勝田 正一

Equilibrium constants (K-MLA(0)/mol(-1) dm(3)) for the ion-pair formation of a complex ion NaL+ with ReO4- in water were determined potentiometrically at 25 degrees C and the ionic strength (I) of 0 mol dm(-3) using a Na+-selective electrode. Here, crown ethers, L, were 15-crown-5 ether (15C5), benzo-15C5, 18-crown-6 ether (18C6) and benzo-18C6. Also, NaReO4 was extracted by the L into 1,2-dichloroethane and then extraction constants (K-ex/mol(-2) dm(6)) for the species, NaLReO4, were determined at 25 degrees C by AAS. These K-ex values were resolved into four component equilibrium constants containing K-MLA calculated at given I values. Based on these data, extraction-abilities of the L against the perrhenate were discussed in comparison with those of sodium picrate-L systems reported previously. (c) 2006 Elsevier B.V. All rights reserved.

The constants of overall extraction equilibrium (K-ex) and partition (K-D,K-MLA) for various diluents and aqueous ion-pair formation (K-MLA) of alkali metal (Li-Cs) picrate (MA) 1:1:1 complexes (MLA) with benzo-18-crown-6 (B18C6) and its open-ring analogue 1,2-bis[2-(2-methoxyethoxy)ethoxy]benzene (AC-B18C6) were determined at 25 degrees C, L being B18C6 or AC.B18C6; the distribution constants of AC.B18C6 were measured at 25 degrees C. The partition behavior of AC.B18C6 and the MLA complexes closely obeys regular solution theory, omitting chloroform; the molar volumes and the solubility parameters of AC-B18C6 and the MLA complexes were determined. The extraction selectivities of AC.B18C6 and B18C6 for the alkali metal picrates increase in the order Li<Na<Cs<K or Rb< or approximate to Rb or K and Li<<Na<Cs<Rb<K, respectively, The extraction selectivity of B18C6 for neighboring alkali metal ions in the periodic table is superior to that of AC-B18C6. The macrocyclic effect on the extraction-ability and -selectivity was quantitatively elucidated by the four fundamental equilibrium constants. (C) 2006 Elsevier B.V. All rights reserved.

Ion-pair formation constants (K-MLX in mol(-1) (.) dm(3)) for M(B18C6)(+), M(15C5)(+), or M(B15C5)(+) with pairing anions (X-) in water were determined by potentiometry with ion-selective electrodes at 25 degrees C over wide ranges of the ionic strength (I). The symbols B18C6, 15C5, and B15C5 denote benzo-18-crown-6 ether, 15-crown-5 ether, and benzo-15C5, respectively; metal salts, MX, used are sodium picrate (NaPic), KPic, NaBPh4, NaMnO4, and KMnO4. The K-MLX values at I = 0 mol dm(-3) (K(MLX)degrees) were evaluated from analyzing the I dependence of the log K-MLX values determined. Then, effects of shapes of X-, the benzo group of the ethers, their ring sizes, and the shielding of the metal ions, M+, by the ethers on these K(MLX)degrees values were discussed in comparison with the values previously reported on M(18C6)X, M(15C5)Pic, and M(Bl5C5)Pic. Also, center-to-center distances in the M(18C6 derivatives)(+)-X- or M(15C5 ones)(+)-X- pairs were estimated from Bjerrum's equation.

Ion-pair formation constants (K degrees(MLA)) for crown ether-complex ions (ML+) with picrate ion (Pic(-)) in water (w) at the ionic strength (I) = 0 mol dm(-3) and 25 degrees C were determined by potentiometry with ion-selective electrodes for MPic-15-crown-5 ether (15C5), -benzo- 15C5 (B15C5) (M = Na, K) and LiPic-18-crown-6 ether (18C6) systems. Also, the same kind of constant for Li+ with Pic(-) was determined potentiometrically. The K-MLA values estimated at given I were compared with those given previously by solvent extraction with its data analysis by the regular solution theory. Consequently, a large difference between these K-MLA values was observed for the 15C5 systems; similar differences had been obtained for NaPic- and YPic-18C6 ones. The cause for these differences was discussed based on the Scatchard-Hildebrand equation and then the differences were corrected by referring to the potentiometric K-MLA. In the correction, extraction constants for the above systems into more than ten organic (o) solvents were recalculated together with distribution constants for the ion-pair complexes ML(+)Pic(-) between the w- and o-phases. (c) 2005 Elsevier B.V. All rights reserved.

Formation constants (K-ML) for 1:1 complexes of 1,2-bis[2-(2-methoxyethoxy)ethoxy]benzene (AC.B18C6), a linear counterpart of benzo-18-crown-6 (B18C6), and B18C6 with various mono- and divalent cations were determined in water at 25 degrees C by conductometry; the K-ML value for the B18C6-Li+ complex was also determined in acetonitrile. By using the K-ML and literature values, transfer activity coefficients of the AC.B18C6- and B18C6-alkali metal ion complexes from water to polar nonaqueous solvents were calculated. The selectivity order in water of AC.B18C6 for univalent cations is different from that of B18C6, but for bivalent cations they are almost the same. For the same cation, the aqueous log K-ML value is lower for AC.B18C6 than for B18C6 except for size-misfitting smaller cations (H+, Li+, Cd2+). In general, cyclization of the two binding-arms of AC.B18C6 increases the selectivity and stability for the cations in water. Although AC.B18C6 is always less hydrophilic than B18C6, the AC.B18C6-alkali metal ion complex is more hydrophilic than the corresponding B18C6 complex. It follows that the alkali metal ion in the AC.B18C6 complex is less effectively shielded and dehydration of AC.B18C6 upon complexation in water is less efficient, compared with B18C6. Hydrogen bonding between AC.B18C6 or B18C6 and water causes the unexpectedly lowest aqueous stability of the AC.B18C6- or B18C6-alkali metal ion complex among all the solvents. The same holds for the stabilities of the other metal ion complexes with AC.B18C6 or B18C6.

Ion-pair formation constants (mol(-1) dm(3) unit), K-MX for a univalent metal salt (MX) and K-MLX for its ion-pair complex (ML+X-) with a crown ether (L) in water, were determined at various ionic strengths (I) and 25degreesC by potentiometry with ion-selective electrodes for MX = NaPic, NaMnO4, NaBPh4, KPic, and KMnO4; and MLX = Na(18C6)Pic, K(18C6)Pic, and Na(18C6) BPh4, where Pic(-) and 18C6 denote a picrate ion and 18-crown-6 ether, respectively. Equations for analyzing I-dependence of log K-MLX and log K-MX were derived and fitted well to the I-dependence using a non-linear regression analysis. The equilibrium constants at I = 0 mol dm(-3), K(MLX)degrees and K(MX)degrees, were simultaneously obtained from the analysis. The experimental values of KMLX and KMX were only in agreement with the values calculated from K(MLX)degrees and K(MX)degrees, respectively, in the ranges of higher I.

The constants for overall extraction into various diluents of low dielectric constants (Kex) and aqueous ion-pair formation (K MLA) of dibenzo-18-crown-6 (DB18C6)-sodium and potassium perchlorate 1:1:1 complexes (MLA) were determined at 25°C. The Kex value was analyzed by the four underlying equilibrium constants. The KMLA values were determined by applying our established method to this DB18C6/alkali metal perchlorate extraction system. The KM(DB16C6)A value of the perchlorate is much greater for K+ than for Na+, and is much smaller than that of the picrate. The KMLA value makes a negative contribution to the extractability of DB18C6 for MClO4, whereas the value of the MLA distribution-constant does a major one. The partition behavior of M(DB18C6)ClO4 obeys the regular solution theory. However, the M(DB18C6)ClO4 complexes in the diluent of high dipole moment somewhat undergo the dipole-dipole interaction. DB18C6 always shows high extraction selectivity for KClO4 over NaClO4, which is governed largely by the much greater KMLA value for K + than for Na+. The K+ extraction-selectivity of DB18C6 over Na+ for perchlorate ions is comparable to that for picrate ions. By comparing this perchlorate system with the picrate one, the anion effects on the extraction-efficiency and -selectivity of DB18C6 for Na+ and K+ was discussed in terms of the fundamental equilibrium constants.

The constants for overall extraction into various diluents of low dielectric constants (K-ex) and aqueous ion-pair formation (K-MLA) of dibenzo-18-crown-6 (DB18C6)-sodium and potassium perchlorate 1:1:1 complexes (MLA) were determined at 25degreesC. The Kex value was analyzed by the four underlying equilibrium constants. The KMLA values were determined by applying our established method to this DB18C6/alkali metal perchlorate extraction system. The K-M(DB18C6)A value of the perchlorate is much greater for K+ than for Na+, and is much smaller than that of the picrate. The KMLA value makes a negative contribution to the extractability of DB18C6 for MClO4, whereas the value of the MLA distribution-constant does a major one. The partition behavior of M(DB18C6)ClO4 obeys the regular solution theory. However, the M(DB18C6)ClO4 complexes in the diluent of high dipole moment somewhat undergo the dipole-dipole interaction. DB18C6 always shows high extraction selectivity for KClO4 over NaClO4, which is governed largely by the much greater KMLA value for K+ than for Na+. The K+ extractionselectivity of DB18C6 over Na+ for perchlorate ions is comparable to that for picrate ions. By comparing this perchlorate system with the picrate one, the anion effects on the extraction-efficiency and -selectivity of DB18C6 for Na+ and K+ was discussed in terms of the fundamental equilibrium constants.

The constants of overall extraction equilibrium (K-ex) and distribution (K-D,K-MLA) for various diluents and aqueous ion-pair formation (K-MLA) of dibenzo-24-crown-8 (DB24C8)-alkali metal (Na-Cs) picrate (MA) 1:1:1 complexes (M(DB24C8)A) were determined at 25 degreesC; the partition constants of DB24C8 were also measured at 25 degreesC. The distribution behavior of DB24C8 and M(DB24C8)A complexes can be explained by regular solution theory; the molar volumes and the solubility parameters of DB24C8 and M(DB24C8)A were determined. The log K-D,K-MLA value for the same diluent decreases from Na to K and increases from K to Cs; however, the reverse is true of the log K-MLA values. The extraction selectivity of DB24C8 for the alkali metal picrates decreases in the order Cs>Rb>K>Na or Cs>K greater than or equal to or >Rb>Na. This is governed largely by the aqueous stability order for the M(DB24C8)(+) complex ions. For every diluent, the plot of log K-ex values against the reciprocal effective ionic radii of the alkali metals gives a straight line, which is related to Bom's formula of solvation free energy. The reason for this was elucidated. (C) 2004 Elsevier B.V. All rights reserved.

Ion-pair formation constant (K-Agpic in mol(-1) dm(3)) of silver picrate (AgPic), those (K-AgLPic) of its ion-pair complexes (AgLPic) with crown ethers (L) and complex formation constants (K-AgL) of Ag+ with L(15-crown-5 ether (15C5) and benzo- 15C5) in water (w) were determined potentiometrically at 25 degreesC. Compounds used as L were 48-crown-6 ether (18C6), its benzo-derivative (B 18C6) and the two 15C5 derivatives. Extraction constants (K-ex in mol(-1) dm(3)) of AgPic with L (15C5, 18C6, B18C6) from acidic w-phases into either C6H6 or CHCl3 were recalculated from K-AgPic, K-AgL, K-AgLPic and data opened in previous papers. Thus obtained K-ex was divided into five component equilibrium constants containing K-AgL and K-AgLpic anew. Then, contributions of the component constants, K-AgL, K-AgLpic and distribution constants of AgLPic between the w- and C6H6-phases, to K-ex were discussed and compared with corresponding extraction systems of NaPic and KPic with 18C6. (C) 2003 Elsevier B.V. All rights reserved.

The thermodynamic parameters for transfer of 15-crown-5 (15C5) and benzo-15-crown-5 (B15C5) between polar solvents (s) were precisely determined by solvent extraction. By using these data and the related literature values, the enthalpy (DeltaH(tr)(o)) and entropy changes (DeltaS(tr)(o)) of transfer of the 1:1 complexes of 15C5 and B15C5 with alkali metal ions (M+) between the polar solvents were calculated from the Ph4As+/ Ph4B- assumption via a thermodynamic cycle. Both the DeltaH(tr)(o) and DeltaS(tr)(o) values from water to s for 15C5 and B15C5 are all positive, reflecting hydrogen bonding between water and the ether oxygen atoms. The DeltaH(tr)(o)(H2O --> s) value is always greater for 15C5 than for B15C5. This is attributed to the stronger interaction with water of the aliphatic ether oxygen atom compared with the aromatic one. The enthalpic interaction with the solvents of the crown-5 complex is governed largely by that of the W ion. The M(15C5)(+) and M(B15C5)(+) complexes act as hydrophobic structure-makers in water. Generally, the complexation in the solvent of 15C5 with Na+ is enthalpically less favorable than that with K+ {DeltaH(Na(15C5))(o)(s) > DeltaH(K(15C5))(o)(s)}. This is caused mostly by the much smaller DeltaH(tr)(o)(Na+: gas --> s) value compared with K+. However, the larger DeltaH(tr)(o)(Na(15C5)(+): gas --> s) value compared with K+ also contributes to the fact that DeltaH(Na(15C5))(o)(S) > DeltaH(K(15C5))(o)(s). (C) 2003 Elsevier B.V. All rights reserved.

Ion-pair formation constants (K-MLA mol(-1) dm(3)) of Na+- and K+-18-crown-6 ether (18C6) complexes with MnO4- in water (w) were determined potentiometrically at 25 degreesC. Simultaneously, extraction constants (K-ex mol(-2) dm(6)) of the permanganates with 18C6 from w into 1,2-dichloroethane at 25 degreesC were obtained from the spectrophotometric determination of distribution ratios of the permanganates. These K-ex values were divided into K-MLA and other three component equilibrium constants and thereby extraction-selectivity and -ability were discussed in comparison with corresponding metal picrate-18C6 extraction systems reported before. (C) 2003 Elsevier Science B.V. All rights reserved.

Stability constants (KML) of 1: 1 benzo-15-crown-5 (B15C5) complexes with alkali metal ions were conductometrically measured in water at 25 C. Transfer activity coefficients of B15C5 and 15-crown-5 (15C5) from water to polar nonaqueous solvents were determined at 25degreesC. By using these data and the literature values, transfer activity coefficients of the B15C5 and 15C5 complexes with alkali metal ions from water to the polar nonaqueous solvents were calculated to study the solute-solvent interaction of the crown ether complexes. The stability of the B15C5 complex is lower in water than in any other nonaqueous solvent. The K-ML value for B15C5 is always smaller than the corresponding K-ML value for 15C5. The interaction of the B15C5 or the 15C5 complex with the solvents depends on the alkali metal ion in the crown cavity. All the B15C5 and 15C5 complexes undergo hydrophobic hydration, which is particularly stronger for the B15C5 complexes with Na+ and K+. The unexpectedly lowest stability of the B15C5- or the 15C5-alkali metal ion complex in water among all the solvents is caused by the hydrogen bonding between ether oxygen atoms of uncomplexed B15C5 or 15C5 and water.

To quantitatively elucidate the effects of the benzo group on the extraction-selectively and -ability of benzo-15-crown-5 (B15C5) for alkali metal ions, the constants of the overall extraction (K-ex), the distribution for various diluents having low dielectric constants (K-D,K-MLA), and the aqueous ion-pair formation (MLA) of B15C5-alkali metal (Li, Na, K) picrate 1: 1: 1 complexes (MLA) were determined at 25 degreesC. The partition constants of B15C5 were also measured at 25 degreesC. The log K-MLA values for Li+, Na+, and K+ are 0.32 +/- 0.22, 2.66 +/- 0.19, and 0.71 +/- 0.47, respectively. In going from 15-crown-5 (15C5) to B15C5, the benzo group considerably decreases the K-MLA value for the same alkali metal ion. The distribution behavior of B15C5 and its 1:1:1 complexes with the alkali metal picrates closely obeys regular solution theory, omitting chloroform. Molar volumes and solubility parameters of B15C5 and the 1:1:1 complexes were determined. For every diluent, the K-ex value for B15C5 increases in the order Li+ < K+ < Na+. K-D,K-MLA makes an unfavorable contribution to the Na+ extraction-selectivity of B15C5 because of the smallest molar volume of the Na(B15C5)A complex. The Na+ extraction-selectivity of B15C5 is determined completely by much the highest K-Na (B15C5)A value. The extraction-ability and -selectivity of B15C5 for the alkali metal picrates are compared with those of 15C5 on the basis of the underlying equilibrium constants.

To investigate quantitatively the anion effect on the extraction-ability and -selectivity of benzo-18-crown-6 (B18C6) for alkali metal ions, the constants for overall extraction into various diluents having low dielectric constants (K-ex) and aqueous ion-pair formation (K-MLA) of B18C6-sodium and potassium perchlorate 1: 1: 1 complexes (MLA) were determined at 25 degreesC. The K-ex value was analyzed by the four fundamental equilibrium constants. The K-MLA values were determined by applying our established method to this perchlorate extraction system. The K-M(B18C6)A value of the perchlorate is much larger for K+ than for Na+, and is much smaller than that of the picrate. The K-M(B18C6)A value makes a minor contribution to the magnitude of K-ex for the perchlorate system, but a major contribution to that for the picrate one. The distribution behavior of the B18C6 1:1:1 complexes with the alkali metal perchlorates follows the regular solution theory. For the diluent with a high dipole moment, however, the 1:1:1 complexes somewhat undergo the dipole-dipole interaction. B18C6 always shows very high extraction selectivity for KClO4 over NaClO4, which is determined mostly by the much greater log/(log K-MLA) value for K+ than for Na+. The extraction-ability and -selectivity of B18C6 for Na+ and K+ ions with a perchlorate ion were compared with those with a picrate ion in terms of the fundamental equilibrium constants. The K+ extraction-selectivity of B18C6 over Na+ for the perchlorate system is superior to that for the picrate one. which is caused largely by the greater log/(log K-K(B18C6)A) - log/(log K-Na(B18C6)A) value for the perchlorate than for the picrate. The perchlorate system is recommended for extraction separation of K+ from Na+. (C) 2002 Elsevier Science B.V. All rights reserved.

A theoretical equation of the reversible current -potential curves is derived for the competitive ion-transfer of two kinds of cations present in an aqueous (w) phase simultaneously facilitated by a macrocyclic ligand (L) present in an organic (o) phase. Especially, for the two limiting cases, i.e. case (A): c(M)*(i) (j = 1, 2) much greater than c(L)* and case (B): c(L)* much greater than c(M)*, (where c(M)*(j) and c(L)* denote the bulk concentrations of cation Mi in the w-phase and of L in the o-phase, respectively), simple explicit expressions are derived and a method analyzing the facilitated waves is presented. Furthermore, the main part of the theoretical predictions obtained is verified experimentally at 25 degreesC by using the ion-transfer-polarographic method with the electrolyte dropping electrode, for the following four combinations: (i) competitive cations: protonated alanine and H+. L: benzo-18-crown-6 ether; (ii) Na+ and Li+, benzo-15-crown-5 ethers (iii) K+ and Na+, dibenzo-18-crown-6 ether, and (iv) Na+ and Ba2+, dibenzo-24-crown-8 ether. (C) 2001 Elsevier Science BN. All rights reserved.

To quantitatively elucidate the effects of the side chains and diluents on the extraction selectivity for sodium and potassium picrates of 15-(2,5-dioxahexyl)- 15-methyl-16-crown-5 (L16C5) from the viewpoint of equilibrium, the constants for the overall extraction (K-ex). the partition for various diluents of low dielectric constants: (K-D.MLA), and the aqueous ion-pair formation (K-MLA) of L16C5-sodium and -potassium picrate 1:1:1 complexes were determined at 25 degreesC; the distribution constants of L16C5 were also measured at 25 degreesC. The log K-MLA values for Na+ and K+ are 2.74 +/- 0.29 and 1.70 +/- 0.36, respectively. In going from 16-crown-5 (16C5) to L16C5. the side chains decrease the K-MLA value, but do not increase the difference in K-MLA between Na+ and KC. The distribution behavior of L16C5 and its 1:1:1 complexes with the alkali metal picrates closely obeys regular solution theory, except for chloroform. Molar volumes and solubility parameters of L16C5 and the 1:1:1 complexes were determined. The magnitude of K-ex is mainly governed by the K-M(L16C5)A value. For every diluent, L16C5 shows Na (+) extraction selectivity over K+. The Naf extraction selectivity of L16C5 is determined completely by K-M(L16C5)A. The extraction ability and selectivity for sodium and potassium picrates by L16C5 are compared with those of 16C5 on the basis of the fundamental equilibrium constants. (C) 2001 Elsevier Science B.V. All rights reserved.

The Gibbs free energy (Delta G degrees(tr)), enthalpy (Delta H degrees(tr)), and entropy changes (Delta S degrees(tr)) for transfer of 18-crown-6 (18C6) from water to various polar nonaqueous solvents were precisely determined by solvent extraction. By using these data, and the known values of thermodynamic quantities for transfer of alkali metal ions (M+) and those for complexation in water and the nonaqueous solvents, we calculated the thermodynamic parameters of transfer of the M(18C6)(+) complexes from water to the solvents from the Ph4As+/Ph4B- assumption via a thermodynamic cycle. The Delta H degrees(tr) and Delta S degrees(tr) values of the M(18C6)(+) complexes vary considerably with the solvent and with the alkali metal ion, and also those of 18C6 do with the solvent. The values of Delta H degrees(tr) and Delta S degrees(tr) are all positive and large, reflecting strong hydrogen bonding between 18C6 and water. 18C6 complexes with Rb+ and Cs+ are enthalpically more stable in a given solvent than those with Na+ and K+. This shows that Na+ and K+ in the complexes are more effectively shielded by 18C6 from surrounding solvents than Rb+ and Cs+. Among all the M(18C6)(+) complexes, positive Delta H degrees(tr) value from water to DMF is found only for Na(18C6)(+). It is concluded from this and the other results that the Na(18C6)(+) complex undergoes hydrophobic hydration more strongly than the other complexes do.

Formation constants of 1 : 1 19-crown-6 (19C6) complexes with alkali metal ions were determined conductometrically at 25 degrees C in acetonitrile (AN), propylene carbonate (PC), methanol, DMF, and DMSO. 19C6 always forms the most stable complex with K+. The selectivity order of 19C6 for heavy alkali metal ions is K+ > Rb+ > Cs+. The selectivity for Na+ varies with the solvent; that for Li+ is the second lowest (AN, DMSO) or the lowest (PC). Transfer activity coefficients ((S)gamma(H2O)) of 19C6 from water to the nonaqueous solvents (S) were measured at 25 degrees C. The contributions of a methylene group and an ether oxygen atom to the log (S)gamma(H2O) value of a crown ether were obtained. The (S)gamma(H2O) values of the 19C6-alkali metal ion complexes ((S)gamma(H2O) (ML+)) were calculated, M+ and L denoting an alkali metal ion and a crown ether, respectively. For AN, PC, and CH3OH, although the M+ ion is more strongly solvated by water than by AN, PC, or CH3OH, the log (S)gamma(H2O) (ML+) is larger than the corresponding log (S)gamma(H2O) (L) expect for the case of M+ = Li+. The higher lipophilicity of the 19C6 complex ion is attributed to an enforcement of the hydrogen-bonded structure of water for the complex ion caused by the greatly decreased hydrogen bonding between ether oxygen atoms and water upon complexation. For DMF and DMSO, the log (S)gamma(H2O) (ML+) is also greater than the corresponding log (S)gamma(H2O) (L). It was concluded from this finding that the unexpectedly lowest stability of the 19C6 complex ion in water is due to the hydrogen bonding between 19C6 and water. The stabilities and the log (S)gamma(H2O) of 19C6-alkali metal ion complexes were compared with those of 18C6 complexes.

The constants of the overall extraction equilibrium (K-ex), the partition for various diluents having low dielectric constants (K-D,K-MLA), the aqueous ion-pair formation (K-MLA), and the dimer formation in CCl4 of 16-crown-5 (16C5)-alkali metal (Na, K) picrate 1:1:1 complexes were determined at 25 degrees C; the distribution constants of 16C5 were also measured at 25 degrees C. The log K-MLA of Na and K are 4.14 +/- 0.19 and 3.05 +/- 0.28, respectively. The partition behavior of 16C5 and its 1:1:1 complexes with the alkalimetal picrates can be explained by regular solution theory, except for CHCl3; the molar volumes and solubility parameters of 16C5 and the 1:1:1 complexes were determined. The magnitude of K-ex largely depends on that of K-MLA. For every diluent, 16C5 always shows Na+ extraction-selectivity over K+. The K-MLA value most contributes to the extraction selectivity of 16C5 for Na+ over for K+ among the three fundamental equilibrium constants, the aqueous 1:1 complex-formation constant of 16C5 with the alkali metal ion, K-MLA, and K-D,K-MLA. Furthermore, correct contributions of a methylene group to distribution constants of organic compounds between diluents of low dielectric constants and water were determined by the distribution constants of 16C5 and 15-crown-5; the additivity of the contributions of functional groups to the partition constant of a crown ether was verified. (C) 1999 Elsevier Science B.V. All rights reserved.

Formation constants (K-ML) of 1 : 1 19-crown-6 (19C6) complexes with mono- (M+) and bivalent metal ions M2+ were determined in water at 25 OC by conductomecry. The KML value of 19C6 for M+ and M2+ decreases in the order Rbf 1 Kf > T1(+) > Na+ = Ag+ > Li+ approximate to Csf and Pb2+ > Ba2+ > Sr2+, Cd2+, Ca2+, respectively. The selectivity for the neighboring alkali metal ions in the periodic table is lower for 19C6 than for 18-crown-6 (18C6) except for the case of Rb+ and Cs+. The same is true for the alkaline earth metal ions. Generally, the KML values of 19C6 with M2+ are greater than those with M+. For Na+ and the ions which are smaller in size than Na+ Li+, Ca2+, Cd2+, the KML value is larger for 19C6 than for 18C6, but the contrary holds for all the other ions of larger sizes than Naf. The Limiting ionic molar conductivity (lambda(o)) of the 19C6-K+ complex in water at 25 OC was determined to be 43. Although 19C6 is larger than 18C6, the 19C6-K+ complex is much more mobile in water than the 18C6-K+ complex.

Extractions of alkali metal (Na-Cs) picrates (MA) with 15-crown-5 (15C5) into various diluents of low dielectric constant were conducted at 25 degrees C. Using the extraction data, the ion-pair formation constants (K-MLA) in water of 15C5-MA 1:1:1 complexes were determined by an equation derived from the regular solution theory (log K-MLA = 4.43 +/- 0.27 for Na, 3.27 +/- 0.42 for K, 3.58 +/- 0.35 for Rb, and 2.78 +/- 0.41 for Cs). The actual overall extraction equilibrium constants were obtained by considering the concentrations of the 1:1:1 15C5 complexes and the ion-pair formation between uncomplexed alkali metal and picrate ions in the aqueous phase. The distribution constants of the 15C5 complexes were calculated and their partition behavior is explained by the regular solution theory. Molar volumes and solubility parameters of 15C5 itself and the complexes were determined. Extraction-efficiency and -selectivity of 15C5 for alkali metal picrates were completely elucidated from the standpoint of equilibrium. (C) 1998 Elsevier Science B.V. All rights reserved.

The actual constants of the overall extraction equilibrium, the distribution for various organic solvents having low dielectric constants, and the aqueous ion-pair formation (K-MLA) Of 18-crown-6 (18C6)-alkali metal (Li-Cs) picrate 1:1:1 complexes were determined at 25 degrees C; the partition constants of 18C6 were also measured at 25 degrees C. The log K-MLA values are 2.53+/-0.21 for Li, 3.29+/-0.23 for Na, 4.76+/-0.27 for K, 4.62+/-0.36 for Rb, and 4.49+/-0.36 fur Cs. The relatively large difference in the log K-MLA value between light (Li, Na) and heavy alkali metals (K, Rb, Cs) reflects the difference in the structure of the 18C6-alkali metal ion 1:1 complex between light and heavy alkali metals. Almost all of the partition behavior of 18C6 and its 1:1:1 complexes with alkali metal picrates can be explained by regular solution theory. The molar volumes and solubility parameters of 18C6 and the complexes were determined. For every diluent, the extraction-selectivity order of 18C6 is K > Rb > Cs > Na > Li. The extraction-ability and -selectivity of 18C6 for the alkali metal ion were completely elucidated in terms of the four fundamental equilibria.