Tag: M.W:300-400

The reaction rate of a catalyzed reaction is faster than the reaction rate of the uncatalyzed reaction at the same temperature.14187-32-7, Name is Dibenzo-18-crown-6, molecular formula is C20H24O6. In a Article，once mentioned of 14187-32-7, Product Details of 14187-32-7

The mechanism of facilitated membrane transport of salts through supported liquid membranes containing synthetic ionophores in o-nitrophenyl octyl ether has been studied with potassium perchlorate and dibenzo-18-crown-6.As a support the microporous polypropylene membranes Accurel and Celgard 2500 were tested.The diffusion of the crown ether and crown ether complex through the membrane phase depends only on the porosity of the membrane for Accurel and on the porosity as well as the tortuosity of the membrane for Celgard 2500.The transport rate is determined by diffusion of the crown ether complex through the membrane phase.Measurements of the flux as a function of the initial salt concentration show that the cation-crown ether complex and the anion are present in the membrane phase predominantly as free ions.The partition coefficient of dibenzo-18-crown-6 for the system o-nitrophenyl octyl ether/water has been determined to be 1920 +/- 370 but due to the large ratio of aqueous to membrane volume (VW/Vm = 1200), at equilibrium 40 molpercent of the initial carrier concentration is present in the aqueous phases.From the effect of carrier concentration on the flux it was concluded that in the membrane an average fraction of crown ether of 0.35 +/- 0.07 is complexed to a cation.

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Chiral Catalysts,
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Synthetic Route of 14187-32-7, Children learn through play, and they learn more than adults might expect. Science experiments are a great way to spark their curiosity, get their minds active, and encourage them to do something that doesn’t involve a screen. 14187-32-7, C20H24O6. A document type is Article, introducing its new discovery.

The fullerene-crown ether conjugates (±)-1 to (±)-3 with trans-1 ((±)-1), trans-2 ((±)-2), and trans-3 ((±)-3) addition patterns on the C- sphere were prepared by Bingel macrocyclization. The trans-1 derivative (±)- 1 was obtained in 30% yield, together with a small amount of (±)-2 by cyclization of the dibenzo[18]crown-6(DB18C6)-tethered bis-malonate 4 with C60 (Scheme 1). When the crown-ether tether was further rigidified by K+- ion complexation, the yield and selectivity were greatly enhanced, and (±)-1 was obtained as the only regioisomer in 50% yield. The macrocyclization, starting from a mixture of tethered bis-malonates with anti (4) and syn (10) bisfunctionalized DB18C6 moieties, afforded the trans-1 ((±)-1, 15%), trans- 2 ((±)-2, 1.5%), and trans-3 ((±)-3, 20%) isomers (Scheme 2). Variable- temperature 1H-NMR (VT-NMR) studies showed that the DB18C6 moiety in C2- symmetrical (±)-1 cannot rotate around the two arms fixing it to the C- sphere, even at 393 K. The planar chirality of (±)-1 was confirmed in 1H- NMR experiments using the potassium salts of (S)1,1′-binaphthalene-2,2′-diyl phosphate ((±)-(S)-19) or (+)-(1S)-camphor-10-sulfonic acid ((+)-20) as chiral shift reagents (Fig. 1). The DB18C6 tether in (±)-1 is a true covalent template: it is readily removed by hydrolysis or transesterification, which opens up new perspectives for molecular scaffolding using trans-1 fullerene derivatives. Characterization of the products 11 (Scheme 3) and 18 (Scheme 4) obtained by tether removal unambiguously confirmed the trans-1 addition pattern and the out-out geometry of (±)-1. VT-NMR studies established that (±)-2 is a C2-symmetrical out- out trans-2 and (±)-3 a C1-symmetrical in-out trans-3 isomer. Upon changing from (±)-1 to (±)-3, the distance between the DB18C6 moiety and the fullerene surface increases and, correspondingly, rotation of the ionophore becomes increasingly facile. The ionophoric properties of (±)-1 were investigated with an ion-selective electrode membrane (Fig. 2 and Table 2), and K+ was found to form the most stable complex among the alkali-metal ions. The complex between (±)-1 and KPF6 was characterized by X-ray crystal-structure analysis (Figs. 3 and 4), which confirmed the close tangential orientation of the ionophore atop the fullerene surface. Addition of KPF6 to a solution of (±)-1 resulted in a large anodic shift (90 mV) of the first fullerene-centered reduction process, which is attributed to the electrostatic effect of the K- ion bound in close proximity to the C-sphere (Fig. 5). Smaller anodic shifts were measured for the KPF6 complexes of (±)-2 (50 mV) and (±)-3 (40 mV), in which the distance between ionophore and fullerene surface is increased (Table 3). The effects of different alkali- and alkaline-earth-metal ion salts on the redox properties of (±)-1 were investigated (Table 4). These are the first-ever observed effects of cation complexation on the redox properties of the C-sphere in fullerene- crown ether conjugates.

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Chiral Catalysts,
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14187-32-7, Name is Dibenzo-18-crown-6, molecular formula is C20H24O6, belongs to chiral-catalyst compound, is a common compound. In a patnet, once mentioned the new application about 14187-32-7, Product Details of 14187-32-7

Definitive X-ray structures of “separated” versus “contact” ion pairs, together with their spectral (UV-NIR, ESR) characterizations, provide the quantitative basis for evaluating the complex equilibria and intrinsic (self-exchange) electron-transfer rates for the potassium salts of p-dinitrobenzene radical anion (DNB-). Three principal types of ion pairs, K(L)+DNB-, are designated as Classes S, M, and C via the specific ligation of K+ with different macrocyclic polyether ligands (L). For Class S, the self-exchange rate constant for the separated ion pair (SIP) is essentially the same as that of the “free” anion, and we conclude that dinitrobenzenide reactivity is unaffected when the interionic distance in the separated ion pair is r SIP ? 6 A. For Class M, the dynamic equilibrium between the contact ion pair (with rCIP = 2.7 A) and its separated ion pair is quantitatively evaluated, and the rather minor fraction of SIP is nonetheless the principal contributor to the overall electron-transfer kinetics. For Class C, the SIP rate is limited by the slow rate of CIP ? SIP interconversion, and the self-exchange proceeds via the contact ion pair by default. Theoretically, the electron-transfer rate constant for the separated ion pair is well-accommodated by the Marcus/Sutin two-state formulation when the precursor in Scheme 2 is identified as the “separated” inner-sphere complex (ISSIP) of cofacial DNB-/DNB dyads. By contrast, the significantly slower rate of self-exchange via the contact ion pair requires an associative mechanism (Scheme 3) in which the electron-transfer rate is strongly governed by cationic mobility of K(L)+ within the “contact” precursor complex (ISCIP) according to the kinetics in Scheme 4.

Balanced chemical reaction does not necessarily reveal either the individual elementary reactions by which a reaction occurs or its rate law.Product Details of 14187-32-7. In my other articles, you can also check out more blogs about 14187-32-7

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Chiral Catalysts,
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The reaction rate of a catalyzed reaction is faster than the reaction rate of the uncatalyzed reaction at the same temperature.14187-32-7, Name is Dibenzo-18-crown-6, molecular formula is C20H24O6. In a Article，once mentioned of 14187-32-7, SDS of cas: 14187-32-7

New crystalline materials of mixed composition based on the interaction between tetraarylporphyrin and 18-crown-6 derivatives have been prepared and characterized by X-ray diffraction analysis. Free crown ether macrocycles (18- crown-6 and dibenzo-18-crown-6) associate to manganese- or zinc- tetraphenylporphyrin in aqueous solution through a bridging molecule of water which simultaneously coordinates to the axial site of the porphyrin metal core and hydrogen bonds to the oxygens of the crown ether. This ternary mode of self- assembly can lead to the formation of monomeric, oligomeric and stacked polymeric entities, depending on the symmetry of the crown structure and the preferred coordination geometry of the metal ion. Sodium or potassium 18-crown- 6 chlorides were found to be excellent templates for the construction of non- interpenetrating beta-molecular networks from zinc-tetra(4- carboxyphenyl)porphyrin building blocks. The resulting layered motifs incorporate the crown ether moieties within the interporphyrin cavities. These arrays are stabilized by strong hydrogen bonds between the self-complementary carboxylic groups as well as by ion pairing, as their formation is associated with proton transfer from one of the carboxylic groups to the chloride anion and expulsion of hydrochloric acid. Molecules of the methanol solvent, which coordinate axially to the central metal ions of the porphyrin and crown ether moieties in one layer while hydrogen bonding to the carboxylic groups of another layer, contribute to the tight packing of the molecular layers along the third dimension. The experimentally established geometries and packing modes of these aggregates provide useful information for further crystal engineering efforts of networked multi-porphyrin domains.

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Chiral Catalysts,
Chiral catalysts – SlideShare

Related Products of 39648-67-4, Chemistry can be defined as the study of matter and the changes it undergoes. You’ll sometimes hear it called the central science because it is the connection between physics and all the other sciences, starting with biology.39648-67-4, Name is (R)-4-Hydroxydinaphtho[2,1-d:1′,2′-f][1,3,2]dioxaphosphepine 4-oxide, molecular formula is C20H13O4P. In a patent, introducing its new discovery.

An efficient and transition-metal-free approach was developed to access a series of fluorinated heteroaromatics in moderate to excellent yields. This one-pot procedure features a triple-relay transformation of rapid dearomatization, fluorination, and rearomatization processes, which represents a conceptually novel strategy of combining partial hydrogenation and electrophilic fluorination.

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Chiral Catalysts,
Chiral catalysts – SlideShare

The reaction rate of a catalyzed reaction is faster than the reaction rate of the uncatalyzed reaction at the same temperature.39648-67-4, Name is (R)-4-Hydroxydinaphtho[2,1-d:1′,2′-f][1,3,2]dioxaphosphepine 4-oxide, molecular formula is C20H13O4P. In a Article，once mentioned of 39648-67-4, HPLC of Formula: C20H13O4P

Optically pure 2-(quinolin-8-yloxy)cyclohexan-1-ol 1, obtained via simple chemical and bio-catalytic steps, was used as a chiral solvating agent for molecular recognition of the enantiomers of acids. The discrimination of isomers was detected by NMR or fluorescence spectroscopy. Isomers of alpha-substituted carboxylic acids, phosphoric acids, unprotected amino acids and dipeptides were efficiently detected, while the method can be used for quantitative determination for practical applications. Analysis of the crystal of (R,R)-1 (R)-mandelic acid established a three point supramolecular interaction.

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Chiral Catalysts,
Chiral catalysts – SlideShare

Electric Literature of 39648-67-4. Let’s face it, organic chemistry can seem difficult to learn. Especially from a beginner’s point of view. Like 39648-67-4, Name is (R)-4-Hydroxydinaphtho[2,1-d:1′,2′-f][1,3,2]dioxaphosphepine 4-oxide. In a document type is Article, introducing its new discovery.

A Br°nsted acid/Lewis acid dual catalyst system was developed to promote efficient C-C bond formation between a range of oxocarbenium precursors derived from chromene acetals and ethyl diazoacetate. The reaction proceeds under mild conditions and is tolerant of functionalized 2H-chromenes and isochromene acetals. In addition, an asymmetric variant of diazoacetate addition towards 2H-chromene acetals is described. Continued investigations include further optimization of asymmetric induction towards the formation of diazo ester substituted 2H-chromene.

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Chiral Catalysts,
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Related Products of 39648-67-4, An article , which mentions 39648-67-4, molecular formula is C20H13O4P. The compound – (R)-4-Hydroxydinaphtho[2,1-d:1′,2′-f][1,3,2]dioxaphosphepine 4-oxide played an important role in people’s production and life.

Novel macrocyclic compounds, synthesized and used as chiral solvating agents for phosphinic, phosphonic, and phosphoric acids, are reported in this article. NMR (1H NMR and/or 31P NMR) studies demonstrate that these acids have large nonequivalent chemical shifts in the presence of these macrocyclic compounds. Quantitative analyses of a series of the selected phosphinic acids with different enantiomeric purities show the high accuracy of this method.

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Chiral Catalysts,
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Application of 14187-32-7, An article , which mentions 14187-32-7, molecular formula is C20H24O6. The compound – Dibenzo-18-crown-6 played an important role in people’s production and life.

Raman and IR spectra of 18-crown-6 with cations were measured for their aqueous solutions and crystals.A Cs symmetry conformation of 18-crown-6 in its complexes with divalent cations was deduced, based on the solvent effect on the spectra of 18-crown-6 and also normal vibration calculation.Conformation analyses by spectral patterns revealed that the electric charge of captured cations determines the conformation of 18-crown-6 in complexes in solutions, while that of the crystals is affected by the ionic diameter of captured cations.

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Chiral Catalysts,
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Reference of 14187-32-7, Catalysts are substances that increase the reaction rate of a chemical reaction without being consumed in the process. 14187-32-7, Name is Dibenzo-18-crown-6, molecular formula is C20H24O6. In a Article，once mentioned of 14187-32-7

The products of the reactions between potassium hexachloroplatinate [K2PtCl6] and 18-crown-6 or dibenzo-18-crown-6 in acetonitrile were studied. Pure crystalline compounds [2K·2(18-crown-6)· 2CH3CN]2+ · [PtCl6]2- · 2H2O, [2K · dibenzo-18-crown-6 · CH3CN]2+ · [PtCl6]2-, and [2K · dibenzo-18-crown-6 · CH3CN]2+ · [Pt2Cl10]2- were obtained. Physicochemical properties of these compounds were studied, and their near- and far-IR IR spectra and thermogravimetric curves were considered. The composition of the complexes is determined by metal : ligand molar ratio and crown ether nature. It was found that acetonitrile is coordinated via the nitrogen atom.

The proportionality constant is the rate constant for the particular unimolecular reaction. the reaction rate is directly proportional to the concentration of the reactant. I hope my blog about 14187-32-7 is helpful to your research., Reference of 14187-32-7

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Chiral Catalysts,
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