Role In Chemistry Research Articles

Modifying Woodward-Hoffmann Stereoselectivity Under Vibrational Strong Coupling.

Vibrational strong coupling (VSC) has recently been shown to change the rate and chemoselectivity of ground‐state chemical reactions via the formation of light–matter hybrid polaritonic states. However, the observation that vibrational‐mode symmetry has a large influence on charge‐transfer reactions under VSC suggests that symmetry considerations could be used to control other types of chemical selectivity through VSC. Here, we show that VSC influences the stereoselectivity of the thermal electrocyclic ring opening of a cyclobutene derivative, a reaction which follows the Woodward–Hoffmann rules. The direction of the change in stereoselectivity depends on the vibrational mode that is coupled, as do changes in rate and reaction thermodynamics. These results on pericyclic reactions confirm that symmetry plays a key role in chemistry under VSC.

Role of chemistry in drug discovery and drug design

The drug discovery and development process use as target of new drug. This process transform some techniques such as screening, optimization, characterization, validation, synthesis. Target based drug design is more important, long-term, successful process. Which is use as high Throughput screening (HTS). Target is synthesized by combination of chemistry. All type of chemistry use in new drug discovery such as analytical chemistry, computational chemistry, organic chemistry, inorganic chemistry, medicinal chemistry, physical chemistry, biochemistry etc. Analytical chemistry in pharmaceutical drug development providing assurance of the quality, safety and efficacy of new drug. Analytical chemistry play and important in developing a new drug. HPLC is most important Analytical process in pharmaceutical industry, other techniques are also used. It’s used as investigate polymorphism in new drug. All drugs are manufacturing under GMP i.e Good manufacturing practices. 50% Analytical chemistry used in drug discovery and development. Analytical method and instrumentation is used in the preclinical testing, toxicity testing and quality control. Commonly used as purification chemistry.

The Role of Chemistry and Scientists

The Role of Chemistry and Scientists

Playing with the weakest supramolecular interactions in a 3D crystalline hexakis[60]fullerene induces control over hydrogenation selectivity.

Weak forces can play an essential role in chemical reactions. Controlling such subtle forces in reorganization processes by applying thermal or chemical stimuli represents a novel synthetic strategy and one of the main targets in supramolecular chemistry. Actually, to separate the different supramolecular contributions to the stability of the 3D assemblies is still a major challenge. Therefore, a clear differentiation of these contributions would help in understanding the intrinsic nature as well as the chemical reactivity of supramolecular ensembles. In the present work, a controlled reorganization of an hexakis[60]fullerene-based molecular compound purely governed by the weakest van der Waals interactions known, i.e. the dihydrogen interaction – usually called sticky fingers – is illustrated. This pre-reorganization of the hexakis[60]fullerene under mild conditions allows a further selective hydrogenation of the crystalline material via hydrazine vapors exposure. This unique two-step transformation process is monitored by single-crystal to single-crystal diffraction (SCSC) which allows the direct observation of the molecular movements in the lattice and the subsequent solid–gas hydrogenation reaction.

Extension of bridge graphs and their chemical applications

Abstract A topological invariant is a numerical value which can be associated with a graph structure. These graph invariants are utilized for modeling information of molecules in structural chemistry and biology. Over the years many topological indices are proposed and studied based on degree, distance and other parameters of graph. Also graph invariants play a significant role in chemistry, especially, QSPR/QSAR studies. In this paper, we concentrate two graph invariants such as augmented Zagreb invariant and inverse sum indeg invariant of extended bridge graphs.

On the Effect of the Various Assumptions and Approximations used in Molecular Simulations on the Properties of Bio-Molecular Systems: Overview and Perspective on Issues.

Computer simulations of molecular systems enable structure-energy-function relationships of molecular processes to be described at the sub-atomic, atomic, supra-atomic or supra-molecular level and plays an increasingly important role in chemistry, biology and physics. To interpret the results of such simulations appropriately, the degree of uncertainty and potential errors affecting the calculated properties must be considered. Uncertainty and errors arise from (1) assumptions underlying the molecular model, force field and simulation algorithms, (2) approximations implicit in the interatomic interaction function (force field), or when integrating the equations of motion, (3) the chosen values of the parameters that determine the accuracy of the approximations used, and (4) the nature of the system and the property of interest. In this overview, advantages and shortcomings of assumptions and approximations commonly used when simulating bio-molecular systems are considered. What the developers of bio-molecular force fields and simulation software can do to facilitate and broaden research involving bio-molecular simulations is also discussed.

Solvated Electrons in Solids-Ferroelectric Large Polarons in Lead Halide Perovskites.

Solvation plays a pivotal role in chemistry and biology. A solid-state analogy of solvation is polaron formation, but the magnitude of Coulomb screening is typically an order of magnitude weaker than that of solvation in aqueous solutions. Here, we describe a new class of polarons, the ferroelectric large polaron, proposed initially by Miyata and Zhu in 2018 (Miyata, K.; Zhu, X.-Y. Ferroelectric Large Polarons. Nat. Mater. 2018, 17 (5), 379-381). This type of polaron allows efficient Coulomb screening of an electron or hole by extended ordering of dipoles from symmetry-broken unit cells. The local ordering is reflected in the ferroelectric-like THz dielectric responses of lead halide perovskites (LHPs) and may be partially responsible for their exceptional optoelectronic performances. Despite the likely absence of long-range ferroelectricity in LHPs, a charge carrier may be localized to and/or induce the formation of nanoscale domain boundaries of locally ordered dipoles. Based on the known planar nature of energetically favorable domain boundaries in ferroelectric materials, we propose that a ferroelectric polaron localizes to planar boundaries of transient polar nanodomains. This proposal is supported by dynamic simulations showing sheet-like transient electron or hole wave functions in LHPs. Thus, the Belgian-waffle-shaped ferroelectric polaron in the three-dimensional LHP crystal structure is a large polaron in two dimensions and a small polaron in the perpendicular direction. The ferroelectric large polaron may form in other crystalline solids characterized by dynamic symmetry breaking and polar fluctuations. We suggest that the ability to form ferroelectric large polarons can be a general principle for the efficient screening of charge carriers from scattering with other charge carriers, with charged defects and with longitudinal optical phonons, thus contributing to enhanced optoelectronic properties.

Growth, collaboration, and advocacy

Most of us in the chemistry enterprise appreciate the beneficial role of chemistry in our society. Chemistry provides employment to a lot of people in academia, industry, government, and nonprofit ...

Arctic ozone depletion in 2019/20: Roles of chemistry, dynamics and the Montreal Protocol

Arctic ozone depletion in 2019/20: Roles of chemistry, dynamics and the Montreal Protocol

Ligand-induced chirality and optical activity in semiconductor nanocrystals: theory and applications

Abstract Chirality is one of the most fascinating occurrences in the natural world and plays a crucial role in chemistry, biochemistry, pharmacology, and medicine. Chirality has also been envisaged to play an important role in nanotechnology and particularly in nanophotonics, therefore, chiral and chiroptical active nanoparticles (NPs) have attracted a lot of interest over recent years. Optical activity can be induced in NPs in several different ways, including via the direct interaction of achiral NPs with a chiral molecule. This results in circular dichroism (CD) in the region of the intrinsic absorption of the NPs. This interaction in turn affects the optical properties of the chiral molecule. Recently, studies of induced chirality in quantum dots (QDs) has deserved special attention and this phenomenon has been explored in detail in a number of important papers. In this article, we review these important recent advances in the preparation and formation of chiral molecule–QD systems and analyze the mechanisms of induced chirality, the factors influencing CD spectra shape and the intensity of the CD, as well as the effect of QDs on chiral molecules. We also consider potential applications of these types of chiroptical QDs including sensing, bioimaging, enantioselective synthesis, circularly polarized light emitters, and spintronic devices. Finally, we highlight the problems and possibilities that can arise in research areas concerning the interaction of QDs with chiral molecules and that a mutual influence approach must be taken into account particularly in areas, such as photonics, cell imaging, pharmacology, nanomedicine and nanotoxicology.

Thermodynamics and Kinetics of Drug-Target Binding by Molecular Simulation.

Computational studies play an increasingly important role in chemistry and biophysics, mainly thanks to improvements in hardware and algorithms. In drug discovery and development, computational studies can reduce the costs and risks of bringing a new medicine to market. Computational simulations are mainly used to optimize promising new compounds by estimating their binding affinity to proteins. This is challenging due to the complexity of the simulated system. To assess the present and future value of simulation for drug discovery, we review key applications of advanced methods for sampling complex free-energy landscapes at near nonergodicity conditions and for estimating the rate coefficients of very slow processes of pharmacological interest. We outline the statistical mechanics and computational background behind this research, including methods such as steered molecular dynamics and metadynamics. We review recent applications to pharmacology and drug discovery and discuss possible guidelines for the practitioner. Recent trends in machine learning are also briefly discussed. Thanks to the rapid development of methods for characterizing and quantifying rare events, simulation’s role in drug discovery is likely to expand, making it a valuable complement to experimental and clinical approaches.

Formation of thioesters by dehydrogenative coupling of thiols and alcohols with H2 evolution

Thioesters play important roles in chemistry and biology, but their synthesis generally exhibits a poor atom economy and generates copious waste. We report here the dehydrogenative coupling of alcohols and thiols to yield thioesters and evolve H2. This waste-free reaction is catalysed by an acridine-based ruthenium pincer complex in hexamethyldisiloxane as the optimal solvent without any additives. Various thioesters were formed in good-to-excellent yields using equivalent amounts of alcohols and thiols in excellent selectivity with hydrogen gas as the only by-product. A plausible mechanism, which involves an outer-sphere dehydrogenation process in which the thiol not only serves as a reactant, but also as an assisting ligand, is proposed based on mechanistic studies and the isolation of intermediates. This system provides a facile, efficient and waste-free synthesis of thioesters. Synthetic methods for the green and atom-economical synthesis of thioesters are scarce. Now, a catalytic protocol utilizing a ruthenium pincer complex provides efficient access to thioesters with hydrogen gas as the sole by-product via dehydrogenative coupling of alcohols with thiols.

Chemistry Made Easy: Teaching Students about the Link Between Marine Chemistry and Coral Reef Biodiversity

Teaching students about chemistry can be fun. Here, students learn that chemistry is linked to all marine life and affects where they live, the community that they live in, and what eats them. Some chemicals made by organisms have negative effects on humans and marine life, and these toxins and venoms can bioaccumulate in fish and affect human consumers who rely on critical marine resources for food. After learning about the role of chemistry in this food web and how humans might be affected by contaminated seafood, students can brainstorm about ways to increase food safety whilst considering community needs in regions of the world that may have economic difficulties. This activity has modifications for the visually impaired.

Drug Development 101: A Primer.

Drug development is a term used to define the entire process of bringing a new drug or device to market. It is an integrated, multidisciplinary endeavor that includes drug discovery, chemistry and pharmacology, nonclinical safety testing, manufacturing, clinical trials, and regulatory submissions. This report summarizes presentations of a workshop entitled "Drug Development 101," held at the 39th Annual Meeting of the American College of Toxicology in West Palm Beach, Florida. The workshop was designed to provide an introductory overview of drug development. Experienced scientists from industry and government provided overviews of each area, with a focus on safety assessment, and described some of the challenges that can arise. The role of chemistry and manufacturing was discussed in the context of early- and late-stage product development and approaches to assess, control, and limit impurities. The toxicologic assessment was emphasized in early-phase development, from the selection of a candidate drug through the determination of a first-in-human starting dose. Clinical trial development was discussed in the context of regulatory requirements and expectations. The final topic of issues and considerations in the review processes of different types of submissions to Food and Drug Administration included advice for best practices in authoring good Investigational New Drug and New Drug Application/Biologic License Application submissions and interacting effectively with regulatory reviewers.

Irregularity indices for line graph of Dutch windmill graph

Among topological descriptors topological indices are significant and they have a conspicuous role in chemistry. Dutch Windmill graph Dxy can be obtain by taking x copies of cycle Cy with a vertex in common. In this paper, we will compute some irregularity índices that are useful in quantitative structure activity relationship for Line Graph of Dutch Windmill graph.

Geochemical compositional controls on DNA strand breaks induced in in vitro cell-free assays by crushed rock powders from the Panasqueira mine area, Portugal

DNA strand breaks are a common form of DNA damage that can contribute to chromosomal instability or gene mutations. Such strand breaks may be caused by exposure to heavy metals. The aim of this study was to assess the level of DNA strand breaks caused by µm-scale solid particles of known chemical composition with elevated heavy metals/metalloids, notably arsenic, using an in vitro cell-free DNA plasmid scission assay. These samples were incubated with and without H2O2 to see whether damage occurs directly or indirectly through the Fenton reaction. Levels of DNA damage in the absence of H2O2 were < 10%, but in the presence of H2O2, all samples showed higher levels of damage ranging from 10 to 100% suggesting that damage was being incurred through the Fenton reaction. Using bivariate correlation analysis and multiple linear regression, manganese oxide (MnO), sulphur (S), copper (Cu), and zinc (Zn) concentrations in the particulates were found to be the most significant predictors of DNA damage. The mechanism of this DNA damage formation has yet to be thoroughly investigated but is hypothesised to be due to reactive oxygen species formation. Further work is required to assess the extent of contribution of reactive oxygen species to this DNA damage, but this study highlights the potential role of chemistry and/or mineralogy to the extent and/or nature of DNA damage caused by particulates.

The eccentric based Zagreb indices of tetra sheets

Among topological descriptor, connectivity indices are very important and they have a prominent role in chemistry. The eccentric based Zagreb indices are defined as . In this article we compute the eccentric based Zagreb indices for an infinite families of tetra sheets equilateral triangular and rectangular.

“Greenness” in Chemistry Education – Look into Textbook Reaction Examples

Chemistry has played a dual role in the unfolding picture of global development.1 The chemical sciences have significantly improved overall quality of life but have also caused several severe environmental problems. To alter the public perception of chemistry from a “troublemaker” to a positive field necessary for global advancement, the United Nations sustainable development goals (SDGs) must be used to reposition chemistry in a broader context.2 The SDGs are just beginning to be incorporated into post-secondary chemistry education, creating the essential foundation for teaching students about the role of chemistry as the central sustainability science.3&#x0D; &#x0D; We are investigating how sustainability has been incorporated into chemistry education. The work was carried out by analyzing the organic reactions used as examples in a widely adopted organic chemistry textbook (Organic Chemistry, 2nd edition, Oxford Press). These reactions were examined using a sustainability framework consisting of several existing mass- and energy- based “green chemistry” metrics. The idea of “green chemistry” was formulated in the 1990s to address the environmental crises caused by expanding urbanization, and provides a direction chemistry must take to ensure its development is sustainable. The results of our textbook analysis create a quantitative indicator of the overall “greenness” of the content used as the basis for chemistry courses in Canada.&#x0D; &#x0D; &#x0D; Anastas, P.; Zimmerman, J. B., Chem 2016, 1 (1), 10-12.&#x0D; Matlin, S.; Mehta, G.; Hopf, H.; Krief, A., Nature Chemistry 2015, 7, 941.&#x0D; Armstrong, L. B.; Rivas, M. C.; Douskey, M. C.; Baranger, A. M., Current Opinion in Green and Sustainable Chemistry 2018, 13, 61-67.&#x0D;

Off the Beaten Path: Almost Clean Formation of Indene from the ortho-Benzyne + Allyl Reaction.

Polycyclic aromatic hydrocarbons (PAHs) play an important role in chemistry both in the terrestrial setting and in the interstellar medium. Various, albeit often inefficient, chemical mechanisms have been proposed to explain PAH formation, but few yield polycyclic hydrocarbons cleanly. Alternative and quite promising pathways have been suggested to address these shortcomings with key starting reactants including resonance stabilized radicals (RSRs) and o-benzyne. Here we report on a combined experimental and theoretical study of the reaction allyl + o-benzyne. Indene was found to be the primary product and statistical modeling predicts only 0.1% phenylallene and 0.1% 3-phenyl-1-propyne as side products. The quantitative and likely barrierless formation of indene yields important insights into the role resonance stabilized radicals play in the formation of polycyclic hydrocarbons.

The Role of Chemists and Chemical Engineers in a Sustainable World.

Where we fit in to the puzzle: The world is standing at a crossroads and with large-scale challenges and difficulties facing us all, the role of chemists in upcoming developments will continue to be a crucial one. In this article, the United Nations 17 Sustainable Goals are outlined and highlighted to show where chemists will fit into the puzzle of trying to reshape and reform the environment and industrial practices so that targets can be reached.