Category: 14187-32-7

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, Computed Properties of C20H24O6

Microhydration of Dibenzo-18-Crown-6 Complexes with K+, Rb+, and Cs+ Investigated by Cold UV and IR Spectroscopy in the Gas Phase

In this Article, we examine the hydration structure of dibenzo-18-crown-6 (DB18C6) complexes with K+, Rb+, and Cs+ ion in the gas phase. We measure well-resolved UV photodissociation (UVPD) spectra of K+¡¤DB18C6¡¤(H2O)n, Rb+¡¤DB18C6¡¤(H2O)n, and Cs+¡¤DB18C6¡¤(H2O)n (n = 1-8) complexes in a cold, 22-pole ion trap. We also measure IR-UV double-resonance spectra of the Rb+¡¤DB18C6¡¤(H2O)1-5 and the Cs+¡¤DB18C6¡¤(H2O)3 complexes. The structure of the hydrated complexes is determined or tentatively proposed on the basis of the UV and IR spectra with the aid of quantum chemical calculations. Bare complexes (K+¡¤DB18C6, Rb+¡¤DB18C6, and Cs+¡¤DB18C6) have a similar boat-type conformation, but the distance between the metal ions and the DB18C6 cavity increases with increasing ion size from K+ to Cs+. Although the structural difference of the bare complexes is small, it highly affects the manner in which each is hydrated. For the hydrated K+¡¤DB18C6 complexes, water molecules bind on both sides (top and bottom) of the boat-type K+¡¤DB18C6 conformer, while hydration occurs only on top of the Rb+¡¤DB18C6 and Cs+¡¤DB18C6 complexes. On the basis of our analysis of the hydration manner of the gas-phase complexes, we propose that, for Rb+¡¤DB18C6 and Cs+¡¤DB18C6 complexes in aqueous solution, water molecules will preferentially bind on top of the boat conformers because of the displaced position of the metal ions relative to DB18C6. In contrast, the K+¡¤DB18C6 complex can accept H2O molecules on both sides of the boat conformation. We also propose that the characteristic solvation manner of the K+¡¤DB18C6 complex will contribute entropically to its high stability and thus to preferential capture of K+ ion by DB18C6 in solution.

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Syntheses of cis- and trans-dibenzo-30-crown-10 derivatives via regioselective routes and their complexations with paraquat and diquat

(Chemical Equation Presented) cis-Dibenzo-30-crown-10 (cis-DB30C10) diester and trans-dibenzo-30-crown-10 (trans-DB30C10) diester were synthesized regioselectively with reasonable yields. These two isomers were further reduced to cis-dibenzo-30-crown-10 diol (1) and trans-DB30C10 diol (2), respectively. The complexations of cis-and trans-DB30C10 diols with paraquat (3) and diquat (4) were investigated by 1H NMR, mass spectrometry, UV-vis spectroscopy, and single-crystal X-ray analysis. The reversible control of complexations of 1?3 and 2?3 by adding small molecules (KPF 6 and dibenzo-18-crown-6) was demonstrated by 1H NMR. The addition of 2 molar equiv of KPF6 is enough to dissociate 2?3 and 1?3 completely while the subsequent addition of 2 molar equiv of DB18C6 allows the two complexes to reform. However, 2 molar equiv of KPF6 cannot dissociate 1?4 and 2?4 completely. Because the DB30C10 cavity has a better geometry fit with paraquat 3 than with diquat 4, 4-based complexes have much higher association constants than the corresponding 3-based complexes. In the crystal structure of 1?4, the two hydroxymethyl groups of the crown ether 1 were joined by a “water bridge” to form a “supramolecular cryptand” while this kind of supramolecular cryptand structure was not observed in the crystal structure of 2?4. This is a possible reason for the increase in association constant from 2?4 (3.3 ¡Á 104 M-1) to 1?4 (5.0 ¡Á 104 M-1).

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Self-assembled Structure of Inorganic-Organic Hybrid Crystals Based on Keggin Polyoxometallates [SMo12O402-] and Supramolecular Cations

To investigate the network structure of inorganic-organic hybrid crystals, we synthesized a series of assemblies based on polyoxometallates (POMs) [SMo12O402-] and different supramolecular cations consisting of anilinium and crown ether derivatives. The compounds [(m-XAni+)(B[18]crown-6)]2[SMo12O402-] (Ani+ = anilinium; B[18]crown-6 = benzo[18]crown-6; X = F (1), Cl (2), Br (3), or I (4)), [(4-MeAni+)(B[18]crown-6)]2[SMo12O402-]¡¤CH3CN (5), [(4-MeAni+)(DB[18]crown-6)]2[SMo12O402-]¡¤2CH3CN (6), [(3-F-4-MeAni+)(DB[18]crown-6)]2[SMo12O402-]¡¤2CH3CN (7), and [(3-F-4-MeAni+)2(DB[30]crown-10)][SMo12O402-]¡¤2CH3CN (8) (4-MeAni+ = 4-methylanilinium; DB[18]crown-6 = dibenzo[18]crown-6; 3-F-4-MeAni+ = 3-fluoro-4-methylanilinium; DB[30]crown-10 = dibenzo[30]crown-10) were synthesized. Their crystal architectures were characterized according to the size and charge of the supramolecular cations. In 1-4, two adjacent supramolecular cations ([(m-XAni+)(B[18]crown-6)]) were connected through pi?pi interactions forming sandwich-type dimers with the cations that were stacked in an antiparallel manner. In 8, DB[30]crown-10 included two cations constructing a larger divalent supramolecular cation [(3-F-4-MeAni+)2(DB[30]crown-10)]. In 1-4 and 8, the ratio between [SMo12O402-] and the supramolecular cations was 1:1, and the latter formed rectangular-assembled structures. In 5, the pi?pi stacking interaction was present in the adjacent B[18]crown-6. Monovalent supramolecular cations were present in 5-7 with a ratio of 1:2 between [SMo12O402-] and the supramolecular cations. The supramolecular cations formed hexagonal-assembled structures.

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Probing supramolecular complexation of cetylpyridinium chloride with crown ethers

Supramolecular complexations of cetylpyridinium chloride with three comparable cavity dimension based crown ethers, namely, dibenzo-18-crown-6, 18-crown-6 and dicyclohexano-18-crown-6 have been explored and adequately compared in acetonitrile with the help of conductivity in a series of temperatures to reveal the stoichiometry of the three host-guest complexes. Programme based mathematical treatment of the conductivity data affords association constants for complexations from which the thermodynamic parameters were derived for better comprehension about the process. The interactions at molecular level have been explained and decisively discussed by means of FT-IR and 1H NMR spectroscopic studies that demonstrate H-bond type interactions as the primarily force of attraction for the investigated supramolecular complexations.

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Macrocyclic Receptor Molecules for Guanidinium Cations. Preparation, X-ray Structures, and Kinetic Stabilities of 1:1 Complexes of Guanidinium Perchlorate with Benzo-27-crown-9, Dibenzo-27-crown-9, and Dibenzo-30-crown-10

The complexation of guanidinium perchlorate with crown ethers of different ring size (18-33 ring atoms) and with different subunits, e.g., catechol and 1,3-xylyl moities, has been studied by using two-phase extraction experiments.The results demonstrate that the 18-crown ethers are able to form perching complexes, whereas crown ethers with <*>27 ring atoms have a siutable ring size to form encapsulated complexes with guanidinium perchlorate.Aromatic, catechol, and especially 1,3-xylyl moieties have a destabilizing effect on the complex formation.The crystal and the molecular structures of the 1:1 complexes of guanidinium perchlorate with benzo-27-crown-9 (7), dibenzo-27-crown-9 (8), and dibenzo-30-crown-10 (11) have been determined by X-ray crystallography.In these encapsulated complexes all hydrogen atoms of the guanidinium cation are used in hydrogen bonds to the macrocyclic host.The 27-crown ethers show an optimal fit between cation and the macrocyclic host with a complementary binding scheme.Dynamic 500-MHz (1)H NMR spectroscopy gave the kinetic stabilities of these complexes with DeltaGd* values of 11.5, 11.2, and 12.0 kcal mol-1 for the complexes with benzo-17-crown-9, dibenzo-27-crown-9, and dibenzo-30-crown-10, respectively.

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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, Safety of Dibenzo-18-crown-6

Influence of Polyethers on Properties of Aluminum Dust

A study was made of the dispersing and modifying action of perfluorinated oligopropylene oxide and dibenzo-18-crown-6 ether on aluminum powders being milled in a ball mill used for preparing highly reactive powders.

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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, Recommanded Product: 14187-32-7

Microhydration effects on the encapsulation of potassium ion by dibenzo-18-crown-6

We have measured electronic and conformer-specific vibrational spectra of hydrated dibenzo-18-crown-6 (DB18C6) complexes with potassium ion, K +?DB18C6?(H2O)n (n = 1-5), in a cold, 22-pole ion trap. We also present for comparison spectra of Rb +?DB18C6?(H2O)3 and Cs +?DB18C6?(H2O)3 complexes. We determine the number and the structure of conformers by analyzing the spectra with the aid of quantum chemical calculations. The K +?DB18C6?(H2O)1 complex has only one conformer under the conditions of our experiment. For K +?DB18C6?(H2O)n with n = 2 and 3, there are at least two conformers even under the cold conditions, whereas Rb+?DB18C6?(H2O)3 and Cs +?DB18C6?(H2O)3 each exhibit only one isomer. The difference can be explained by the optimum matching in size between the K+ ion and the crown cavity; because the K+ ion can be deeply encapsulated by DB18C6 and the interaction between the K+ ion and the H2O molecules becomes weak, different kinds of hydration geometries can occur for the K+?DB18C6 complex, giving multiple conformations in the experiment. For K+?DB18C6?(H 2O)n (n = 4 and 5) complexes, only a single isomer is found. This is attributed to a cooperative effect of the H2O molecules on the hydration of K+?DB18C6; the H2O molecules form a ring, which is bound on top of the K+?DB18C6 complex. According to the stable structure determined in this study, the K + ion in the K+?DB18C6?(H2O) n complexes tends to be pulled largely out from the crown cavity by the H2O molecules with increasing n. Multiple conformations observed for the K+ complexes will have an advantage for the effective capture of the K+ ion over the other alkali metal ions by DB18C6 because of entropic effects on the formation of hydrated complexes.

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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, Application In Synthesis of Dibenzo-18-crown-6

Synthesis and complexing property of four-bridged crownopaddlanes

A new series of crown compounds crownopaddlanes 3a-c bearing three cyclobutane rings were prepared by means of intramolecular [2+2] photocycloaddition of styrene derivatives. The yield of crownopaddlane 3b possessing five ethereal oxygen atoms was remarkably high 52% with the addition of sodium borofluoride in the photoreaction system. As this template effect suggests, 3b showed extraordinarily high Na+-selectivity with high efficiency on the liquid-liquid extraction of alkali metal picrates, though 3a having four ethereal oxygen atoms did not extracted any cations in this system. The high Na+-selectivity of 3b was further clarified by the equilibrium stability constants (log Ka) for Na+ (5.85) and K+ (2.91) in acetonitrile solution. The complexation of 3b to Na+ cation was also examined by X-ray crystallography. Crownopaddlane 3c bearing six ethereal oxygen atoms also efficiently and selectively extracted alkali metal cations, compared with conventional 18-crown-6 derivatives.

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The Influence of Crown Ethers on Cation Migration Processes. Part 4. Some Simple Benzoquinone Radical Anions in the Presence of Dibenzo-18-crown-6

The radical anions of 2,5-di-t-butyl- and 2,5-dimethyl-benzoquinone have been prepared in 1,2-dimethoxyethane with Li+, Na+, or K+ as the counterion in the presence of dibenzo-18-crown-6.Linewidth alternation is observed in the e.s.r. spectra of these radical anions, with the lifetime of the counterion at one of the preferred sites near the radical anion varying in the sequence Li+ > Na+ > K+ at a particular temperature.It is apparent that in the presence of the crown ether ‘contact’ ion pairs are still present in the majority of the systems studied.The relatively minor influence of the crown ether on these systems is probably a result of the similarity in cation solvation environment presented by 1,2-dimethoxyethane and the crown ether.

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Reference of 14187-32-7, 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.14187-32-7, Name is Dibenzo-18-crown-6, molecular formula is C20H24O6. In a patent, introducing its new discovery.

Reactivity of tris(allyl)aluminum toward pyridine: Coordination versus carbometalation

Tris(allyl)aluminum as its THF adduct, [Al(eta1-C 3H5)3(THF)] (1), reacted with pyridine either under substitution to give [Al(eta1-C3H 5)3(py)] (7) (py = pyridine) or under carbometalation to give N-metalated 2-allyldihydropyridine depending on the solvent. The substituent pattern of the pyridine substrate and the aluminum center’s electrophilicity in [Al(eta1-C3H5) 3(L)] (L = neutral ligand) influenced the outcome of the reaction. Reactions of one N-metalated dihydropyridine with electrophiles have been studied. A crystalline derivative of tris(allyl)aluminum, [Al(eta1- C3H5)3(OPPh3)] (2), and tetrakis(allyl)aluminate in the ion pair [K(15-crown-5)2] [Al(eta1-C3H5)4] (4) were characterized by single-crystal X-ray diffraction and shown to contain four-coordinate aluminum centers.

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