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Phosphoric acid

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https://www.readbyqxmd.com/read/28730207/asymmetric-br%C3%A3-nsted-acid-catalysis-with-chiral-carboxylic-acids
#1
REVIEW
Chang Min, Daniel Seidel
Chiral Brønsted acids have found widespread applications as organocatalysts. Weakly acidic species such as diols and (thio)ureas, typically classified as hydrogen bonding catalysts, as well as stronger phosphoric acids, have proven to be highly effective in catalyzing a wide range of asymmetric transformations. In contrast, the use of chiral carboxylic acids as Brønsted acid catalysts is much less developed but has recently garnered increased attention. Given that their pKa's generally lie between those of typical hydrogen bond donors and chiral phosphoric acids, chiral carboxylic acids provide the opportunity to activate a different set of substrates requiring intermediate catalyst acidity...
July 21, 2017: Chemical Society Reviews
https://www.readbyqxmd.com/read/28727264/phosphorylated-polyacrylonitrile-fiber-as-an-efficient-and-greener-acetalization-catalyst
#2
Gang Xu, Jian Cao, Yali Zhao, Lishuo Zheng, Minli Tao, Wenqin Zhang
A novel solid acid catalyst (PANEAPF) was developed by immobilization of phosphoric acid on polyacrylonitrile fiber via covalent bond. Various characterization techniques such as elemental analysis (EA), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), etc. were utilized to confirm the successful grafting and the stability of the fiber catalysts during application. The PANEAPF showed high catalytic activity in the acetalization of aldehydes due to the high utilization efficiency of its functionalized acid sites...
July 20, 2017: Chemistry, An Asian Journal
https://www.readbyqxmd.com/read/28726380/assessment-of-the-stability-and-operability-of-cobalt-phosphide-electrocatalyst-for-hydrogen-evolution
#3
Hyun S Ahn, Allen J Bard
Transition metal phosphides have been investigated heavily as hydrogen evolution reaction (HER) catalysts. One of the most active transition metal phosphides, CoP, has been tested for its stability and operability under mild conditions that it may be exposed to in its applications (photoelectrochemistry and artificial photosynthesis). Surface-interrogation scanning electrochemical microscopy (SI-SECM) revealed that CoP HER catalyst is vulnerable to oxidation (by oxygen and chemical oxidants). The degradation mechanism was shown to be surface oxidation by dioxygen, followed by acid etching of the oxidized layer...
July 20, 2017: Analytical Chemistry
https://www.readbyqxmd.com/read/28721100/shear-bond-strength-of-different-surface-treatments-in-bulk-fill-microhybrid-and-nanoparticle-repair-resins
#4
Rudys Rodolfo de Jesus Tavarez, Lauber Jose Dos Santos Almeida Júnior, Tayanne Christine Gomes Guará, Izabella Santos Ribeiro, Etevaldo Matos Maia Filho, Leily Macedo Firoozmand
OBJECTIVES: The purpose of this study was to evaluate the influence of surface treatment and different types of composite resin on the microshear bond strength of repairs. MATERIALS AND METHODS: Seventy-two specimens (n=72) were prepared using a nanoparticle resin and stored in artificial saliva at 37 ± 1°C for 24 h. After this period, the specimens (n=24) were restored with microhybrid resin P60 (3M ESPE), nanoparticle resin Filtek Z350 (3M ESPE), and Bulk Fill Surefil SDR Flow (Dentsply) composite resins...
2017: Clinical, Cosmetic and Investigational Dentistry
https://www.readbyqxmd.com/read/28718012/implant-decontamination-with-phosphoric-acid-during-surgical-peri-implantitis-treatment-a-rct
#5
Diederik F M Hentenaar, Yvonne C M De Waal, Hans Strooker, Henny J A Meijer, Arie-Jan Van Winkelhoff, Gerry M Raghoebar
BACKGROUND: Peri-implantitis is known as an infectious disease that affects the peri-implant soft and hard tissue. Today, scientific literature provides very little evidence for an effective intervention protocol for treatment of peri-implantitis. The aim of the present randomized controlled trial is to evaluate the microbiological and clinical effectiveness of phosphoric acid as a decontaminating agent of the implant surface during surgical peri-implantitis treatment. METHODS: Peri-implantitis lesions were treated with resective surgical treatment aimed at peri-implant granulation tissue removal, bone recontouring, and pocket elimination...
December 2017: International Journal of Implant Dentistry
https://www.readbyqxmd.com/read/28713501/removal-of-acid-orange-7-dye-from-aqueous-solutions-by-adsorption-onto-kenya-tea-pulps-granulated-shape
#6
Behnaz Naraghi, Fahimeh Zabihi, Mohammad Reza Narooie, Mahdi Saeidi, Hamed Biglari
BACKGROUND AND AIM: Water resources pollution control is one of the main challenges of our time for researchers. Colored wastewater discharges caused by textile industry activities has added to the concern. In this study, removal of Acid Orange 7 dye (AO7) using Kenya Tea residue absorbent (granular) has been studied. METHODS: This cross-sectional study was conducted in 2016. In this work, initially, tea residue was prepared in three forms of raw, treated with concentrated phosphoric acid, and carbonated, at temperatures of 350, 450 and 500 °C in the chemistry laboratory of Gonabad University of Medical Sciences...
May 2017: Electronic Physician
https://www.readbyqxmd.com/read/28712552/insights-into-head-column-field-amplified-sample-stacking-part-ii-study-of-the-behavior-of-the-electrophoretic-system-after-electrokinetic-injection-of-cationic-compounds-across-a-short-water-plug
#7
Jozef Šesták, Wolfgang Thormann
Part I on head-column field-amplified sample stacking comprised a detailed study of the electrokinetic injection of a weak base across a short water plug into a phosphate buffer at low pH. The water plug is converted into a low conductive acidic zone and cationic analytes become stacked at the interface between this and a newly formed phosphoric acid zone. The fundamentals of electrokinetic processes occurring thereafter were studied experimentally and with computer simulation and are presented as part II. The configuration analyzed represents a discontinuous buffer system...
June 30, 2017: Journal of Chromatography. A
https://www.readbyqxmd.com/read/28708906/effectiveness-of-periapical-radiography-versus-cone-beam-computed-tomography-with-different-kilovoltage-settings-in-the-detection-of-chemically-created-peri-implant-bone-defects-an-in-vitro-study
#8
Lucas Rodrigues Pinheiro, William C Scarfe, Marcelo Augusto de Oliveira Sales, Bruno Felipe Gaia, Arthur Rodriguez Gonzalez Cortes, Marcelo Gusmão Paraiso Cavalcanti
PURPOSE: To determine the effectiveness of cone beam computed tomography (CBCT) images obtained with different kilovoltage settings compared with intraoral periapical photostimulable storage phosphor (PSP) plate images in the detection of chemically created peri-implant defects utilizing a bovine rib bone model in vitro. MATERIALS AND METHODS: After placing 80 implants in bovine ribs, peri-implant circumferential bone defects of different sizes were created with 70% perchloric acid...
July 2017: International Journal of Oral & Maxillofacial Implants
https://www.readbyqxmd.com/read/28708408/comprehension-of-the-effect-of-a-hydroxyl-group-in-ancillary-ligand-on-phosphorescent-property-for-heteroleptic-ir-iii-complexes-a-computational-study-using-quantitative-prediction
#9
Xiaolin Wang, Huiqing Yang, Yaping Wen, Li Wang, Junfeng Li, Jinglai Zhang
A new Ir(III) complex (dfpypya)2Ir(pic-OH) (2) is theoretically designed by introduction of a simple hydroxyl group into the ancillary ligand on the basis of (dfpypya)2Ir(pic) (1) with the aim to get the high-efficiency and stable blue-emitting phosphors, where dfpypya is 3-methyl-6-(2',4'-difluoro-pyridinato)pyridazine, pic is picolinate, and pic-OH is 3-hydroxypicolinic acid. The other configuration (dfpypya)2Ir(pic-OH)' (3) is also investigated to compare with 2. The difference between 2 and 3 is whether the intramolecular hydrogen bond is formed in the (dfpypya)2Ir(pic-OH)...
July 14, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28708391/enantioselective-synthesis-of-anti-1-2-oxaborinan-3-enes-from-aldehydes-and-1-1-di-boryl-alk-3-enes-using-ruthenium-and-chiral-phosphoric-acid-catalysts
#10
Tomoya Miura, Junki Nakahashi, Wang Zhou, Yota Shiratori, Scott G Stewart, Masahiro Murakami
A cationic ruthenium(II) complex catalyzes double-bond transposition of 1,1-di(boryl)alk-3-enes to generate in situ 1,1-di(boryl)alk-2-enes, which then undergo chiral phosphoric acid-catalyzed allylation of aldehydes producing homoallylic alcohols with a (Z)-vinylboronate moiety. 1,2-Anti stereochemistry is installed in an enantioselective manner. The (Z)-geometry forged in the products allows their isolation in a form of 1,2-oxaborinan-3-enes, upon which further synthetic transformations are operated.
July 14, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28701415/structure-of-psd-95-map1a-complex-reveals-unique-target-recognition-mode-of-maguk-gk-domain
#11
Yitan Xia, Yuan Shang, Rongguang Zhang, Jinwei Zhu
The PSD-95 family of membrane-associated guanylate kinases (MAGUKs) are major synaptic scaffold proteins and play crucial roles in the dynamic regulation of dendritic remodeling which is understood to be the foundation of synaptogenesis and synaptic plasticity. The guanylate kinase (GK) domain of MAGUK family proteins functions as a phosphor-peptide binding module. However, the GK domain of PSD-95 has been found to directly bind to a peptide sequence within the C-terminal region of neuronal-specific microtubule-associated protein 1A (MAP1A), though the detailed molecular mechanism governing this phosphorylation-independent interaction at the atomic level is missing...
July 12, 2017: Biochemical Journal
https://www.readbyqxmd.com/read/28691026/quercetin-attenuates-vascular-calcification-through-suppressed-oxidative-stress-in-adenine-induced-chronic-renal-failure-rats
#12
Xue-Ying Chang, Lei Cui, Xing-Zhi Wang, Lei Zhang, Dan Zhu, Xiao-Rong Zhou, Li-Rong Hao
BACKGROUND: This study investigated whether quercetin could alleviate vascular calcification in experimental chronic renal failure rats induced by adenine. METHODS: 32 adult male Wistar rats were randomly divided into 4 groups fed normal diet, normal diet with quercetin supplementation (25 mg/kg·BW/d), 0.75% adenine diet, or adenine diet with quercetin supplementation. All rats were sacrificed after 6 weeks of intervention. Serum renal functions biomarkers and oxidative stress biomarkers were measured and status of vascular calcification in aorta was assessed...
2017: BioMed Research International
https://www.readbyqxmd.com/read/28690167/evaluation-of-lignins-from-side-streams-generated-in-an-olive-tree-pruning-based-biorefinery-bioethanol-production-and-alkaline-pulping
#13
José I Santos, Úrsula Fillat, Raquel Martín-Sampedro, María E Eugenio, María J Negro, Ignacio Ballesteros, Alejandro Rodríguez, David Ibarra
In modern lignocellulosic-based biorefineries, carbohydrates can be transformed into biofuels and pulp and paper, whereas lignin is burned to obtain energy. However, a part of lignin could be converted into value-added products including bio-based aromatic chemicals, as well as building blocks for materials. Then, a good knowledge of lignin is necessary to define its valorisation procedure. This study characterized different lignins from side-streams produced from olive tree pruning bioethanol production (lignins collected from steam explosion pretreatment with water or phosphoric acid as catalysts, followed by simultaneous saccharification and fermentation process) and alkaline pulping (lignins recovered from kraft and soda-AQ black liquors)...
July 6, 2017: International Journal of Biological Macromolecules
https://www.readbyqxmd.com/read/28689290/ricinus-communis-l-castor-bean-as-a-potential-candidate-for-revegetating-industrial-waste-contaminated-sites-in-peri-urban-greater-hyderabad-remarks-on-seed-oil
#14
Ravi Kiran Boda, Narasimha Vara Prasad Majeti, Sateesh Suthari
Ricinus communis L. (castor bean or castor oil plant) was found growing on metal-contaminated sites (4) of peri-urban Greater Hyderabad comprises of erstwhile industrial areas viz Bollaram, Patancheru, Bharatnagar, and Kattedan industrial areas. During 2013-2017, about 60 research papers have appeared focusing the role of castor bean in phytoremediation of co-contaminated soils, co-generation of biomaterials, and environmental cleanup, as bioenergy crop and sustainable development. The present study is focused on its use as a multipurpose phytoremediation crop for phytostabilization and revegetation of waste disposed peri-urban contaminated soils...
July 9, 2017: Environmental Science and Pollution Research International
https://www.readbyqxmd.com/read/28688005/ab-initio-study-of-hydrogen-bonding-in-the-h3po2-dimer-and-h3po2-dmf-complex
#15
Irina V Fedorova, Lyubov P Safonova
The molecular structures and H-bonding interactions in the phosphinic acid dimer and the complex of phosphinic acid with N,N-dimethylformamide (DMF) were investigated by density functional theory calculations at the B3LYP level of theory. In order to better understand these phenomena, the individual molecules were also studied. The results were compared with previously obtained data for similar H-bonded complexes of phosphoric and phosphorous acids with DMF. Various correlations were found between geometric characteristics and parameters derived from Bader's theory and natural bond orbital analysis...
August 2017: Journal of Molecular Modeling
https://www.readbyqxmd.com/read/28686413/atomically-thin-layers-of-graphene-and-hexagonal-boron-nitride-made-by-solvent-exfoliation-of-their-phosphoric-acid-intercalation-compounds
#16
Nina I Kovtyukhova, Nestor Perea-Lopez, Mauricio Terrones, Thomas E Mallouk
The development of scalable and reliable techniques for the production of the atomically thin layers of graphene and hexagonal boron nitride (h-BN) in bulk quantities could make these materials a powerful platform for devices and composites that impact a wide variety of technologies. To date a number of practical exfoliation methods have been reported that are based on sonicating or stirring powdered graphite or h-BN in common solvents. However, the products of these experiments consist mainly of few-layer sheets and contain only a small fraction of monolayers...
July 7, 2017: ACS Nano
https://www.readbyqxmd.com/read/28682287/effect-of-surface-treatments-on-the-bond-strength-of-self-etching-adhesive-agents-to-dentin
#17
M Jacinta Mc Santos, Max Doria Costa, Heleine Maria Chagas Rêgo, José H Rubo, Gildo C Santos
The aim of this study was to investigate the influence of different surface treatments on the shear bond strength (SBS) of self-etching adhesive systems to dentin. Ninety freshly extracted noncarious human molars were sectioned mesiodistally and embedded in chemically cured resin with the buccal or lingual surfaces facing upward. Superficial dentin was exposed, and specimens were randomly assigned to 3 groups, according to the self-etching adhesive system utilized: Clearfil SE Bond (2-step), Scotchbond Universal (1-step), and Clearfil S³ Bond Plus (1-step)...
July 2017: General Dentistry
https://www.readbyqxmd.com/read/28681891/enantioselective-synthesis-of-cyclic-quaternary-%C3%AE-amino-acid-derivatives-by-chiral-phosphoric-acid-catalysis
#18
Lei Wang, Abdul Rahman, Xufeng Lin
A highly enantioselective aza-Friedel-Crafts reaction of N-sulfonyl cyclic ketimines with indoles catalyzed by chiral phosphoric acids has been developed. This methodology provides an efficient and facile route to indole-containing chiral cyclic α-amino acid derivatives bearing a quaternary stereocenter in high yields and up to 98% enantioselectivity.
July 19, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28678195/quality-control-of-the-root-and-rhizome-of-helminthostachys-zeylanica-daodi-ugon-by-hplc-using-quercetin-and-ugonins-as-markers
#19
Kun-Chang Wu, Chun-Pin Kao, Yu-Ling Ho, Yuan-Shiun Chang
Daodi-Ugon is the dried root and rhizome of Helminthostachys zeylanica (L.) Hook. and has been used for centuries in the treatment of inflammation, fever, pneumonia, burns, and various disorders. However, the chromatographic methods to determine the phytochemical composition of H. zeylanica have never been reported. This study not only aims to develop a valid high-performance liquid chromatography (HPLC) method and to establish a chromatographic fingerprint for the quality control of H. zeylanica, it also establish the proposed content limits of Quercetin, Ugonin J, and Ugonin M...
July 5, 2017: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
https://www.readbyqxmd.com/read/28665539/minimalistic-liquid-assisted-route-to-highly-crystalline-%C3%AE-zirconium-phosphate
#20
Yu Cheng, Xiaodong Tony Wang, Stephan Jaenicke, Gaik-Khuan Chuah
Zirconium phosphates have potential applications in areas of ion-exchange, catalysis, photochemistry, and biotechnology. However, synthesis methodologies to form crystalline α-zirconium phosphate (Zr(HPO₄)₂·H₂O) typically involve the use of excess phosphoric acid, addition of HF or oxalic acid and long reflux times or hydrothermal conditions. Herein we report on a minimalistic sustainable route using only zirconium oxychloride and concentrated phosphoric acid to form highly crystalline α-zirconium phosphate within hours...
June 30, 2017: ChemSusChem
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