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21.
The reaction of benzaldehyde with aliphatic glycols was performed over Al-MCM-41 with various Si/Al ratios. The effects of various parameters like temperature, mole ratio, reaction time and catalyst amount on the formation of acetals were optimized. The mesoporous Al-MCM-41 (Si/Al ratio 36, 57, 81 and 108) were synthesized by hydrothermal method. The synthesized catalysts were characterized by X-ray diffraction (XRD), nitrogen adsorption–desorption isotherm (BET), thermo gravimetric-differential thermal analysis (TGA-DTA) and TEM techniques. The acidity of the catalysts was measured by pyridine adsorption followed by FT-IR analysis. TEM analysis showed that the honeycomb-like regular arrangement of hexagonal pores on the molecular sieves. The highly hydrophobic Al-MCM-41 (108) showed higher activity than the other Si/Al ratios. The activity of the catalysts showed the following order Al-MCM-41 (108) > Al-MCM-41 (81) > Al-MCM-41 (57) > Al-MCM-41 (36). The hydrophobicity and nucleophilicity of the glycols highly influences the conversion of benzaldehyde, it followed the order; hexylene glycol (HG) > propylene glycol (PG) > ethylene glycol (EG). The results showed that mole ratio of 1:3 (aldehyde:glycol) gave higher yield than the other mole ratios. 相似文献
22.
Mei‐Hsin Chiu Han Wu Jyh‐Cheng Chen Govindan Muthuraman Jyh‐Myng Zen 《Electroanalysis》2007,19(22):2301-2306
This work describes the development and application of an electrochemical cell specifically designed for disposable screen printed carbon electrodes (SPCE) suitable for simultaneous electrochemiluminescence (ECL) and amperometric detection in sequential injection analysis. The flow system with facility for photomultiplier tube via a fiber optic facing the SPCE is user‐friendly and makes the detection process very easy to operate. Instead of the need to constant deliver the chemiluminescence (CL) reagents to the reaction zone, sequential injection analysis allows a considerable reduction in the consumption of the sample and expensive CL reagents (such as Ru(bpy) salts). The utility of the analyzer was demonstrated for the detection of oxalate based on the ECL reaction with Ru(bpy) . Under optimized conditions, in the presence of 100 μM Ru(bpy) , the linear ranges of peak current and ECL light intensity for oxalate distinctly varied from 10 μM to 5 mM and 0.1 μM to 100 μM, respectively. In other words, the linear detection can be covered over a four‐order range with the combination of these two signals. 相似文献
23.
Unexpected Self‐Sorting Self‐Assembly Formation of a [4:4] Sulfate:Ligand Cage from a Preorganized Tripodal Urea Ligand 下载免费PDF全文
Dr. Komala Pandurangan Dr. Jonathan A. Kitchen Dr. Salvador Blasco Dr. Elaine M. Boyle Bella Fitzpatrick Dr. Martin Feeney Prof. Paul E. Kruger Prof. Thorfinnur Gunnlaugsson 《Angewandte Chemie (International ed. in English)》2015,54(15):4566-4570
The design and synthesis of tripodal ligands 1 – 3 based upon the N‐methyl‐1,3,5‐benzenetricarboxamide platform appended with three aryl urea arms is reported. This ligand platform gives rise to highly preorganized structures and is ideally suited for binding SO42? and H2PO4? ions through multiple hydrogen‐bonding interactions. The solid‐state crystal structures of 1 – 3 with SO42? show the encapsulation of a single anion within a cage structure, whereas the crystal structure of 1 with H2PO4? showed that two anions are encapsulated. We further demonstrate that ligand 4 , based on the same platform but consisting of two bis‐urea moieties and a single ammonium moiety, also recognizes SO42? to form a self‐assembled capsule with [4:4] SO42?: 4 stoichiometry in which the anions are clustered within a cavity formed by the four ligands. This is the first example of a self‐sorting self‐assembled capsule where four tetrahedrally arranged SO42? ions are embedded within a hydrophobic cavity. 相似文献
24.
Double O-H insertion reactions of cyclic diazo amides 1 and dihydroxy compounds 2 in the presence of rhodium(II) acetate catalyst have been achieved, which ultimately led to the facile synthesis of prototype bis(3-oxy-1,3-dihydro-2H-indol-2-one) systems. This facile double O-H insertion reaction protocol was successfully applied to synthesize several C2-symmetric macrocycles having oxindole units incorporated with complete diastereoselectivity. 相似文献
25.
Pandurangan Subash-Babu Hussah Mohammed Alowaidh Laila Naif Al-Harbi Ghalia Shamlan Amal A. Aloud Sahar Abdulaziz AlSedairy Ali Abdullah Alshatwi 《Molecules (Basel, Switzerland)》2022,27(4)
Excessive storage of lipids in visceral or ectopic sites stimulates adipokine production, which attracts macrophages. This process determines the pro- and anti-inflammatory response regulation in adipose tissue during obesity-associated systemic inflammation. The present study aimed to identify the composition of Ocimum basilicum L. (basil) seed extract and to determine its bio-efficacy on adipocyte thermogenesis or fatty acid oxidation and inhibition of lipid accumulation and adipokine secretion. Ocimum basilicum L. seed methanol extract (BSME) was utilized to analyze the cytotoxicity vs. control; lipid accumulation assay (oil red O and Nile red staining), adipogenesis and mitochondrial-thermogenesis-related gene expression vs. vehicle control were analyzed by PCR assay. In addition, vehicle control and BSME-treated adipocytes condition media were collected and treated with lipopolysaccharide (LPS)-induced macrophage to identify the macrophage polarization. The results shown that the active components present in BSME did not produce significant cytotoxicity in preadipocytes or macrophages in the MTT assay. Furthermore, oil red O and Nile red staining assay confirmed that 80 and 160 μg/dL concentrations of BSME effectively arrested lipid accumulation and inhibited adipocyte maturation, when compared with tea polyphenols. Gene expression level of adipocyte hyperplasia (CEBPα, PPARγ) and lipogenesis (LPL)-related genes have been significantly (p ≤ 0.05) downregulated, and mitochondrial-thermogenesis-associated genes (PPARγc1α, UCP-1, prdm16) have been significantly (p ≤ 0.001) upregulated. The BSME-treated, maturing, adipocyte-secreted proteins were detected with a decreased protein level of leptin, TNF-α, IL-6 and STAT-6, which are associated with insulin resistance and macrophage recruitment. The “LPS-stimulated macrophage” treated with “BSME-treated adipocytes condition media”, shown with significant (p ≤ 0.001) decrease in metabolic-inflammation-related proteins—such as PGE-2, MCP-1, TNF-α and NF-κB—were majorly associated with the development of foam cell formation and progression of atherosclerotic lesion. The present findings concluded that the availability of active principles in basil seed effectively inhibit adipocyte hypertrophy, macrophage polarization, and the inflammation associated with insulin resistance and thrombosis development. Ocimum basilicum L. seed may be useful as a dietary supplement to enhance fatty acid oxidation, which aids in overcoming metabolic complications. 相似文献
26.
Canonical labeling of a graph consists of assigning a unique label to each vertex such that the labels are invariant under isomorphism. Such a labeling can be used to solve the graph isomorphism problem. We give a simple, linear time, high probability algorithm for the canonical labeling of a G(n,p) random graph for p[ω(ln4n/nlnlnn),1−ω(ln4n/nlnlnn)]. Our result covers a gap in the range of p in which no algorithm was known to work with high probability. Together with a previous result by Bollobás, the random graph isomorphism problem can be solved efficiently for p[Θ(lnn/n),1−Θ(lnn/n)]. 相似文献
27.
This article reports direct electrocatalytic oxidation of cysteine (CySH) and cystine (CyS‐SCy) at an inexpensive Nafion/lead oxide‐manganese oxide combined catalyst in physiological pH. The synthesized lead oxide‐manganese oxide material is simply mixed with Nafion in the form of cast solution and modified on a disposable screen‐printed carbon electrode (designated as SPE/Nf‐PMO) for biosensing application. Electrochemical study with a standard redox couple of quinone/hydroquinone demonstrates an enhanced current response at the combined catalyst compared to its individual component. Surface characterization further provides information regarding the structural morphology of the catalyst to its catalytic performance. Direct electrocatalytic oxidation signals are observed at +0.75 and +1.20 V vs. Ag/AgCl for cysteine and cystine, respectively, at the SPE/Nf‐PMO. To extend the applicability, we further apply the proposed system for the detection of cysteine and cystine by flow injection analysis (FIA). Under optimized conditions, the detection limit (S/N=3) is 0.43 μM and 0.33 μM for cysteine and cystine, respectively. 相似文献
28.
Dr. Komala Pandurangan Brendan Gildea Dr. Caroline Murray Dr. Charles J. Harding Dr. Helge Müller‐Bunz Dr. Grace G. Morgan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(7):2021-2029
Six solvated salts of a mononuclear manganese(III) complex with a chelating hexadentate Schiff base ligand are reported. One member of the series, [MnL]PF6.0.5 CH3OH ( 1 ), shows a rare low‐spin (LS) electronic configuration between 10–300 K. The remaining five salts, [MnL]NO3? C2H5OH ( 2 ), [MnL]BF4?C2H5OH ( 3 ), [MnL]CF3SO3?C2H5OH ( 4 ), [MnL]ClO4?C2H5OH ( 5 ) and [MnL]ClO4?0.5 CH3CN ( 6 ), all show gradual incomplete spin‐crossover (SCO) behaviour. The structures of all were determined at 100 K, and also at 293 K in the case of 3 – 6 . The LS salt [MnL]PF6.0.5 CH3OH is the only member of the series that does not exhibit strong hydrogen bonding. At 100 K two of the four SCO complexes ( 2 and 4 ) assemble into 1D hydrogen‐bonded chains, which weaken or rupture on warming. The remaining SCO complexes 3 , 5 and 6 do not form 1D hydrogen‐bonded chains, but instead exhibit discrete hydrogen bonding between cation/counterion, cation/solvent or counterion/solvent and show no significant change on warming. 相似文献
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30.
M. Adharvana Chari A. Pandurangan B. Sathyaseelan S.M. Javaid Zaidi 《Tetrahedron letters》2010,51(19):2629-6112
Mesoporous Aluminosilicate (AlKIT-5) has been found to be an efficient catalyst for one-pot synthesis of triazolo[1,2-a]indazole-1,3,8-trione derivatives from dimedone, urazole, and aromatic aldehydes using acetonitrile as a solvent. This new method is simple, effective, ecofriendly, and consistently has the advantage of excellent yields (80-96%) and short reaction time (30-60 min). The effect of the catalyst weight, aluminum content in the catalyst, and the solvents on the synthesis of triazolo[1,2-a]indazole-1,3,8-trione derivatives has been investigated. It has been found that the catalyst can be recycled for several times without much affecting its activity for a variety of organic transformations. 相似文献