Calorimetric titration study of the interaction of several uni- and bivalent cations with 15-crown-5, 18-crown-6, and two isomers of dicyclohexo-18-crown-6 in aqueous solution at 25.degree.C and .mu. = 0.1

Izatt, Reed M.; Terry, Richard E.; Haymore, Barry L.; Hansen, L. D.; Dalley, N. Kent; AVONDET, A. G.; Christensen, James J.

doi:10.1021/ja00440a028

Cited by 520 publications

(224 citation statements)

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“…In most cases 18-crown-6 derivatives exhibit some preference for S?+ over the other alkaline earth cations. This is in agreement with stability constant data for these carriers (accompanying paper) and crown ethers in general, which show optimal binding of the cation whose radius matches that of the macrocycle (22). As noted previously (16), binding selectivity does not directly result in transport selectivity of the same magnitude, although overall complex stability and selectivity both play a role in the transport process (23).…”

Section: Transport Selectivitiessupporting

confidence: 91%

Membrane transport systems. V. Coupled countertransport of alkaline earth cations and protons

Dulyea¹,

Fyles²,

Whitfield³

1984

Can. J. Chem.

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LYNN M. DULYEA, THOMAS M. FYLES, and DENNIS M. WHITFIELD. Can. J. Chem. 62, 498 (1984). The extraction and transport of alkaline earth cations from a basic to an acidic solution across an artificial membrane by crown ether carboxylic acids are reported. Monocarboxylate carriers achieve the transport via 2: 1 complexes or by ternary complexes in the presence of readily extractible anions, while dicarboxylate carriers transport cations as I : I complexes. Both types of carrier exhibit two regimes of kinetic behaviour depending on the relative concentrations of the carrier and the metal ion: a zero order regime in which the rate depends only on the carrier concentration, and a reversible consecutive first order regime in which the rate depends only on the metal ion concentration. In the former, the rate of adsorption of the carrier on the interface is presumed to be rate limiting while in the latter, the diffusion of metal ion to the interface is rate limiting. Carrier structure exerts a general influence over both the rate and selectivity of transport but this influence varies with the kinetic regime considered.LYNN M. DULYEA, THOMAS M. FYLES et DENNIS M: WHITFIELD. Can. J . Chem. 62, 498 (1984). On rapporte des extractions et des transports de cations d'alcalino-terreux de solutions basiques vers des solutions acides a travers une membrane artificielle effectuts par des Cthers couronnes d'acides carboxyliques. Les transporteurs monocarboxylCs permettent d'effectuer les transferts via des complexes 2: 1 ou par le biais de complexes ternaires en presence d'anions qui peuvent &tre extraits facilement; par ailleurs, les transporteurs dicarboxylts effectuent le transport des cations sous forme de complexes I : I . Les deux types de transporteurs presentent deux rtgimes de comportement cinCtique diffkrents suivant les concentrations relatives de transporteur et d'ion mCtallique: un rCgimc d'ordre zCro dans lequel la vitesse dtpend uniquement de la concentration de transporteur et un regime du premier ordre constcutif et rCversible dans lequel la vitesse dCpend uniquement de la concentration de l'ion mttallique. Dans le premier rCgime, on suppose que la vitesse d'adsorption du transporteur a I'interfacc est I'Ctape dkterminante alors que dans le dernier regime, la diffusion de l'ion mCtallique a I'interface serait I'ttape dtterminante. La structure du transporteur exerce une influence gCntrale i la fois sur la vitesse et sur la sClectivit6 du transport mais cette influence varie avec le regime cinCtique considtrC.[Traduit par le journal]

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Section: Transport Selectivitiessupporting

confidence: 91%

Membrane transport systems. V. Coupled countertransport of alkaline earth cations and protons

Dulyea¹,

Fyles²,

Whitfield³

1984

Can. J. Chem.

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“…14 (1), (7), (10), (11), (12), and (17) by the successive-approximation method. The log K ex and log K MLA values are listed in Tables 2 and 6, respectively.…”

Section: Theory and Resultsmentioning

confidence: 99%

Solvent Extraction of Alkali Metal (Li - Cs) Picrates with 18-Crown-6 into Various Diluents. Elucidation of Fundamental Equilibria which Govern the Extraction-Ability and -Selectivity

et al. 1998

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In order to elucidate the extraction-ability and -selectivity of a crown ether for metal ions from the standpoint of equilibrium, it is necessary to analyze the overall extraction equilibrium of a metal salt with the crown ether by the fundamental equilibria. It can be considered that the overall extraction equilibrium of a monovalent metal salt (MA) with an electroneutral crown ether (L) into an organic solvent of low dielectric constant consists of four underlying equilibria. Among these basic equilibrium constants, it is next to impossible to determine the ion-pair formation constant in water and the distribution constant of the MLA 1:1:1 complex, because both the ML + and MLA complexes are not stable in water. It has been reported that the ion-pair formation constant in water of a crown ethermonovalent metal ion complex with an anion can be determined by solvent extraction.1,2 Even the ion-pair formation constant in water of a highly lipophilic crown ether-monovalent metal ion complex with an anion can be determined by this method.3 The distribution constant of the MLA complex is calculated from the other three fundamental equilibrium constants and the overall extraction equilibrium constant. By considering the concentrations in the aqueous phase of MLA and MA as well as those of M + and ML + , the actual constants of the overall extraction equilibrium, the aqueous ion-pair formation, and the distribution of the MLA complex are obtained by a successive approximation method. 4 The ion-pair formation constant and the distribution constant provide information about the structure in water and the behavior in organic solvents of the MLA complex, respectively.In this study, actual constants of the overall extraction equilibrium, the distribution for various diluents of low dielectric constant, and the aqueous ion-pair formation of 18-crown-6 (18C6)-alkali metal picrate 1:1:1 complexes were determined at 25˚C to clarify the highest extraction-ability and -selectivity of 18C6 for K + . ExperimentalMaterials 18-Crown-6 (Nisso Co., Ltd.) was recrystallized from acetonitrile and, prior to use, dried at 80˚C in a vacuum. The purity was checked by the melting point (39.2 -40.0˚C). Picric acid, LiOH·H 2 O, NaOH, and KOH were analytical-grade reagents. Rubidium and caesium hydroxides were of reagent grade. The concentrations of solutions of all the alkali metal hydroxides and picric acid were determined by neutralization titration. All of the organic solvents were analyticalgrade reagents. Although 1,2-dichloroethane was purified by distillation, the others were not purified. They were washed several times with distilled water prior to use. 215 ANALYTICAL SCIENCES FEBRUARY 1998, VOL. 14 1998 © The Japan Society for Analytical Chemistry † To whom correspondence should be addressed. The actual constants of the overall extraction equilibrium, the distribution for various organic solvents having low dielectric constants, and the aqueous ion-pair formation (KMLA) of 18-crown-6 (18C6)-alkali metal (Li -Cs) picrate 1:1:1 complexe...

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“…Izatt et al (1976) report the binding constant of sodium ions to 18-crown-6 to be 6.3 M" with an enthalpy change of -2,250 cal mol" at 25 " C , to form a 1:l complex. With sodium ions at a concentration of 0.20 M, in large excess, the degree of saturation of the ether would thus be 0.20 K B / ( l + 0.20 K B ) = 0.56.…”

Section: Calorimetric Enthalpiesmentioning

confidence: 99%

“…Even in these cases involving relatively simple molecules, there were significant differences between van't Hoff and calorimetric enthalpies. Izatt et al (1976) and Briggner and Wadso (1991) published calorimetric data on the binding of barium chloride to 18-crown-6 ether, the latter publication including equilibrium data at three temperatures. This system would appear to be an excellent system for further study of the problem concerning van't Hoff and calorimetric enthalpies because of its simplicity:…”

mentioning

confidence: 99%

Significant discrepancies between van't hoff and calorimetric enthalpies. II

1995

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Isothermal calorimetric titration of 18-crown-6 ether with BaClz in pure aqueous solution over the temperature range 7-40 "C gives precise binding constants and enthalpy changes. Nonlinear least-squares fitting of the binding constants to the integrated van't Hoff equation, including a temperature-independent change in heat capacity, leads to van't Hoff enthalpies that differ significantly from the observed calorimetric enthalpies. This perplexing discrepancy appears at present to be very widely occurring. Keywords: calorimetric enthalpies; calorimetry; temperature variation of equilibrium constants; van't Hoff enthalpiesIn a recent paper (Naghibi et al., 1995), we pointed out the frequent occurrence of discrepancies between van't Hoff enthalpies derived from the temperature variation of equilibrium constants and enthalpies determined by direct calorimetric measurements. To date we have not found a single case where there is agreement, to within experimental uncertainty, between these two types of enthalpy values. All the systems but two considered in our earlier paper involved proteins, the two exceptions being the binding of cyclohexanol to a-and 0-cyclodextrins. Even in these cases involving relatively simple molecules, there were significant differences between van't Hoff and calorimetric enthalpies. Izatt et al. (1976) and Briggner and Wadso (1991) published calorimetric data on the binding of barium chloride to 18-crown-6 ether, the latter publication including equilibrium data at three temperatures. This system would appear to be an excellent system for further study of the problem concerning van't Hoff and calorimetric enthalpies because of its simplicity:18-crown-6 is a solid cyclic polyether of 264 Da molecular mass; both reactants are readily available in very pure form; and they can be weighed and dissolved in pure water for the reaction. Izatt et al. reported data at 25 "C only, and Briggner and Wadso limited their study to three temperatures. Because our method for analyzing such data requires measurements at four or more temperatures, we have undertaken further study of this system.

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Calorimetric titration study of the interaction of several uni- and bivalent cations with 15-crown-5, 18-crown-6, and two isomers of dicyclohexo-18-crown-6 in aqueous solution at 25.degree.C and .mu. = 0.1

Cited by 520 publications

References 0 publications

Membrane transport systems. V. Coupled countertransport of alkaline earth cations and protons

Membrane transport systems. V. Coupled countertransport of alkaline earth cations and protons

Solvent Extraction of Alkali Metal (Li - Cs) Picrates with 18-Crown-6 into Various Diluents. Elucidation of Fundamental Equilibria which Govern the Extraction-Ability and -Selectivity

Significant discrepancies between van't hoff and calorimetric enthalpies. II

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