The conductivity of non-aqueous electrolyte solutions containing crown-ethers

The conductance of NaI and RbI in acetonitrile solutions at 25°C in presence of different crown-ethers was measured. Analysis of the data in pure acetonitrile and in presence of the crown compounds was carried out using the Fuoss-Onsager-Skinner equations. Addition of crown ethers to the salt solutions generates a decrease in the conductivity in the order of 12-crown-4 < 15-crown-5 < 18-crown-6 < disubstituted 18-crown-6. The difference between the Λ₀ values of the two systems investigated with the same crown compounds decreases as the complexity of the crown-ether used increases. The results, also compared to those of KI systems, are discussed in terms of competitive interaction forces of the crown-ethers and the solvent molecules on the ionic species present in solution.     

煤慢速升温热解过程中冠醚对硫脱除率的影响

在固定床反应器中研究了团柏煤中硫在氮气气氛下随温度、停留时间的变迁规律,并考察了煤慢速升温热解过程中添加18-冠-6或二苯并-18-冠-6对硫脱除率的影响。结果表明:在煤热解过程中添加18-冠-6或二苯并-18-冠-6都有利于总硫的脱除;当热解温度大于550℃时,相同条件下添加二苯并-18-冠-6时总硫的脱除效果明显优于添加18-冠-6;在煤热解过程中,添加二苯并-18-冠-6也可提高有机硫的脱除率;当热解温度小于650℃时,添加18-冠-6或二苯并-18-冠-6,同时可明显提高黄铁矿硫的脱除率。通过对热解半焦进步的脱附实验和孔结构分析,发现在原煤热解过程中,添加18-冠-6或二苯并-18-冠-6,可以使半焦平均孔径变大。     

Conductance study of ion-pairing of alkali tetrafluoroborates and hexafluorophosphates in acetonitrile containing some substituted macrocyclic polyethers

The conductance of sodium and potassium tetrafluoroborates and hexafluorophosphates in acetonitrile solutions at 25°C in the presence of bis(4-tert-butylbenzo)-18-crown-6(mtbDBC), bis(3,5-di-tert-butylbenzo)-18-crown-6 (dtbDBC) and bis(4-hexadecylbenzo)-18-crown-6 (hdDBC) has been investigated. The analysis of data has been performed by means of the Fuoss—Hsia conductance equation. Values of the limiting conductance, Λ₀, and ion-pair dissociation constants, K_D, are reported. The results obtained are compared with those obtained for the conductance of sodium and potassium tetrafluoroborates and hexafluorophosphates in pure acetonitrile. Addition of macrocyclic polyethers in the salt solutions gives a decrease in the conductivity in the order dtbDBC < mtbDBC < hdDBC. All systems were found to be associated, and the trends in association are discussed in terms of the polyether interactions with alkali cation which are controlled by their size, the steric hindrance effects caused by the alkyl substituents in the polyether molecule, size and charge density of the anion, and the interaction forces of the solvent molecules on the ionic species present in solution.     

Effect of Ring-Size Variation within Dibenzocrown Ether Resins upon Ion-Pair Sorption of Alkali-Metal Cations from Aqueous and Aqueous Methanol Solutions

Abstract

A batch analysis method has been developed for evaluation of metal salt sorption by crown ether polymers. Selectivity in competitive alkali-metal chloride sorption by a series of formaldehyde condensation polymers of dibenzocrown ethers is influenced by the relationship between the crown ether cavity size and metal ion diameter, as well as the degree of hydration of the metal salt. Effective and selective sorption of KCl from the other alkali-metal chlorides was obtained with a dibenzo-18-crown-6 resin. Excellent sorption selectivity for the monovalent metal chlorides was noted for competitive ion-pair sorption of NaCl, KCl, MgCl₂, and CaCl₂ by this resin. This resin was examined as a stationary phase for selective column separation of KCl from alkali-metal chlorides and of KCl and NaCl from alkali-metal and alkaline-earth chloride mixtures in 80% methanol—20% water.     

Specific membrane transport of silver and copper as Ag(CN)3 and Cu(CN)4 ions through a supported liquid membrane using K-crown ether as a carrier

Facilitated transport of silver and copper from cyanide solutions through a supported liquid membrane (SLM) containing K⁺-crown ether as a carrier is described. The SLM used is a thin porous polypropylene (Celgard 2500, 2400) membrane impregnated with dibenzo-18-crown-6 (DB18C6), diaza-18-crown-6 (DA18C6), hexathia-18- crown-6 (HT18C6) and hexaaza-18-crown-6 (HA18C6) dissolved in a mixture of ethanol/chloroform (v/v). K₋⁺-crown ether showed a high efficiency to carry silver and copper as Ag(CN)₃²⁻ and Cu(CN)₄³⁻ species through the SLM. However, the mass flux of both silver and copper ions decreases when concentration of cyanide ions in the feed phase increases due to the difference in stability of the complexes M(CN)_nⁿ⁻(M=Ag, Cu) when n increases from 2 to 4. This was related to the partition of the species in the aqueous phase using a theoretical model.     

二甲酰基二苯并-18-冠-6的合成研究

利用Reimer-Tiemann及Vilsmeier反应原理,分别以二苯并-18-冠-6、三氯甲烷（CHCl3）和NaOH或者二苯并-18-冠-6、DMF和POCl3为原料,优化合成了二甲酰基二苯并18-冠-6,克服了直接酰基化使冠醚环断链等缺点,产品收率最高可达78.2%,并通过IR、^1HNMR及元素分析等方法对产物进行结构表征。     

Kinetics of Bromination of Stilbene in Chloroform in the Presence of a Macrocyclic Polyether

The effect of ethers on the bromination of stilbene in chloroform solutions was investigated spectrophotometrically. In the presence of hydrogen bromide the macrocyclic ether dicyclohexyl-18-crown-6 (DCC) may act as a strong inhibitor, while tetrahydrofuran accelerates the bromination reaction.     

Synthesis, Characterization and Thermogravimetric Analysis of Two Dicyclohexyl-18-crown-6 Pd, Pt Isomaleonitriledithiolate Complexes

Two organic–inorganic hybrid dicyclohexyl-18-crown-6 complexes, [K(DC18C6-B)]₂[Pd(i-mnt)₂] (1) and [K(DC18C6-A)]₂[Pt(i-mnt)₂] (2) (DC18C6-A=cis-syn-cis-dicyclohexyl-18-crown-6, A isomer; DC18C6-B = cis-anti-cis-dicyclohexyl-18-crown-6, B isomer; i-mnt=1,1-dicyanoethene-2,2-dithiolate, isomaleonitriledithiolate), were synthesized by the reaction of dicyclohexyl-18-crown-6 with K₂(i-mnt) and PdCl₂ or K₂PtCl₄ respectively. These were characterized by elemental analysis, FT–IR, UV–Vis spectroscopy and single crystal X-ray diffraction. In complex 1, two [K(DC18C6-B)]⁺ complex cations and one [Pd(i-mnt)₂]²⁻ complex anion formed a neutral molecule through two K–N coordination bonds. The resulting molecule adopted a 1D chain arrangement via K N weak interactions. Complex 2 showed a 1D chain-like structure that was assembled by two [K(DC18C6-A)]⁺ complex cations and one [Pt(i-mnt)₂]²⁻ complex anion through N–K–N interactions. An erratum to this article can be found at     

Creep Behavior of Potassium Chloride–Rubidium Chloride Solid Solution Alloys

The creep behavior of three KCl–RbCl solid solution alloys and pure KCl and pure RbCl single crystals compressed along the 〈100〉 direction was investigated at 600°C at stresses between 0.5 and 15 MPa. The reduced primary creep stage, a value of the stress exponent of about 3 for the KCl–20 mol% RbCl and KCl–30 mol% RbCl alloys versus about 5 for pure KCl and pure RbCl and the results of the stress reduction tests for these alloys are in good agreement with creep behavior observed in class I metallic solid solution alloys, where the creep rate is controlled by a dislocation glide process. The dislocation substructure developed in the KCl–RbCl alloys consisted of well-developed subgrains.     

Extraction of Radioactive Cs and Sr from Nitric Acid Solutions with 25,27-Bis(1-octyloxy)calix[4]-26,28-Crown-6 and Dicyclohexyl-18-Crown-6: Effect of Nature of the Organic Solvent

Extraction of microamounts of radioactive cesium and strontium by 25,27-bis(1-octyloxy)calix[4]-26,28-crown-6 (DOC[4]C6) and dicyclohexyl-18-crown-6 (DCH18C6) from nitric acidic solutions into alcohols, ketones and some other solvents was studied. We concentrated on collecting detailed data possibly useful for subsequent evaluations of appropriate schemes and mechanisms. Although not testing in fullness the system with DOC[4]C6 and DCH18C6 in 1-octanol, we present some evidence of its suitability such as fast kinetics, chemical and radiation stability, and invariance of parameters (process stability) after several times repeated batch extraction-strip cycles. Some peculiarities of a possible mechanism of extraction in these systems are reported.     

含二苯并-18-冠-6单元的酰胺型双臂冠醚化合物的合成

合成了２个含二苯并－１８－冠－６单元的酰胺型双臂冠醚化合物,其结构经ＩＲ、＾１ＨＮＭＲ、ＭＳ和元素分析确证,该２个化合物都不具有液晶性,探讨了冠醚结构与液晶性的关系。     

The coalescence of n-Hexane droplets in aqueous electrolyte solutions

Coalescence times, measured by high speed cinematography, are reported for n-hexane droplets formed on adjacent nozzles in pure water and in dilute aqueous solutions of the electrolytes KCl, KBr, KI, NaCl, and Na₂SO₄. Coalescence times in pure water were 17 + 11 ms, in satisfactory agreement with recent theories of Ivanov and of Reed, Riolo and Hartland. Coalescence times increased on addition of electrolytes, except for KI. Limiting values of coalescence times in electrolyte solutions could be accounted for by the theories of Marrucci. Thus the Marrucci parameter crk²/λ may be taken as a guide to droplet coalescence in solutions of solutes such as electrolytes which only change interfacial tensions slightly. The coalescence times are larger than for air-electrolyte solutions, largely because of the lower Hamaker-London attraction with the present system.     

冠醚化合物在制备外延卤化银乳剂中的作用

自从冠醚于六十年代末问世以来,科学家们对它进行了大量的研究。它以遮盖力大,对金属离子络合性能好而著称于化学领域。在感光化学领域,它的主要应用在于对乳剂晶体的尺寸及分布产生影响,使之均一,且颗粒增大;作为调变剂,促进外延乳剂晶体的生长;提高乳剂的感光性能。     

Stoichiometry and Structure of the Complexes Between Lanthanide Ions and Macrocyclic Crown Ethers Containing from Four to Seven Coordinating Sites

The factors influencing the stoichiometry and the structure of the complexes between trivalent lanthanide perchlorates, hexafluorophosphates, nitrates, trifluoroacetates, chlorides, bromides, isothiocyanates and the polyethers 12-crown-4, 15-crown-5, 18-crown-6, dibenzo-18-crown-6 and 21-crown-7 are reviewed. The properties of divalent lanthanide and Ce(IV) complexes with crown ethers are presented and discussed.     

Selective sorption of heavy metal thiocyanate complexes on crown ether resin

The sorption behavior of heavy metal thiocyanate complexes was investigated for dibenzo-18-crown-6 (DB18C6) resin and bis[2-(o-methoxyphenoxy)ethyl]ether (BMPE) resin. The DB18C6 resin showed a high sorption ability and the degree of zinc sorption increased significantly with thiocyanate concentration. This behavior was not observed for BMPE resin. The sorption behavior was influenced by the countercation species, and the degree of sorption of zinc ions showed the maximum when the potassium thiocyanate was used as a complexing salt. The sorbed species appear to be KZn(SCN)₃, K₂Zn(SCN)₄ in the potassium thiocyanate system, and Zn(SCN)₂ in the lithium thiocyanate system, respectively, according to analysis of the sorption equilibrium. Sodium and ammonium thiocyanate systems show an intermediate behavior of the two. The sorption selectivity for DB18C6 resin depended not only on the hydrophobic nature of heavy metal thiocyanate complexes but also on the stabilization of counter cation species with crown ether matrix, and the sorption selectively was found to be effectively controlled by countercation species according to the cation-chelation mechanism.     

THERMODYNAMICS OF COBALT(II) EXTRACTION BYTHENOYLTRIFLOUROACETONE AND DIBENZO-18-CROWN-6 IN NITROBENZENE-TOLUENE MIXTURES

Cobalt (II) was extracted by thenoyltrifluoroacetone (HTTA) and its mixture with dibenzo-18-crown-6(Dbl8C6) at different temperatures in nitrobenzene (Nb); toluene (Tol) or their mixtures, from perchlorate aqueous media of constant ionic strength (o.l;H⁺,NaClO₄) buffered with acetic acid-sodium acetate solutions. Slop analysis of the experimental results indicated that the stoichiometry of the chelate and the adduct extracted are Co(TTA)₂and Co(TTA)₂?Dbl8C6, under all the experimental conditions investigated. The extraction constants of the chelate (k₂o)’ tne mixed species (k_2land the formation constant of the adduct ( B_2lwere evaluated for the different diluents used at the different temperatures. It was found that log k_2oand log_2lincrease by increasing the dielectric constant (€ ) of the diluent whereby log B_2ldecreases by increasing €. These results were expressed in terms of linear free energy relationships. From the effect of the temperature on the different constants evaluated; the thermodynamic constants of the systems were calculated and discussed in terms of the nonspecific effect of the diluents used and the dehydration of the extracted chelate to form the adduct.     

SYNERGIC EXTRACTION OF COBALT(II) BY STRUCTURALLY RELATED CROWN ETHERS AND THENOYLTRIFLUOROACETONE

ABSTRACT

Cobalt (II) was extracted from perchlorate aqueous media by thenoyltrifluoroacetone (HTTA)alone and mixed with 12-Crown-4 (12C4) 15-Crown-5 (15C5) 18-Crown-6 (18C6)dibenzo-18-Crown-6 (Dbl8C6)dicyclohexyl-18-Crown-6 (Dchl8C6) or dicyclohexyl-24-Crown-8 (Dch24C8), in chloroform. The extraction constant of the chelate (K20) the extraction constant of the mixed species (K21), the synergic factor (S.F.) and the formation constant of the extracted adducts (β₂₁) were evaluated. The adduct stoichiometry was found to have the general formula Co(TTA)₂CE, irrespective of the crown ether (CE) used. It was found that no specific cavity size is required for the adduct formation. The synergic values K₂₁, S.F., and β₂₁as related to the crown ether took the order Dch24C8 > 18C6 > Dchl8C6 > 15C5 > Dbl8C6 > 12C4, which could be explained in terms of the crown ether basicity rather than the correspondence between the cavity size of the crown ether and the cobalt(II) crystal radii. The sequence 18C6 > Dchl8C6 > Dbl8C6 was interpreted in terms of the withdrawing ability of Dch and Db as substitutes in reducing the basic character of the adjacent crown ether oxygen donors.     

新型冠醚交联壳聚糖的合成

利用壳聚糖C2位上活泼氨基与苯甲醛反应,制得了保护氨基的Schiff碱壳聚糖（简称CTB）;再将合成的带有双活性基团的4,4‘-二溴二苯并18-冠-6冠醚与壳聚糖分子的羟基发生反应,得到二苯并18-冠-6冠醚交联的Schiff碱壳聚糖（简称CTBD）,在酸性条件下使CTBD脱去苯甲醛,制得二苯并18-冠-6冠醚交联壳聚糖（简称CTD）。其主要中间体及产物的结构经红外光谱、质谱、核磁共振动等进行了鉴定。     

Synthesis and self-assembly study of two-armed polymers containing crown ether core

Two functional crown ether initiator, bis[4′-(2-bromobutyryl)]dibenzo-18-crown-6 (BBDC) was synthesized through the condensation of dibenzo-18-crown-6 with 2-bromobutyric acid in the presence of polyphosphoric acid. Atom transfer radical polymerizations of styrene (St), methyl acrylate, methyl methacrylate and butyl acrylate were carried out in bulk to produce the polymers with well-controlled molecular weights and narrow molecular weight distributions (1.12-1.32). Based on ¹H NMR results, both the two bromides of BBDC initiated the polymerizations. The well-defined two-armed polymers were self-assemblized in the presence of potassium cations. Their morphologies of the film obtained were studied by atomic force microscopy with tapping mode.     

Silver complexes with large crown ethers in propylene carbonate

The complex formation between large crown ethers – e.g. dibenzo-30-crown-10 – and Ag⁺ in propylene carbonate has been studied using potentiometric and calorimetric titrations. The values of the reaction enthalpies with larger crown ethers than 18-crown-6 especially with dibenzo-30-crown-10 indicate that more than six donor atoms are taking part in the interaction with the complexed cation. The values of the reaction entropies of the largest crown ethers examined indicate the high sterical requirements of the complex formation. Obviously large crown ethers are able to encapsulate the complexed cation. The effectiveness of the encapsulation however depends upon the ring size and flexibility of the crown ethers.