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https://www.readbyqxmd.com/read/29437289/ion-pair-sn2-reaction-of-oh-and-ch3cl-activation-strain-analyses-of-counterion-and-solvent-effects
#1
Jalal Z A Laloo, Lydia Rhyman, Olatz Larrañaga, Ponnadurai Ramasami, Matthias Bickelhaupt, Abel de Cozar Ruano
We have theoretically studied the non-identity SN2 reactions of MnOH(n-1) + CH3Cl (M+ = Li+, Na+, K+, and MgCl+; n = 0, 1) in the gas phase and in THF solution at OLYP/6-31++G(d,p) using PCM implicit solvation. We want to explore and understand the effect of the metal counterion M+ and solvation on the reaction profile and the stereoselectivity of these processes. To this end we have explored the potential energy surfaces of the backside (SN2-b) and frontside (SN2-f) pathways. To explain the computed trends, we have carried out analyses with an extended activation strain model (ASM) of chemical reactivity that includes the treatment of solvation effects...
February 13, 2018: Chemistry, An Asian Journal
https://www.readbyqxmd.com/read/29437280/nucleophilic-activation-of-sulfur-hexafluoride-metal-free-selective-degradation-by-phosphines
#2
Fabian Dielmann, Florenz Buß, Christian Mück-Lichtenfeld, Paul Mehlmann
The development of new methods for the chemical activation of the extremely inert greenhouse gas sulfur hexafluoride (SF6) not only is of current environmental interest, but also offers new opportunities for applications of SF6 as a reagent in organic synthesis. We herein report the first nucleophilic activation of SF6 by Lewis bases, namely by phosphines, which results either in its complete degradation to phosphine sulfides and difluorophosphoranes or in the selective conversion of SF6 into a bench-stable, crystalline salt containing the SF5- anion...
February 13, 2018: Angewandte Chemie
https://www.readbyqxmd.com/read/29430830/design-and-synthesis-of-spherical-multicomponent-aggregates-composed-of-core-shell-yolk-shell-and-hollow-nanospheres-and-their-lithium-ion-storage-performances
#3
Gi Dae Park, Yun Chan Kang
Micrometer-sized spherical aggregates of Sn and Co components containing core-shell, yolk-shell, hollow nanospheres are synthesized by applying nanoscale Kirkendall diffusion in the large-scale spray drying process. The Sn2 Co3 -Co3 SnC0.7 -C composite microspheres uniformly dispersed with Sn2 Co3 -Co3 SnC0.7 mixed nanocrystals are formed by the first-step reduction of spray-dried precursor powders at 900 °C. The second-step oxidation process transforms the Sn2 Co3 -Co3 SnC0.7 -C composite into the porous microsphere composed of Sn-Sn2 Co3 @CoSnO3 -Co3 O4 core-shell, Sn-Sn2 Co3 @CoSnO3 -Co3 O4 yolk-shell, and CoSnO3 -Co3 O4 hollow nanospheres at 300, 400, and 500 °C, respectively...
February 12, 2018: Small
https://www.readbyqxmd.com/read/29425811/an-in-vitro-study-on-the-influence-of-viscosity-and-frequency-of-application-of-fluoride-tin-solutions-on-the-progression-of-erosion-of-bovine-enamel
#4
Letícia Oba Sakae, Sávio José Cardoso Bezerra, Samira Helena João-Souza, Alessandra Buhler Borges, Idalina V Aoki, Ana Cecília Côrrea Aranha, Taís Scaramucci
OBJECTIVE: To evaluate the influence of the viscosity and frequency of application of solutions containing fluoride (F) and stannous chloride (SnCl2) on enamel erosion prevention. DESIGN: Bovine enamel specimens were randomly distributed into 12 groups (n = 10), according to the following study factors: solution (C: deionized water; F: 500 ppm F-; F + Sn: 500 ppm F- + 800 ppm Sn2+); viscosity (low and high); and frequency of application (once and twice a day)...
February 3, 2018: Archives of Oral Biology
https://www.readbyqxmd.com/read/29411914/enantiospecific-three-component-alkylation-of-furan-and-indole
#5
Mattia Silvi, Raffael Schrof, Adam Noble, Varinder Kumar Aggarwal
Furan and indole-derived boronate complexes react with alkyl iodides under radical (photoredox) or polar (SN2) conditions to generate three-component alkylation products with high efficiency and complete stereospecificity. The methodology allows the incorporation of versatile functional groups such as nitriles, ketones, esters, sulfones, and amides, providing rapid access to complex chiral heteroaromatic molecules in enantioenriched form. Interestingly, while indolyl boronate complexes react directly with alkyl halides through a polar pathway, furyl boronates require photoredox catalysis...
February 7, 2018: Chemistry: a European Journal
https://www.readbyqxmd.com/read/29378138/phe-71-in-type-iii-trypanosomal-protein-arginine-methyltransferase-7-tbprmt7-restricts-the-enzyme-to-monomethylation
#6
Tamar Caceres, Abishek Thakur, Owen M Price, Nicole Ippolito, Jun Li, Jun Qu, Orlando Acevedo, Joan Michelle Hevel
Protein arginine methyltransferase 7 (PRMT7) is unique within the PRMT family as it is the only isoform known to exclusively make monomethylarginine (MMA). Given its role in epigenetics, the mechanistic basis for the strict monomethylation activity is under investigation. It is thought that PRMT7 enzymes are unable to add a second methyl group because of steric hindrances in the active site which restrict them to monomethylation. To test this, we probed the active site of Trypanosomal PRMT7 (TbPRMT7) using accelerated molecular dynamics, site-directed mutagenesis, kinetic, binding, and product analyses...
January 29, 2018: Biochemistry
https://www.readbyqxmd.com/read/29372898/the-folate-binding-module-of-thermus-thermophilus-cobalamin-dependent-methionine-synthase-displays-a-distinct-variation-of-the-classical-tim-barrel-a-tim-barrel-with-a-twist
#7
Kazuhiro Yamada, Markos Koutmos
Methyl transfer between methyltetrahydrofolate and corrinoid molecules is a key reaction in biology that is catalyzed by a number of enzymes in many prokaryotic and eukaryotic organisms. One classic example of such an enzyme is cobalamin-dependent methionine synthase (MS). MS is a large modular protein that utilizes an SN2-type mechanism to catalyze the chemically challenging methyl transfer from the tertiary amine (N5) of methyltetrahydrofolate to homocysteine in order to form methionine. Despite over half a century of study, many questions remain about how folate-dependent methyltransferases, and MS in particular, function...
January 1, 2018: Acta Crystallographica. Section D, Structural Biology
https://www.readbyqxmd.com/read/29360360/benchmark-ab-initio-characterization-of-the-complex-potential-energy-surfaces-of-the-x-nh2y-x-y-f-cl-br-i-reactions
#8
Balint Hajdu, Gabor Czako
We report a comprehensive high-level explicitly correlated ab initio study on the X- + NH2Y [X,Y = F, Cl, Br, I] reactions characterizing the stationary points of the SN2 (Y- + NH2X) and proton-transfer (HX + NHY-) pathways as well as the reaction enthalpies of various endothermic additional product channels such as H- + NHXY, XY- + NH2, XY + NH2-, and XHY- + NH. Benchmark structures and harmonic vibrational frequencies are obtained at the CCSD(T)-F12b/aug-cc-pVTZ(-PP) level of theory, followed by CCSD(T)-F12b/aug-cc-pVnZ(-PP) [n = Q and 5] and core correlation energy computations...
January 23, 2018: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/29355427/stannous-fluoride-effects-on-gene-expression-of-streptococcus-mutans-and-actinomyces-viscosus
#9
Y Shi, R Li, D J White, A R Biesbrock
A genome-wide transcriptional analysis was performed to elucidate the bacterial cellular response of Streptococcus mutans and Actinomyces viscosus to NaF and SnF2. The minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of SnF2 were predetermined before microarray study. Gene expression profiling microarray experiments were carried out in the absence (control) and presence (experimental) of 10 ppm and 100 ppm Sn2+ (in the form of SnF2) and fluoride controls for 10-min exposures (4 biological replicates/treatment)...
February 2018: Advances in Dental Research
https://www.readbyqxmd.com/read/29342362/stereospecific-syntheses-of-enaminonitriles-and-%C3%AE-enaminoesters-via-domino-ring-opening-cyclization-droc-of-activated-cyclopropanes-with-pronucleophilic-malononitriles
#10
Amrita Saha, Aditya Bhattacharyya, Ranadeep Talukdar, Manas K Ghorai
Two novel synthetic protocols for the syntheses of highly functionalized five-membered carbocyclic enaminonitriles and β-enaminoesters have been developed via domino ring-opening cyclization (DROC) and DROC/decarboxylative tautomerization of activated cyclopropanes with malononitrile pronucleophiles, respectively. Both of the efficient strategies (yield up to 93%) have been generalized with various donor-acceptor and acceptor cyclopropanes as well as with malononitrile derivatives. The stereospecific variants of the two SN2-type DROC strategies have also been developed by employing enantiopure donor-acceptor (DA) cyclopropanes to synthesize the corresponding nonracemic products with excellent stereoselectivities (dr up to >99:1, ee up to >99%)...
January 17, 2018: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/29339227/a-novel-biphenolic-ligand-for-selective-mg2-and-zn2-ions-sensing-followed-by-colorimetric-spectroscopic-and-cell-imaging-methods
#11
Palanisamy Uma Maheswari, Duraisamy Renuga, H L Jeeva Kumari, Kandasamy Ruckmani
The (E)-2-((2-hydrohy-5-methylphenylimino) methyl) phenol ligand was synthesized. The receptor was characterized by IR, 1H and 13C NMR and CHN analysis. The ligand exhibits colorimetric and fluorometric sensing of Zn2+ and Mg2+ ions in semi-aqueous medium (DMSO-H2O). The receptor was tested with series of transition metal ions (Cr2+, Fe2+, Ni2+, Co2+, Cu2+, Zn2+) and heavy metal ions (Sn2+, Pd2+, Ce2+, Hg2+, Cd2+) and the essential human body elements like Ca2+, Mg2+, Na+ and K+ ions. The naked eye colorimetric sensing was absorbed only for Zn2+ and Mg2+...
January 12, 2018: European Journal of Pharmaceutical Sciences
https://www.readbyqxmd.com/read/29338222/computational-modelling-of-a-caged-methyl-cation-structure-energetics-and-vibrational-analysis
#12
Philippe B Wilson, Ian H Williams
DFT calculations for CH3+ within a constrained cage of water molecules permit the controlled manipulation of distances rax and req to "axial" and "equatorial" waters. Equatorial CH…O interactions catalyze methyl transfer (MT) between axial waters. Variation in rax has a greater effect on CH bond lengths and stretching force constants in the symmetric SN2-like transition structures than variation in req. In-plane bending frequencies are insensitive to these variations in cage dimensions, but axial interactions loosen the out-of-plane bending mode (OP) whereas equatorial interactions stiffen it...
January 16, 2018: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/29336720/a-novel-4-phenyl-amino-thiourea-derivative-designed-for-real-time-ratiometric-colorimetric-detection-of-toxic-pb2
#13
Yi S Guang, Xia Ren, Shuang Zhao, Quan Z Yan, Gang Zhao, Yao H Xu
The objective of this study was to develop a ratiometric and colorimetric organic sensor for Pb2+ detection in environmental samples. A new probe 4-phenyl amino thiourea (PAT) was designed and synthesized using hydrazine hydrate and phenyl isothiocyanate as raw materials. After its structure was characterized and confirmed, its UV-vis spectral property was investigated in detail. PAT possesses a specifically real-time, ratiometric and colorimetric response to Pb2+ in dimethyl formamide (DMF)/H2O (v/v = 9:1, pH = 7...
January 16, 2018: Journal of Environmental Science and Health. Part A, Toxic/hazardous Substances & Environmental Engineering
https://www.readbyqxmd.com/read/29336269/design-synthesis-and-biological-evaluation-of-new-azole-derivatives-as-potent-aromatase-inhibitors-with-potential-effects-against-breast-cancer
#14
Farzin Hadizadeh, Fatemeh Kalalinia, Mohammad Jouya, Alireza Khorsand Komachal, Aboutourabzadeh Seyed Mohammad, Gholamreza Karimi, Javad Behravan, Khalil Abnous, Leila Etemad, Hossein Kamali
PURPOSE: Some aromatase inhibitors are FDA-approved agents as first-line therapy in the treatment of endocrine-responsive breast cancer. In this study, we aimed to develop new azole derivatives with higher specificity and potency. METHODS: New aromatase inhibitors were designed by Molecular Operating Environment (MOE) software and synthesized in a one-step SN2 reaction. These compounds were characterized by melting point, 1H- and 13C-NMR, elemental analysis and mass spectra...
January 15, 2018: Anti-cancer Agents in Medicinal Chemistry
https://www.readbyqxmd.com/read/29335217/synthesis-and-characterisation-of-calix-4-arene-based-bis-triazole-bis-hexahydroquinoline-probing-highly-selective-fluorescence-quenching-towards-mercury-hg2-analyte
#15
Burhan Khan, Abdul Hameed, Aaliya Minhaz, Muhammad Raza Shah
In the present study, we are reporting the synthesis of a triazoles incorporated fluorescent hexahydroquinoline appended calix[4]arene 7 and its highly selective optical recognition ability towards Hg2+. The optical sensor 7 was synthesized via two different synthetic pathways and unambiguously characterized by mass spectrometry and NMR spectroscopy. The stoichiometric ratio between 7 and Hg2+ was determined as 1:1 based on Job's plot and ESI-MS analysis. The chemosensor 7 selectively recognized Hg2+ in the presence of competitive cations such as Cu2+, Cu1+, Co3+, Ni2+, Ag1+, Fe2+, Fe3+, Cr3+, Pb2+, Cd2+, Zn2+, Sn2+, Ti4+, Sb3+, In3+, Ba2+, Ca2+, and K1+...
January 10, 2018: Journal of Hazardous Materials
https://www.readbyqxmd.com/read/29313204/gas-phase-reactions-of-dimethyl-disulfide-with-aliphatic-carbanions-a-mass-spectrometry-and-computational-study
#16
Barbara Franczuk, Witold Danikiewicz
Ion-molecule reactions of Me2S2 with a wide range of aliphatic carbanions differing by structure and proton affinity values have been studied in the gas phase using mass spectrometry techniques and DFT calculations. The analysis of the spectra shows a variety of product ions formed via different reaction mechanisms, depending on the structure and proton affinity of the carbanion. Product ions of thiophilic reaction (m/z 47), SN2 (m/z 79), and E2 elimination - addition sequence of reactions (m/z 93) can be observed...
January 8, 2018: Journal of the American Society for Mass Spectrometry
https://www.readbyqxmd.com/read/29310904/synthesis-and-characterization-of-vangabhasma
#17
Babita Kale, Nilima Rajurkar
BACKGROUND: Bhasmas are unique Ayurvedic organometallic preparations used for medicinal purpose. Quality of bhasma depends upon quality of starting materials, processing ingredients, meticulous trituration and heating cycle. In Ayurveda, Vanga bhasma is traditional Indian medicine which is an organometallic preparation treated with plant extract. It is especially used in the treatments of diseases related to gastrointestinal tract and genitor urinary system. However detailed characterization studies after synthesis are important which shows authenticity of product...
January 5, 2018: Journal of Ayurveda and Integrative Medicine
https://www.readbyqxmd.com/read/29306291/dynamic-exit-channel-pathways-of-the-microsolvated-hoo-h2o-ch3cl-sn2-reaction-reaction-mechanisms-at-the-atomic-level-from-direct-chemical-dynamics-simulations
#18
Feng Yu
Microsolvated bimolecular nucleophilic substitution (SN2) reaction of monohydrated hydrogen peroxide anion [HOO-(H2O)] with methyl chloride (CH3Cl) has been investigated with direct chemical dynamics simulations at the M06-2X/6-31+G(d,p) level of theory. Dynamic exit-channel pathways and corresponding reaction mechanisms at the atomic level are revealed in detail. Accordingly, a product distribution of 0.85:0.15 is obtained for Cl-:Cl-(H2O), which is consistent with a previous experiment [D. L. Thomsen et al...
January 7, 2018: Journal of Chemical Physics
https://www.readbyqxmd.com/read/29306157/assessment-of-anaerobic-biodegradation-of-bis-2-chloroethyl-ether-in-groundwater-using-carbon-and-chlorine-compound-specific-isotope-analysis
#19
Daniel C Segal, Tomasz Kuder, Ravi Kolhatkar
Carbon and chlorine compound specific isotope analysis (CSIA) of bis(2-chloroethyl) ether (BCEE) was performed to distinguish the primary processes contributing to observed concentration reductions in an anaerobic groundwater plume. Laboratory microcosms were constructed to demonstrate and obtain isotopic enrichment factors and dual-element CSIA trends from two potential transformation processes (1) anaerobic biodegradation using saturated sediment samples from the field site (εC=-14.8 and εCl=-5.0) and (2) abiotic reactions with sulfide nucleophiles in water (εC=-12...
January 3, 2018: Science of the Total Environment
https://www.readbyqxmd.com/read/29300465/mixed-sulfur-and-iodide-based-lead-free-perovskite-solar-cells
#20
Riming Nie, Aarti Mehta, Byung-Wook Park, Hyoung-Woo Kwon, Jino Im, Sang Il Seok
Fully halide perovskite structures can only host inorganic metal cations such as Pb2+, Sn2+, and Ge2+ in the 2+ valence state to satisfy charge neutrality. This requirement limits the use of high-er-valence cations in preparing new types of perovskite materials for solar cells. Mixed chalcogenides and halides as anions in a perovskite structure, can enable the introduction of 3+ and 4+ charged cations in the place of the 2+ metal cations. Herein we report for the first time on the fabrication of solar cells exploiting methylammonium antimony sulfur diiodide (MASbSI2) perov-skite structures, as light harvesters...
January 4, 2018: Journal of the American Chemical Society
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