Hasil untuk "Organic chemistry"

L. Domingo, M. Ríos‐Gutiérrez, P. Pérez

Theoretical reactivity indices based on the conceptual Density Functional Theory (DFT) have become a powerful tool for the semiquantitative study of organic reactivity. A large number of reactivity indices have been proposed in the literature. Herein, global quantities like the electronic chemical potential μ, the electrophilicity ω and the nucleophilicity N indices, and local condensed indices like the electrophilic Pk+ and nucleophilic Pk− Parr functions, as the most relevant indices for the study of organic reactivity, are discussed.

R. Chinchilla, C. Nájera

J. W. Cook

J. Pignatello, E. Oliveros, Allison A. MacKay

A. E. Black, E. Deci

M. Eddaoudi, David B. Moler, Hailian Li et al.

Laura Buglioni, Fabian Raymenants, Aidan Slattery et al.

Photoinduced chemical transformations have received in recent years a tremendous amount of attention, providing a plethora of opportunities to synthetic organic chemists. However, performing a photochemical transformation can be quite a challenge because of various issues related to the delivery of photons. These challenges have barred the widespread adoption of photochemical steps in the chemical industry. However, in the past decade, several technological innovations have led to more reproducible, selective, and scalable photoinduced reactions. Herein, we provide a comprehensive overview of these exciting technological advances, including flow chemistry, high-throughput experimentation, reactor design and scale-up, and the combination of photo- and electro-chemistry.

Weidong Fan, Xiurong Zhang, Zixi Kang et al.

C. Stephenson, T. Yoon, D. MacMillan

Zhijie Chen, Kent O. Kirlikovali, Peng Li et al.

ConspectusCurrent global crises related to clean energy and the environment entail the development of materials that are capable of addressing these challenges. Metal-organic frameworks (MOFs), a class of functional materials assembled from metal-containing nodes and organic ligands via coordination bonds, have been successfully developed for various applications, including catalysis, toxic chemical removal, and gas storage and separation, as a result of their highly tailorable nature and precisely engineered pore structures. In particular, the exceptionally high surface areas and porosities of MOFs are two of their most attractive characteristics and place them among the best porous materials for the storage of clean energy gases, such as hydrogen and methane. Reticular chemistry stands out as a prominent approach to the design of MOFs as this strategy allows for the rational top-down design of frameworks guided by topological nets to afford extended framework structures with precise architectural arrangements at the molecular level. Bridging the gap between reticular chemistry design strategies and highly porous MOFs can facilitate the development of next-generation high-performance materials through state-of-the-art chemical design.In this Account, we summarize our group's efforts over the past few years toward the synthesis and applications of highly porous MOFs inspired by reticular chemistry. First, we describe how we leveraged reticular chemistry to synthesize NU-1500, which is based on the 6-connected edge-transitive acs net, from the assembly of triptycene-based ligands and high-valent metal trimers. This delicate design is amenable to isoreticular expansion, and including an additional phenyl group in the rigid triptycene-based ligand of NU-1500 yields NU-1501. Importantly, NU-1501-Al exhibits both a high gravimetric Brunauer-Emmett-Teller (BET) area of 7310 m2 g-1, which is the current record after satisfying the four BET consistency criteria, and a volumetric BET area of 2060 m2 cm-3. The high porosity and surface area place NU-1501 among the most promising adsorbents for the storage of methane and hydrogen. Second, we illustrate the rational synthesis of highly porous and stable Zr-MOFs based on edge-transitive nets: (1) the successful isoreticular expansions of NU-1000 (a 4,8-connected csq net) form hierarchical mesoporous MOFs with pore sizes of up to 6.7 nm; (2) the assembly of Zr6 clusters and tetracarboxylates yields the NU-1100 series (4,12-connected ftw net) with BET areas of 4300-6500 m2 g-1; and (3) the use of hexacarboxylates in combination with Zr6 clusters results in the formation of the NU-1600 series (a 6,12-connected alb net) with BET areas of 2000-4500 m2 g-1. Third, we leveraged a reticular exploration strategy to access mesoporous uranium-based MOFs, NU-1300 (a 3,4-connected tbo net, 2100 m2 g-1) and NU-1301 (a 3-connected nun net, 4750 m2 g-1). In particular, we investigated the structurally complex NU-1301, which formed serendipitously from the combination of uranyl clusters and triangular carboxylates to afford a structure with the largest unit cell among all reported MOFs.Finally, we provide an overview of potential applications of these highly porous MOFs, including water capture, catalysis, methane storage, hydrogen storage, and the separation of organic dyes and biological macromolecules. We hope that this Account may serve as a blueprint and stimulate researchers to develop the next generation of highly porous materials for energy- and environment-related applications and beyond.

D. Pletcher, R. Green, Richard C. D. Brown

Electrosynthesis has much to offer to the synthetic organic chemist. But in order to be widely accepted as a routine procedure in an organic synthesis laboratory, electrosynthesis needs to be presented in a much more user-friendly way. The literature is largely based on electrolysis in a glass beaker or H-cells that often give poor performance for synthesis with a very slow rate of conversion and, often, low selectivity and reproducibility. Flow cells can lead to much improved performance. Electrolysis is participating in the trend toward continuous flow synthesis, and this has led to a number of innovations in flow cell design that make possible selective syntheses with high conversion of reactant to product with a single passage of the reactant solution through the cell. In addition, the needs of the synthetic organic chemist can often be met by flow cells operating with recycle of the reactant solution. These cells give a high rate of product formation while the reactant concentration is high, but they perform best at low conversion. Both approaches are considered in this review and the important features of each cell design are discussed. Throughout, the application of the cell designs is illustrated with syntheses that have been reported.

Kate Lauder, A. Toscani, Nicolò Scalacci et al.

M. Gaillard, A. Faure, P. Hily-Blant et al.

The spatial distribution of the chemical reservoirs in protoplanetary disks is key to elucidate the composition of planets, especially habitable ones. However, the partitioning of the main elements among the refractory and volatile phases is still elusive. Key parameters such as the carbon-to-oxygen C/O elemental ratio and the ionization fraction remain poorly constrained, with the latter potentially orders of magnitude lower than in the interstellar medium. Moreover, the thermal structure of the gas is also poorly known, despite its deep influence on gas-phase chemistry. In this context, ortho-to-para ratios could provide selective and sensitive probes. Recent ALMA observations have measured the spatially resolved column density of ortho-and para-H2CO in the transition disk orbiting TW Hya and derived the radial profile of the ortho-to-para ratio. Yet, current disk models do not include the nuclear-spin-resolved chemistry required to interpret these observations. The present work aims to fill this gap, by combining a parametric disk physical model of TW Hya with the UGAN network, updated to include a comprehensive description of the nuclear-spin-resolved chemistry of formaldehyde. This new model reproduces the observed column density of H2CO to within a factor of 2, as well as the measured ortho-to-para ratio which varies from 1.5 in the outer disk to 3 inside 90au. In particular the low value of this ratio beyond 90au is well explained by our model. However, the statistical value of 3 measured below 70au cannot be reproduced, suggesting that additional processes involving ices may be involved. Our parameter space exploration shows that the abundance of H2CO is highly sensitive to the C/O elemental ratio and to the cosmic-ray ionization rate. Future observations of ortho-and para-H2CO, based on well selected rotational transitions, in a large sample of disks, appear highly desirable.

Rita Patrizia Aquino, Teresa Mencherini, Pierluigi Mazzei et al.

This study reports on the development of a carbohydrate-based spray-dried microparticulate system (F-CHES) conceived for the stabilization and foliar delivery of polyphenol-rich plant extracts for sustainable phyto defense applications. Chestnut spiny bur (CHES) extract, with demonstrated anti-fungal activity against phytopathogens, was micro-encapsulated via spray-drying in a polysaccharide matrix, composed primarily of inulin (INU DP ∼15), sodium carboxymethylcellulose (CMC) and low amount of sodium lauryl sulfate (SLS 0.05 % w/v), engineered to improve extract processability, water compatibility, stability and functional performance. Structural characterization by semi-solid (HRMAS) and solid-state (CPMAS) NMR revealed polysaccharide matrix–extract interactions that influenced the internal organization and component distribution within microparticles. The integration of high-resolution analytical techniques was also essential for standardizing the production process. The optimized F-CHES 0.8 micropowder, containing 1.5 % w/v of CHES extract, 5 % INU, 0.8 % Na-CMC, showed a process yield (70.42 ± 2.42 %) and high encapsulation efficiency (98.58 %). The formulation ensured chemical stability over 12 weeks (active compound retention ≥94.86 %), and displayed favorable morphological and physicochemical properties, including hydrodynamic diameter of 0.55 µm and ζ-potential of –37.2 mV. Interestingly, upon dispersion in water, the microparticles converted into a colloidal state and the resulting dispersion can form stable transparent coating on leaf surface suited for foliar delivery.

Furkan Şahin

Microbial contamination poses a significant challenge to the management of water resources and biomedical applications. In this study, the development of a biogenic antimicrobial filtration system has been successfully achieved. This system utilizes a plant extract-mediated synthesis approach for in situ formation of silver nanoparticles (AgNPs) within a porous sponge matrix. The fabrication process involved the immersion of a commercial sponge in an aqueous solution of AgNO3 and plant extract, followed by a thermal treatment. The structural and chemical properties of the Ag@Sponge were then confirmed via a range of analytical methods, including scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). These results indicated the successful incorporation of AgNPs within the sponge, with a predominant spherical morphology and an average size of 54 ± 14 nm. Antimicrobial activity tests demonstrated that Ag@Sponge exhibited significant bacterial and fungal inactivation, achieving >99.99999% microbial reduction against Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), and Candida albicans (C. albicans) (R > 7). Furthermore, the results of filtration experiments demonstrated that microbial removal efficiency increased progressively over six cycles, reaching final reductions of 6.2–6.4 log CFU/mL for E. coli, S. aureus, and C. albicans. Mechanical durability tests confirmed that Ag@Sponge retained >6 log CFU/mL reduction after 5000 cm abrasion (down to 6.6 ± 0.5) and 400 bending cycles (down to 6.1 ± 1.2), indicating strong mechanical resilience and in situ nanoparticle stability. These findings highlight the potential of Ag@Sponge as a sustainable and efficient antimicrobial filtration material for practical applications in water purification and medical decontamination.

Yu Zhang, Yang Han, Shuai Chen et al.

Chemical synthesis, as a foundational methodology in the creation of transformative molecules, exerts substantial influence across diverse sectors from life sciences to materials and energy. Current chemical synthesis practices emphasize laborious and costly trial-and-error workflows, underscoring the urgent need for advanced AI assistants. Nowadays, large language models (LLMs), typified by GPT-4, have been introduced as an efficient tool to facilitate scientific research. Here, we present Chemma, a fully fine-tuned LLM with 1.28 million pairs of Q&A about reactions, as an assistant to accelerate organic chemistry synthesis. Chemma surpasses the best-known results in multiple chemical tasks, e.g., single-step retrosynthesis and yield prediction, which highlights the potential of general AI for organic chemistry. Via predicting yields across the experimental reaction space, Chemma significantly improves the reaction exploration capability of Bayesian optimization. More importantly, integrated in an active learning framework, Chemma exhibits advanced potential for autonomous experimental exploration and optimization in open reaction spaces. For an unreported Suzuki-Miyaura cross-coupling reaction of cyclic aminoboronates and aryl halides for the synthesis of $α$-Aryl N-heterocycles, the human-AI collaboration successfully explored suitable ligand and solvent (1,4-dioxane) within only 15 runs, achieving an isolated yield of 67%. These results reveal that, without quantum-chemical calculations, Chemma can comprehend and extract chemical insights from reaction data, in a manner akin to human experts. This work opens avenues for accelerating organic chemistry synthesis with adapted large language models.

Md. Makshuder Rahman Zim, Nurnabi Ahmed, Mostak Ahmed et al.

Bovine anaplasmosis is an infectious, tick-borne disease caused by Anaplasma species, which is accountable for huge economic loss in dairy industry. This study was aimed to determine the seroprevalence of bovine anaplasmosis on randomly selected 61 commercial dairy farms in 3 intensive regions of Bangladesh. A total of 1472 sera were analysed using VMRD Anaplasma Antibody Test Kit cELISA v2 for the presence of Anaplasma-specific antibodies. The highest regional seroprevalence of Anaplasma was 45.93% in individual level and 74.4% in herd level recorded in the southeast region, whereas it was 48.8% in individual level and 83.3% in herd level in Khagrachari and Sherpur districts, indicating an emerging state of the disease. The herd size and type in herd level and regions, districts, sex, age and breed in individual level were significantly (P ≤ 0.05) associated with anaplasmosis. Multivariate logistic regression analysis showed that cattle aged >1 year had 1.86 times higher odds compared to cattle younger than 1 year. Dairy cows had the highest odds (2.25) of anaplasmosis, followed by dairy heifers (1.68), compared to bulls. Compared to herd sizes of <4, the odds of Anaplasma infection were 11.3 and 7.45 times greater in herd sizes of >28 and 4–28. Crossbred cattle had 2.4 times higher odds of anaplasmosis compared to indigenous cattle. This first seroprevalence study signifies the widespread presence and underscores the importance of monitoring and managing anaplasmosis to safeguard cattle health in Bangladesh. Study on the molecular epidemiology and genetic diversity of Anaplasma among cattle populations should be prioritized.

Husson Ara, Nasreen Naz, Ayesha Walid et al.

Background: Adenomyosis is an important benign gynecological condition among females with variable signs and symptoms. Prompt detection of suspicious cases is important for the effective management of the disease. The objective of the current study was to determine the frequency of adenomyosis on transvaginal ultrasound (TVS), its diagnostic accuracy, and the identification of associated factors in women with symptoms of adenomyosis. Methods: This cross-sectional study was carried out at the radiology department of Dow University Hospital, Karachi, Pakistan from January 2022 to March 2023. All married females of reproductive age group presented with symptoms of adenomyosis for more than 7 days were included. Adenomyosis on TVS and histopathology were noted. Moreover, associated factors of adenomyosis were also studied. Results: Of 280 patients, adenomyosis on TVS was observed in 180 (64.3%) patients whereas on histopathology in 176 (62.9%) patients.  Diagnostic accuracy of adenomyosis on TVS showed that sensitivity was 89.20%, specificity 77.88%, positive predicted value 87.22%, negative predicted value 81.00%, and accuracy was found to be 85.00%. A significantly higher proportion of adenomyosis was observed among women who had infertility (p<0.001), symptoms of dysmenorrhea (p <0.001), dyspareunia (p<0.002), urinary symptoms (p <0.001), and GI symptoms (p<0.001). Conclusion: TVS is a valuable imaging modality for identifying adenomyosis, especially in patients with clinical symptoms. Furthermore, there is a significant association between adenomyosis and various clinical symptoms, including infertility, dysmenorrhea, dyspareunia, urinary symptoms, and gastrointestinal symptoms.

Zinnat Shahina, Tanya E. S. Dahms

<i>Candida albicans</i> is an emerging multidrug-resistant opportunistic pathogen that causes candidiasis, superficial infections on the mucosa, nails or skin, and life-threatening candidemia in deep tissue when disseminated through the bloodstream. Recently, there has been a sharp rise in resistant strains, posing a considerable clinical challenge for the treatment of candidiasis. There has been a resurged interest in the pharmacological properties of essential oils and their active components, for example, monoterpenes with alcohol (-OH) and aldehyde (-CHO) groups. Eugenol and citral have shown promising in vitro and in vivo activity against <i>Candida</i> species. Although there is substantial research on the efficacy of these essential oil components against <i>C. albicans</i>, a detailed knowledge of their mycological mechanisms is lacking. To explore the broad-spectrum effects of EOs, it is more meaningful and rational to study the whole essential oil, along with some of its major components. This review provides a comprehensive overview of eugenol and citral anticandidal and antivirulence activity, alone and together, along with the associated mechanisms and limitations of our current knowledge.

Juris Kalvans, Juris Freimanis

Context. Dust grains in circumstellar envelopes are likely to have a spread-out temperature distribution. Aims. To investigate how trends in temperature distribution between small and large grains affect the hot corino chemistry of complex organic molecules (COMs) and warm carbon-chain chemistry (WCCC). Methods. A multi-grain multi-layer astrochemical code with an up-to-date treatment of surface chemistry was used with three grain temperature trends: grain temperature proportional to grain radius to the power -1/6 (Model M-1/6), to 0 (M0), and to 1/6 (M1/6). The cases of hot corino and WCCC chemistry were investigated, for a total of six models. The essence of these changes is for the main ice reservoir - small grains - having higher (M-1/6) or lower (M1/6) temperature than the surrounding gas. Results. The chemistry of COMs shows better agreement with observations in models M-1/6 and M1/6 than in Model M0. Model M-1/6 shows best agreement for WCCC because earlier mass-evaporation of methane ice from small grains induces the WCCC phenomenon at lower temperatures. Conclusions. Models considering several grain populations with different temperatures can more precisely reproduce circumstellar chemistry.