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Potassium carbonate anhydrous, free-flowing, Redi-Dri™, ReagentPlus®, 99%; CAS Number: 584-08-7; EC Number: 209-529-3; Synonyms: Pottasche; Linear Formula: K2CO3; find Sigma-Aldrich-900501 MSDS, related peer-reviewed papers, technical documents, similar products & more at Sigma-Aldrich

Potassium carbonate anhydrous, free-flowing, Redi-Dri, ReagentPlus, 99 584-08-7

anhydrous, free-flowing, Redi-Dri&#8482;, ReagentPlus&#174;, 99%

Potassium carbonate anhydrous, free-flowing, Redi-Dri&#8482;, ReagentPlus&#174;, 99%

Potassium carbonate

Chelating N-heterocyclic carbene ligands in palladium-catalyzed Heck-type reactions.

The cobalt-catalyzed Diels-Alder reaction of trimethylsilyl-substituted alkynes with 1,3-dienes led to dihydroaromatic intermediates which were transformed into iodobenzene derivatives. For this transformation, the dihydroaromatic intermediates had to be oxidized and the trimethylsilyl-substituted arene had to undergo a silicon-iodine exchange reaction. For this purpose, a number of oxidizing agents and iodonium sources were tested in order to realize the desired two transformations in a single step. Eventually, the combination of tert-butyl hydroperoxide (TBHP), zinc iodide, and potassium carbonate led to the desired oxidation/iodination in good to excellent yields in a short reaction time at ambient temperatures.

Synthesis of polysubstituted iodobenzene derivatives from alkynylsilanes and 1,3-dienes via diels-alder/oxidation/iodination reaction sequence.

Heck reaction using palladium complexed to dendrimers on silica.

Polyamide interfacial composite membranes prepared from m-phenylene diamine, trimesoyl chloride and a new disulfonated diamine.

ortho-Arylation of ortho-substituted benzoic acids is a challenging process due to the tendency of the reaction products toward Pd-catalyzed protodecarboxylation. A simple method for preventing decarboxylation in sterically hindered benzoic acids is reported. The method described represents a reliable and broadly applicable entry to 2-aryl-6-substituted benzoic acids.

Direct ortho-arylation of ortho-substituted benzoic acids: overriding Pd-catalyzed protodecarboxylation.

This work explores the feasibility of orange peel, a citrus processing biomass as an alternative precursor for preparation of activated carbon (OPAC) via microwave assisted K(2)CO(3) activation. The operational parameters, chemical impregnation ratio, microwave power and irradiation time on the carbon yield and adsorption capability were investigated. The virgin characteristics of OPAC were examined by pore structural analysis, scanning electron microscopy, Fourier transform infrared spectroscopy, nitrogen adsorption isotherm, elemental analysis, surface acidity/basicity and zeta potential measurement. The optimum conditions resulted in OPAC with a monolayer adsorption capacity of 382.75 mg/g for methylene blue and carbon yield of 80.99%. The BET surface area, Langmuir surface area and total pore volume were identified to be 1104.45 m(2)/g, 1661.04 m(2)/g and 0.615 m(3)/g, respectively. Equilibrium data were simulated using the Langmuir, Freundlich, Dubinin-Radushkevich, Redlich-Peterson, and Toth isotherms, and kinetic data were fitted to the pseudo-first-order, pseudo-second-order and Elovich kinetic models.

Preparation, characterization and evaluation of adsorptive properties of orange peel based activated carbon via microwave induced K2CO3 activation.

Sunflower seed oil residue, a by-product of sunflower seed oil refining, was utilized as a feedstock for preparation of activated carbon (SSHAC) via microwave induced K(2)CO(3) chemical activation. SSHAC was characterized by Fourier transform infrared spectroscopy, nitrogen adsorption-desorption and elemental analysis. Surface acidity/basicity was examined with acid-base titration, while the adsorptive properties of SSHAC were quantified using methylene blue (MB) and acid blue 15 (AB). The monolayer adsorption capacities of MB and AB were 473.44 and 430.37 mg/g, while the Brunauer-Emmett-Teller surface area, Langmuir surface area and total pore volume were 1411.55 m(2)/g, 2137.72 m(2)/g and 0.836 cm(3)/g, respectively. The findings revealed the potential to prepare high surface area activated carbon from sunflower seed oil residue by microwave irradiation.

Preparation and characterization of activated carbon from sunflower seed oil residue via microwave assisted K2CO3 activation.

Heck reaction catalyzed by phospha-palladacycles in non-aqueous ionic liquids.

Rice husk (RH), an abundant by-product of rice milling, was used for the preparation of activated carbon (RHAC) via KOH and K(2)CO(3) chemical activation. The activation process was performed at the microwave input power of 600 W for 7 min. RHACs were characterized by low temperature nitrogen adsorption/desorption, scanning electron microscopy and Fourier transform infrared spectroscopy. The adsorption behavior was examined using methylene blue as adsorbate. The K(2)CO(3)-activated sample showed higher yield and better pore structures and adsorption capacity development than the KOH-activated sample, with a BET surface area, total pore volume and monolayer adsorption capacity of 1165 m(2)/g, 0.78 cm(3)/g and 441.52 mg/g, respectively. The results revealed the feasibility of microwave heating for preparation of high surface area activated carbons from rice husks via K(2)CO(3) activation.

Utilization of rice husks as a feedstock for preparation of activated carbon by microwave induced KOH and K2CO3 activation.

This study examined the effects of additives of potassium carbonate (K2CO3) and zinc oxide (ZnO) on the pyrolysis of waste sunflower-oil cake using a 60 kW pilot-scale plasma torch reactor. The major gaseous products were CO and H2. The productions of CO and CH4 increased while that of H2 decreased with the addition of K2CO3. The use of ZnO reduced while enhanced the formation of CO and H2, respectively. In order to match the appeal of resource reutilization, one can use the waste K2CO3 resulted from the sorption of CO2 with KOH in greenhouse gas control and the waste ZnO obtained from the melting process as additives for the co-pyrolysis of sunflower-oil cake, yielding fuels rich in CO and H2, respectively.

Co-pyrolysis of sunflower-oil cake with potassium carbonate and zinc oxide using plasma torch to produce bio-fuels.

Wood sawdust was converted into a high-quality activated carbon (WSAC) via microwave-induced K(2)CO(3) activation. The operational variables including chemical impregnation ratio, microwave power and irradiation time on the carbon yield and adsorption capability were identified. The surface physical characteristics of WSAC were examined by pore structural analysis, scanning electron microscopy and nitrogen adsorption isotherms. The adsorptive behavior of WSAC was quantified using methylene blue as model dye compound. The best conditions resulted in activated carbon with a monolayer adsorption capacity of 423.17 mg/g and carbon yield of 80.75%. The BET surface area, Langmuir surface area and total pore volume were corresponded to 1496.05 m(2)/g, 2245.53 m(2)/g and 0.864 cm(3)/g, respectively. The findings support the potential to prepare high surface area and mesoporous activated carbon from wood sawdust by microwave assisted chemical activation.

Mesoporous activated carbon from wood sawdust by K2CO3 activation using microwave heating.

We have measured the single-molecule conductance of a family of oligothiophenes comprising 1-6 thiophene moieties terminated with methyl-sulfide linkers using the scanning tunneling microscope-based break-junction technique. We find an anomalous behavior: the peak of the conductance histogram distribution does not follow a clear exponential decay with increasing number of thiophene units in the chain. The electronic properties of the materials were characterized by optical spectroscopy and electrochemistry to gain an understanding of the factors affecting the conductance of these molecules. We postulate that different conformers in the junction are a contributing factor to the anomalous trend in the observed conductance as a function of molecule length.

Length-dependent conductance of oligothiophenes.

Unconventional star-shaped liquid crystals (abbreviated as SiLCs) were successfully synthesized by chemically connecting four cyanobiphenyl anisotropic mesogens to the periphery of a super-hydrophobic and ultra-flexible cyclic tetramethyltetrasiloxane ring with flexible hexyl chains. Based on the combined experimental techniques of differential scanning calorimetry (DSC), cross-polarized optical microscopy (POM), solid-state carbon-13 ((13)C) nuclear magnetic resonance (NMR) spectroscopy and one-dimensional (1D) wide-angle X-ray diffraction (WAXD), it was found that the SiLC molecule exhibited the monotropic phase transition from a LC phase to a crystalline phase. The crystalline phase was only detected during slow heating processes above its glass transition temperature, while a LC phase was formed both during cooling and during heating processes. The hierarchical superstructures were identified from the structure-sensitive 2D WAXD of the macroscopically oriented SiLC film and confirmed by selected area electron diffraction (SAED) of the SiLC single crystals. The molecular packing symmetry in the monoclinic unit cell was further investigated by computer simulations on the real and reciprocal spaces. Macroscopically oriented SiLC hierarchical superstructures on the different length scales may provide the targeted physical properties, which can allow us to apply SiLC molecules in the fields of electro-optical devices and nonlinear optics.

Hierarchical superstructures from a star-shaped molecule consisting of a cyclic oligosiloxane with cyanobiphenyl moieties.

The facile loading of sensitive and fragile biomacromolecules, such as glucose oxidase, hemoglobin, and ribonucleic acid (RNA), via synthetic vehicles directly in pure aqueous media is an important technical challenge. Inspired by the nucleus pore complex that connects the cell nucleus and the cytoplasm across the nuclear envelope, here we describe the development of a kind of polymeric nuclear envelope-like vesicle (NEV) to address this problem. The NEV is tailored to form the polymer pore complex (70 nm, similar to a nucleus pore complex) within the vesicle membrane based on nanophase segregation, which is confirmed via fluorescence spectrometry and dynamic light scattering (DLS) during self-assembly. This pH-triggered polymer pore complex can mediate the transportation of biomacromolecules across the vesicle membrane. Moreover, the NEVs facilitate the natural consecutive enzyme-catalyzed reactions via the H(+) sponge effect. This simple strategy might also be extended for mimicking other synthetic cell organelles.

Preparation and mechanism insight of nuclear envelope-like polymer vesicles for facile loading of biomacromolecules and enhanced biocatalytic activity.

The purpose of the research was to investigate the effect of moisture content of cellulose on the degradation of a drug in binary mixtures with cellulose. Physical mixtures of acetylsalicylic acid and two forms of cellulose, either microcrystalline cellulose or low crystalline cellulose, in the proportion 1:1 were stored at 50°C at a series of relative humidities (0-90%) for up to 175 days. The degradation rate constant of the drug increased with increased cellulose moisture content in a bi-regional fashion, with a low and a high degradation rate region. The shift from region 1 to 2 occurred at higher moisture content for the low crystalline cellulose. The relationships between rate constant and the temperature of maximum endothermic value overlapped for the two celluloses. It is proposed that the amount of water available for degradation of a solid drug is controlled by the water presenting capacity of cellulose which is dependent of the mechanism of sorption of water in cellulose. The water sorption of water can for cellulose satisfactorily be described by a two-site residence model with cellulose crystallinity as the structural correlate to the distribution between the two residence sites.

The crystallinity of cellulose controls the physical distribution of sorbed water and the capacity to present water for chemical degradation of a solid drug.

Hepatitis B virus (HBV) is a causative reagent that frequently causes progressive liver diseases, leading to the development of acute, chronic hepatitis, cirrhosis, and eventually hepatocellular carcinoma (HCC). Despite several antiviral drugs including interferon-α and nucleotide derivatives are approved for clinical treatment for HBV, critical issues remain unresolved, e.g., low-to-moderate efficacy, adverse side effects, and resistant strains. In this study, novel Paeonol-phenylsulfonyl derivatives were synthesized and their antiviral effect against HBV was evaluated. The experimental results indicated that these compounds process significant antiviral potential, including the inhibition of viral antigen expression and secretion, and the suppression of HBV viral DNA replication. Among compounds synthesized in this research, compound 2-acetyl-5-methoxyphenyl 4-methoxybenzenesulfonate (7f) had the most potent inhibitory activity with IC50 value of 0.36 μM, and high selectivity index, SI (TC50/IC50) 47.75; which exhibited an apparent inhibition effect on viral gene expression and viral propagation in cell culture model. So, we believe our compounds could serve as reservoir for antiviral drug development.

Design, synthesis, and bioevaluation of paeonol derivatives as potential anti-HBV agents.

Triamcinolone acetonide (TA) is prohibited in sport competitions using systemic administrations (e.g., intramuscular, IM), and it is allowed by other routes (e.g., intranasal, IN, or topical, TOP). A reporting level of 30 ng/mL is used to discriminate between forbidden and allowed administrations. We examined urinary profiles of TA metabolites after TOP, IN and IM administrations to evaluate the suitability of the current reporting level and to define the best criteria to discriminate between these administrations. TA was administered to healthy volunteers by different routes: a single IM dose (n=2), IN doses for three days (n=6), and TOP doses for five days followed by a single IM dose (n=8). Urine samples were collected at different time intervals and they were analyzed by liquid chromatography-tandem mass spectrometry to measure TA and eight metabolites. After TOP and IN administrations, concentrations of the metabolites were significantly lower (p<0.05) than after IM administrations. Concentrations of TA after IM administration were lower than 30 ng/mL for all volunteers (range 0.7-29.7 ng/mL), and they were lower than 5 ng/mL after multiple IN or TOP doses (0.1-3.6 ng/mL and 0-1.7 ng/mL, respectively). For 6β-hydroxy-TA, the main TA metabolite, greater concentrations were obtained: 10.7-469.1 ng/mL, 2.2-90.6 ng/mL and 0-57.2 ng/mL after IM, IN and TOP administrations, respectively. These results suggest that the current reporting level is not suitable to detect forbidden IM administration of TA. A lower concentration of the parent drug or the use of specific metabolites could discriminate IM from TOP or IN administrations.

Evaluation of the reporting level to detect triamcinolone acetonide misuse in sports.

Anti-doping laboratories need to be aware of evolutions on the steroid market and elucidate steroid metabolism to identify markers of misuse. Owing to ethical considerations, in vivo and in vitro models are preferred to human excretion for nonpharmaceutical grade substances. In this study the chimeric mouse model and human liver microsomes (HLM) were used to elucidate the phase I metabolism of a new steroid product containing, according to the label, methylstenbolone. Analysis revealed the presence of both methylstenbolone and methasterone, a structurally closely related steroid. Via HPLC fraction collection, methylstenbolone was isolated and studied with both models. Using HLM, 10 mono-hydroxylated derivatives (U1-U10) and a still unidentified derivative of methylstenbolone (U13) were detected. In chimeric mouse urine only di-hydroxylated metabolites (U11-U12) were identified. Although closely related, neither methasterone nor its metabolites were detected after administration of isolated methylstenbolone. Administration of the steroid product resulted mainly in the detection of methasterone metabolites, which were similar to those already described in the literature. Methylstenbolone metabolites previously described were not detected. A GC-MS/MS multiple reaction monitoring method was developed to detect methylstenbolone misuse. In one out of three samples, previously tested positive for methasterone, methylstenbolone and U13 were additionally detected, indicating the applicability of the method.

Metabolism of methylstenbolone studied with human liver microsomes and the uPA⁺/⁺-SCID chimeric mouse model.

Microwave technology has been successfully applied to enhance the effectiveness of radiolabeling reactions. The use of a microwave as a source of heat energy can allow chemical reactions to proceed over much shorter reaction times and in higher yields than they would do under conventional thermal conditions. A microwave reactor developed by Resonance Instrument Inc. (Model 520/521) and CEM (PETWave) has been used exclusively for the synthesis of radiolabeled agents for positron emission tomography by numerous groups throughout the world. In this study, we have developed a novel resonant-type microwave reactor powered by a solid-state device and confirmed that this system can focus microwave power on a small amount of reaction solution. Furthermore, we have demonstrated the rapid and facile radiosynthesis of 16α-[(18)F]fluoroestradiol, 4-[(18)F]fluoro-N-[2-(1-methoxyphenyl)-1-piperazinyl]ethyl-N-2-pyridinylbenzamide, and N-succinimidyl 4-[(18)F]fluorobenzoate using our newly developed microwave reactor.

Development of a resonant-type microwave reactor and its application to the synthesis of positron emission tomography radiopharmaceuticals.

Bisphenol A (BPA) and triclosan (TCS) are ubiquitous environmental phenols exhibiting endocrine disrupting activities that may be involved in various health disorders in humans. There is a need to measure separately free forms and conjugated metabolites because only the former are biologically active. We have developed sensitive methods using isotope-dilution liquid chromatography-tandem mass spectrometry for individual measurements of free BPA and TCS as well as their metabolites, BPA glucuronide (BPAG), BPA monosulfate (BPAS), BPA disulfate (BPADS), TCS glucuronide (TCSG) and TCS sulfate (TCSS) in urine. Comparative analyses of urine samples from 46 volunteers living in the Quebec City area using the new methods and a GC-MS/MS method previously used in our laboratory revealed very strong correlations for total BPA (Spearman's rs=0.862, p<0.0001) and total TCS concentrations (rs=0.942, p<0.0001). Glucuronide metabolites were the most abundant BPA and TCS species in urine samples (>94% of total urinary concentrations). Unconjugated TCS concentrations represented a small proportion of total TCS species (median=1.6%) but its concentration was likely underestimated due to losses by adsorption to the surface of polypropylene tubes used for sample storage. To our knowledge, we are the first to report levels of free, sulfated and glucuronidated TCS levels in human urine.

Determination of bisphenol A, triclosan and their metabolites in human urine using isotope-dilution liquid chromatography-tandem mass spectrometry.

Redi-Dri™ prevents hygroscopic powders, such as inorganic salts, from absorbing moisture and forming clumps, leaving the salts free-flowing every time.

Potassium carbonate

anhydrous, free-flowing, Redi-Dri^™, ReagentPlus^®, 99%

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