434/chemrxiv-2024-h1x6w","DOIUrl":"https://doi.org/10.26434/chemrxiv-2024-h1x6w","url":null,"abstract":"Water molecules in hydrophobic micropores of Metal Organic Framework (MOF) materials show disparate behavior in adsorption equilibrium. Ranging from behavior indicative of large, Type V uptakes occurring at low relative pressure, to Type III equilibrium where little water is adsorbed, this phenomenon provides a challenge for a priori prediction. In an effort to elucidate adsorption mechanisms, this study advances a quantitative description of hydrophobicity through novel application of Ising model analysis (IMA). It is applied to scrutinize hydrophobicity indicated by Type III adsorption and displayed by micropores that are too large to induce a Type V water adsorption equilibrium. Two types of hydrophobicity are identified and partitioned into structural hydrophobicity and surface hydrophobicity. Additionally, through analysis of a data set for 25 materials, the utility of the concepts of nanocapillarity and nanowetting in a modified Kelvin analysis (MKA) are established for water in MOF systems. The method and analysis are applied to these phenomena in MOF micropores and could foreseeably aid in screening studies, be used to assess the presence of cooperative, wetting, and condensation-like mechanisms and be further employed to assess hydrophobicity in other microporous materials.","PeriodicalId":9813,"journal":{"name":"ChemRxiv","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142267372","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Unusual Confinement-Induced Basicity and Proton-Mediated CH Activity of an Adipic Acid-Ammonium Cluster 己二酸-铵簇异常封闭诱导的碱性和质子介导的 CH 活性

ChemRxiv Pub Date : 2024-09-19 DOI: 10.26434/chemrxiv-2022-xqj08-v3

Christopher, Johnson, John, Kreinbihl, Nicoline, Frederiks, Kathleen, Nickson, Emily, Racow, Melanie, Chiu, Annapoorani, Hariharan

{"title":"Unusual Confinement-Induced Basicity and Proton-Mediated CH Activity of an Adipic Acid-Ammonium Cluster","authors":"Christopher, Johnson, John, Kreinbihl, Nicoline, Frederiks, Kathleen, Nickson, Emily, Racow, Melanie, Chiu, Annapoorani, Hariharan","doi":"10.26434/chemrxiv-2022-xqj08-v3","DOIUrl":"https://doi.org/10.26434/chemrxiv-2022-xqj08-v3","url":null,"abstract":"Organic acids play an important role in atmospheric chemistry, particularly in the formation of aerosol particles. They are often detected with hydronium, ammonium, or nitrate chemical ionization sources, which are generally soft ionization sources but may cause fragmentation. Here we explore the reactivity of adipic acid, an analogue to the alpha-pinene oxidation product pinic acid, upon complexation with ammonium. Mass spectra and mass-selective vibrational spectra show that even mild activation, consistent with normal operation of an electrospray ionization source, yields (adipic acid)H+ and neutral ammonia. This is traced to a specific structural motif in which both protonated carboxylic acid carbonyl groups combine to form a site that is locally more basic than ammonia. Further mild collisional activation yields sequential loss of two water molecules, the known behavior of carboxylic acids in superacids, necessitating abstraction of at least one hydrogen from a CH group. Deuterium labeling experiments confirm that the second step indeed involves CH hydrogen atoms. Comparison of vibrational spectra and quantum chemical calculations allows us to assign structures for each step, identifying several ring structures but notably not forming the minimum energy structure upon the first loss of water. ESI of a range of linear dicarboxylic acids shows this to be a common feature of this class of organic acids. We propose a mechanism that explains this reactivity and discuss possible atmospheric implications of these observations.","PeriodicalId":9813,"journal":{"name":"ChemRxiv","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142267240","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0