Hasil untuk "Organic chemistry"

M. Bandini, A. Eichholzer

G. Aromí, L. Barrios, O. Roubeau et al.

W. Pryor

E. Anglin, Lingyun Cheng, W. Freeman et al.

E. Merritt, B. Olofsson

A. Hounslow

F. Perna, P. Vitale, V. Capriati

Several examples illustrate the effectiveness of using Deep Eutectic Solvents (DESs) as environmentally responsible reaction media in polar organometallic chemistry and in metal-catalysed and biocatalysed processes in place of conventional, often hazardous volatile organic compounds (VOCs). Apart from the standpoint of ‘greenness’, applications of DESs in the aforementioned fields also reveal novel aspects of reactivity of practical significance, which are worthy of an in-depth mechanistic understanding: (a) metal-mediated organic transformations can be run in DESs competitively with protonolysis, often at room temperature and under air, (b) metal-catalysed reactions proceed efficiently and under milder conditions in DESs than in VOCs, with the catalyst and DES being easily and successfully recycled and (c) biocatalysts often exhibit higher stability, selectivity and performances in DES mixtures than in aqueous solutions, as well as a somewhat intriguing stereoselectivity.

P. Devi, U. Das, A. Dalai

Z. Wicks, F. Jones, S. Pappas et al.

K. H. Tan

I. Beletskaya, F. Alonso, V. Tyurin

Abstract Synthetic organic chemistry experienced a significant advance in the last quarter of the 20th century with the advent of the transition-metal catalyzed cross-coupling reactions. The utility of these reactions was universally acknowledged and expressed in the Chemistry Nobel prize awarded to professors Heck, Suzuki and Negishi in 2010. In this scenario, the discovery of the Suzuki-Miyaura reaction was a landmark that occupies a privileged position because of its versatility, compatibility and pivotal contribution to diverse disciplines, including materials science and drug discovery. Despite the substantial progress attained for this reaction until 2010, there is still room for improvement, particularly, if we are concerned about the health of the Earth and aware of the paramount importance to produce substances under the guidelines of sustainable and Green Chemistry. In the present review, we summarize the efforts devoted by a wide and specialized scientific community to upgrade the Suzuki-Miyaura reaction during the post-Nobel prize period. An overview covering new catalytic systems, methods and conditions is provided, together with some applications and updated mechanistic viewpoints.

Daniela M. Arias-Rotondo, J. McCusker

Rory C. McAtee, E. McClain, C. Stephenson

Over the past decade, photoredox catalysis has risen to the forefront of synthetic organic chemistry as an indispensable tool for selective small-molecule activation and chemical-bond formation. This cutting-edge platform allows photosensitizers to convert visible light into chemical energy prompting generation of reactive radical intermediates. In this Review, we highlight some of the recent key contributions in the field, including: the impact of the chosen light arrays; promoting fundamental cross-coupling steps; selectively functionalizing aliphatic amines; engaging complementary mechanistic paradigms; and applications in industry. With such a wide breadth of reactivity already realized, the presence of photoredox catalysis in all sectors of organic chemistry is expected for years to come.

Christopher G. Jones, M. Martynowycz, J. Hattne et al.

In the many scientific endeavors that are driven by organic chemistry, unambiguous identification of small molecules is of paramount importance. Over the past 50 years, NMR and other powerful spectroscopic techniques have been developed to address this challenge. While almost all of these techniques rely on inference of connectivity, the unambiguous determination of a small molecule’s structure requires X-ray and/or neutron diffraction studies. In practice, however, X-ray crystallography is rarely applied in routine organic chemistry due to intrinsic limitations of both the analytes and the technique. Here we report the use of the electron cryo-microscopy (cryoEM) method microcrystal electron diffraction (MicroED) to provide routine and unambiguous structural determination of small organic molecules. From simple powders, with minimal sample preparation, we could collect high-quality MicroED data from nanocrystals (∼100 nm, ∼10–15 g) resulting in atomic resolution (<1 Å) crystal structures in minutes.

P. Grieco

Deepu Murukadas, Dahyeon Park, Minjae Kim et al.

Abstract Achieving high-performance sodium-based solid-state electrolytes (SSEs) through environmentally friendly processes is crucial to establishing a solid foundation for safe and inexpensive energy storage devices. Here we demonstrate nonflammable sodium cation-transporting SSEs prepared from aqueous solutions of branched poly(ethylene imine) (bPEI), sodium hydroxide (NaOH), and sodium hexametaphosphate (SHMP). The bPEI:NaOH:SHMP (PNaS) SSEs exhibited an outstanding ion conductivity of ~1 mS/cm at SHMP = 20 mol%, which is 5 times higher than 0.18 mS/cm for the bPEI:NaOH (PNa) SSEs, due to the SHMP-induced morphology optimization for efficient Na+ transport. The optimum PNaS SSEs could deliver the output voltage of 4.4 V by galvanostatic charging at 0.5 mA/g, exhibiting long-term retention characteristics (>1000 s). The PNaS supercapacitors exhibited stable operation with 99.68% capacitance retained during 2000 charging/discharging cycles, while the PNaS films were considerably stable without burning upon the flammability test.

A. Marshall, R. Rodgers

Elettra Savigni, Elisa Girometti, Laura Sisti et al.

The removal of pharmaceutical contaminants like the anticonvulsant carbamazepine (CBZ) from water sources is a growing environmental challenge. This study explores the development of molecularly imprinted polymers (MIPs) tailored for CBZ adsorption using a bulk polymerization approach. Initially, this study focused on selecting the optimal cross-linker, comparing a trifunctional (trimethylolpropane triacrylate, TRIM) and a bifunctional cross-linker (ethylene glycol dimethacrylate, EGDMA) in combination with two common monomers (2-vinylpyridine and methacrylic acid). TRIM-based MIPs demonstrated superior adsorption efficiency and stability due to their higher cross-linking density. To improve sustainability, six bio-based monomers were investigated; of these, eugenol (EUG) and coumaric acid (COU) showed the best CBZ affinity due to π-π interactions and hydrogen bonding. Adsorption tests conducted in pharmaceutical-spiked real wastewater demonstrated that MIPs exhibit a high selectivity for CBZ over other pharmaceuticals like the anti-inflammatory drugs diclofenac (DCF) and ibuprofen (IBU), even at high concentrations. Reaction conditions were further optimized by adjusting the reaction time and the ratio between reagents to enhance selectivity and adsorption performance. These results highlight the potential of bio-based MIPs as efficient and selective materials for the removal of pharmaceutical pollutants from wastewater.

Katarzyna Szramowiat-Sala, Marta Marczak-Grzesik, Mateusz Karczewski et al.

Abstract Polycyclic aromatic hydrocarbons (PAHs) are hazardous air pollutants with well-documented carcinogenic, mutagenic, and toxic effects. This study investigates the chemical composition and sources of PAHs in Kraków, a city characterized by diverse air quality challenges. PM10 and PM2.5 samples were collected during the winter seasons of 2014 and 2015, enabling a detailed assessment of PAH concentrations and their atmospheric transformations. The results indicate that PAH levels frequently exceeded European Union and World Health Organization limits, with benzo[a]pyrene (BaP) reaching peak concentrations of 38.8 ng m−3 in PM10 and 30.2 ng m−3 in PM2.5, highlighting significant health risks. To determine PAH sources, a chemical-based framework integrating diagnostic ratios, receptor modeling, and backward trajectory analysis was applied. The findings reveal that coal and biomass combustion were dominant PAH contributors, with additional influences from vehicular emissions and industrial activities. The BaP/(BaP + BeP) ratio suggested that PAHs in PM2.5 underwent more atmospheric aging than those in PM10, indicating that finer particles play a crucial role in PAH transport and transformation. Furthermore, correlations with inorganic and organic PM constituents, such as chloride and levoglucosan, underscored the mixed influence of fossil fuel and biomass burning. The study also evaluated the toxicological implications of PAHs, demonstrating that mutagenic activity exceeded toxicity levels, and finer particles posed a greater carcinogenic risk. While the exposure index suggested that short-term exposure remained within acceptable limits, long-term effects require further assessment. Given the complex interplay of emission sources and atmospheric processes, continuous monitoring and targeted mitigation strategies are essential for improving urban air quality.

Moon-Sub Lee, Nusrat Jahan Methela, Gun-Ho Lee et al.

Nitric oxide (NO) and melatonin (MT) significantly influence photosynthetic processes by modulating redox homeostasis, chlorophyll content, stomatal conductance, and gene expression, particularly under abiotic stress conditions. This review summarizes the intricate crosstalk between NO and melatonin, focusing on their coordinated roles in regulating photosynthetic efficiency. Evidence from various plant species indicates that the application of exogenous NO and melatonin enhances chlorophyll content, photosystem efficiency (particularly PSII), and photosynthetic performance, mitigating stress-induced damage. Molecular analysis demonstrates that both molecules influence key photosynthetic gene modulating photosystems I and II, and Calvin cycle activities. Moreover, NO and melatonin collaboratively regulate stomatal movements through ABA, Ca²⁺, and H₂O₂ signaling pathways, involving genes such as <i>PMRT1</i>, <i>CIPKs</i>, and <i>OST1</i>. Experimental data from diverse plant species under stress conditions, including drought, salinity, heavy metals, and flooding, highlight their synergistic protective effects. Exploring these mechanisms further may enable practical agricultural strategies involving combined NO and melatonin treatments to improve crop resilience and productivity under increasingly challenging environmental conditions. Future research directions should emphasize unraveling detailed molecular interactions, enabling targeted biotechnological applications in crop improvement programs for enhanced global food security.