Extraction of sodium and potassium picrates with 16-crown-5 into various diluents. Elucidation of fundamental equilibria determining the extraction selectivity for Na(+) over K(+)

The constants of the overall extraction equilibrium (K(ex)), the partition for various diluents having low dielectric constants (K(D,MLA)), the aqueous ion-pair formation (K(MLA)), and the dimer formation in CCl(4) 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 logK(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 CHCl(3); 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,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.     

Extraction of sodium and potassium perchlorates with benzo-18-crown-6 into various organic solvents. Quantitative elucidation of anion effects on the extraction-ability and -selectivity for Na(+) and K(+)

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 degrees C. 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 KClO(4) over NaClO(4), 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(+).     

Solvent effects on extraction of alkali metal picrates with 15-crown-5 into various organic solvents. Elucidation of fundamental equilibria which govern extraction-efficiency and -selectivity

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 (logK(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.     

The solvent extraction of alkali metal picrates with 4,13-N,N'-dibenzyl-4,13-diaza-18-crown-6

Extraction of alkali metal picrates with N,N'-dibenzyl-18-crown-6 was carried out, with dichloromethane as water-immiscible solvent, as a function [ligand]/[metal cation]. The extractability of metal picrates (Li(+), Na(+), K(+), Rb(+), Cs(+)) was evaluated as a function of [L]/[M(+)]. The extractability of complex cation-picrate ion pairs decreases in this sequence: Li(+)>Rb(+)>Cs(+)>K(+)>Na(+). The overall extraction equilibrium constants (K(ex)) for complexes of N,N'-dibenzyl-18-crown-6 with alkali metal picrates between dichloromethane and water have been determined at 25 degrees C. The values of the extraction constants (logK(ex)) were determined to be 10.05, 6.83, 7.12, 7.83, 6.73 for Li(+), Na(+), K(+), Rb(+) and Cs(+) compounds, respectively. DB186 shows almost 2-fold extractability against Li(+) compared to the other metal picrates, whereas it shows no obvious extractability difference amongst the other metal cations when [L]/[M(+)] is 0.2-1. However, an increasing extractability is observed for Cs(+) when [L]/[M(+)] [1].     

Extraction of Alkali Metal (Li, Na, K) Picrates with Benzo-15-crown-5 into Various Organic Solvents. Elucidation of Fundamental Equilibria Determining the Extraction-ability and -selectivity

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), thedistribution for various diluents having low dielectric constants (K_D,MLA), and the aqueousion-pair formation (K_MLA) of B15C5-alkali metal (Li, Na, K) picrate 1:1:1 complexes (MLA) weredetermined at 25 °C. The partition constants of B15C5were also measured at 25 °C. 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 decreasesthe K_MLA value for the same alkali metal ion. The distributionbehavior of B15C5 and its 1:1:1 complexes with the alkali metal picrates closely obeys regularsolution theory, omitting chloroform. Molar volumes and solubility parameters of B15C5and the 1:1:1 complexes were determined. For every diluent, the K_ex valuefor B15C5 increases in the order Li⁺ < K⁺ < Na⁺. K_D,MLA makes anunfavorable 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 15C5on the basis of the underlying equilibrium constants.     

Hydration effect on the ion-pair extraction of lithium picrate by hydrophobic benzo-15-crown-5 ether into various less-polar diluents.

The ion-pair formation constant (K(MLA)(0) in mol(-1) dm(3)) for Li(B15C5)(+) with a picrate ion (Pic(-)) in water was determined by potentiometry with a K(+)-selective electrode at 25 degrees C and an ionic strength of 0, where B15C5 denotes benzo-15-crown-5 ether. Using the concentration equilibrium constants, K(MLA), estimated from this value, the extraction constants (mol(-2) dm(6) unit) of about ten diluents were re-calculated from previously reported extraction data. Also, the distribution constants of an ion-pair complex, Li(B15C5)Pic, between water and the diluents were re-estimated. A disagreement in the determined K(MLA) value between a solvent-extraction method and potentiometry was explained in terms of the Scatchard-Hildebrand equation; it came from the fact that the hydration of Li(I) in Li(B15C5)Pic was larger than that of free B15C5 in water. Then, the previously determined value by the former method was re-estimated using the potentiometric K(MLA) value.     

Evaluation of the Hydrophilic Property of Sodium Ion-pair Complexes with 3m-Crown-m Ethers (m = 5, 6) and Their Benzo-derivatives by Solvent Extraction

The ion-pair formation constants {K(j)(0): j = MA (metal salt), MLA} of NaO(2)CCF(3) (Na(+)tfa(-)) and its ion-pair complexes (MLA) in water (w) were determined potentiometrically at 25 degrees C and an ionic strength (I) of zero. 15-Crown-5 (15C5), 18-crown-6 ethers (18C6), and their mono-benzo derivatives were used as crown ethers (L). The extraction of Natfa by these four L from w into 1,2-dichloroethane was done at 25 degrees C, and then the extraction constants (K(ex)) for NaLtfa were calculated by using the K(j) values, which were estimated from the corresponding K(j)(0) ones at I of the w-phases, and other equilibrium constants. Also, the distribution constants (K(D,MLA)) of NaLtfa between the two phases were obtained from a thermodynamic cycle expressing K(ex). An interaction of w-molecules with NaLA was considered using a relation of log K(D,MLA) with log K(D,L), derived from the Scatchard-Hildebrand equation, where K(D,L) denotes the distribution constant of L between the two phases. The interaction increased in the order of NaL (picrate) < free L 相似文献   

Photometric reagents for alkali metal ions, based on crown-ether complex formation--III. 4'-picrylaminobenzo-15-crown-5 derivatives

An extraction study of alkali metal cations has been made with crown-ether reagents, 4'-picrylaminobenzo-15-crown-5 derivatives (HL). On dissociation in alkaline medium, the orange HL gives the blood-red anion L(-) and extracts alkali metal ions into chloroform as coloured complexes of composition ML.HL or ML. The ease of extraction decreases in the order, K(+) > Rb(+) > Cs(+) > Na(+) > Li(+). The extracted complexes are ML.HL for K(+) and Rb(+), and both ML.HL and ML for Na(+). The Li(+) complex is not extracted. The photometric determination of 10-800 ppm of K(+) is possible in the presence of other alkali and alkaline earth metal ions.     

Substitution effect,absorption, and fluorescence behaviors of 11,12-benzo-1,7,10,13-tetraoxa-4-aza- cyclopentadec-11-ene (benzoaza-15-crown-5) derivatives upon cation complexation in solvent extraction

Substitution effect, absorption, and fluorescence behaviors of some benzoaza-15-crown-5 derivatives upon cation complexation in solvent extraction were studied. The introduction of a substituent on the nitrogen atom in benzoaza-15-crown-5 enhanced extractabilities in the solvent extraction of aqueous alkali metal picrates. The nondonating substituents raised the cation selectivity for Na(+) over K(+), but the donating substituents reduced the cation selectivity. The absorption and fluorescence spectral behavior was different with the alkali metal cations.     

Equilibrium studies on complexation in water and solvent extraction of zinc(II) and cadmium(II) with benzo-18-crown-6

The formation constants (K(ML)) in water of 1:1 complexes of benzo-18-crown-6 (B18C6) and 18-crown-6 (18C6) with Zn(2+) and Cd(2+), the sizes of which are much smaller than the ligand cavities, were determined at 25 degrees C by conductometry. Compared with Cd(2+), the crown ethers form more stable complexes with Zn(2+) although the size of Zn(2+) is less suited for the cavities. B18C6 forms a more stable complex with each metal ion than 18C6. Moreover, the extraction equilibria of these metal ions (M(2+)) with B18C6 (L) for the benzene/water system in the presence of picric acid (HA) were investigated at 25 degrees C. The association between L and HA in benzene was examined for evaluating the intrinsic extraction equilibria of M(2+) with B18C6. The extracted species were found to be MLA(2) and ML(2)A(2), and the overall extraction constants (K(ex,1) and K(ex,2), respectively) were obtained. The values of K(ex,1) for these metal ions are almost the same, but the K(ex,2) is larger for Zn(2+) than for Cd(2+). The extraction selectivity was interpreted quantitatively by the constituent equilibrium constants, i.e. K(ML), the ion-pair extraction constant of ML(2+) with A(-), and the adduct formation constant of MLA(2) with L in benzene.     

Extraction equilibria of various metal picrates with 19-crown-6 between benzene and water. Effect of the extra methylene group on extraction ability and selectivity

The overall extraction equilibrium constants (K(ex)) of picrates of Li(+), Na(+), K(+), Rb(+), Cs(+), Ag(+), Tl(+), and Sr(2+)with 19-crown-6 (19C6) were determined between benzene and water at 25 degrees C. The K(ex) values were analyzed into the constituent equilibrium constants, i.e. the extraction constant of picric acid, the distribution constant of the crown ether, the formation constant of the metal ion-crown ether complex in water, and the ion-pair extraction constant of the complex cation with the picrate anion. The effects of an extra methylene group of 19C6 on the extraction ability and selectivity are discussed in detail by comparing the constituent equilibrium constants of 19C6 with those of 18-crown-6 (18C6). The K(ex) value of 19C6 for each metal ion is lower than that of 18C6, which is mostly attributed to the higher lipophilicity of 19C6. The extraction ability of 19C6 for the univalent metal ions decreases in the order Tl(+)>K(+)>Rb(+)>Ag(+)>Cs(+)>Na(+)Li(+), which is the same as that observed for 18C6. The difference in logK(ex) between the univalent metals is generally smaller for 19C6 than for 18C6. The extraction selectivity of 19C6 is governed by the selectivity in the ion-pair extraction, whereas that of 18C6 depends on both the selectivities in the ion-pair extraction and in the complexation in water.     

Extraction of Alkali Metal (Na—Cs) Picrates with Dibenzo-18-crown-6 into Various Organic Solvents. Elucidation of Fundamental Equilibria which Govern the Extraction-Ability and -Selectivity

In order to quantitatively investigate effects of the size, the structuralrigidity, and the lipophilicity of dibenzo-18-crown-6 (DB18C6) on itsextraction-ability and -selectivity for alkali metal ions, constants of theoverall extraction (Kex), the distribution for various diluents of lowdielectric constants (K_D,MLA), and the aqueous ion-pairformation (K_MLA) of DB18C6-alkali metal (Na-—Cs) picrate 1:1:1 complexes were determined at 25°C; the partition constants of DB18C6 itself were also measured at 25°C. The log K_MLA of Na, K, Rb, and Cs are -0.14 ± 0.11, 1.30 ± 0.10, 1.00 ± 0.09, and 0.24 ± 0.11, respectively. The partition behavior of DB18C6 and its1:1:1 complexes with the alkali metal picrates can be clearly explained byregular solution theory, except for chloroform. The molar volumes andsolubility parameters of DB18C6 and the 1:1:1 complexes were determined.A relation between molar volumes of the complexes and K_MLAis discussed. The magnitude of Kex is largely determined by that ofK_D,MLA. For every diluent, the extraction selectivity of DB18C6increases in the order Na > Cs > Rb > K. The K extraction-selectivity of DB18C6 over Na is the highest among all the combinations of the two neighboring alkali metals in the periodic table. The extraction-ability and -selectivity for the alkalimetal picrates and their change with the diluent of DB18C6 were completely elucidated by the four fundamental equilibria and regular solution theory.     

Thermodynamic study of solvent extraction of 15-crown-5- and 18-crown-6-s-block metal ion complexes and tetraalkylammonium ions with picrate anions into chloroform

Enthalpy and entropy changes for ion-pair extractions of tetraalkylammonium ions (R(4)N(+)) with picrate anions, overall extractions of s-block metal picrates with 15-crown-5 (15C5) and 18-crown-6 (18C6) and the partition of 15C5 itself were determined between chloroform and water. The distribution behaviour of crown ethers and the extraction process of s-block metal picrates with the crown ethers are discussed in detail on molecular grounds from the thermodynamic point of view. Moreover, enthalpy and entropy changes for ion-pair extractions of 1:1 15C5- and 18C6-s-block metal ion complexes with picrate anions are calculated from these experimental thermodynamic parameters and the literature values for complex-formation reactions of the crown ethers with the s-block metal ions in water. Enthalpy and entropy changes are negative for overall extractions of all the s-block metal picrates with 15C5 and 18C6. The extractions of the metal picrates with 15C5 and 18C6 at 25 degrees are completely enthalpy driven. Plots of thermodynamic parameters for ion-pair extractions of R(4)NA vs. the number of carbon atoms of R(4)N(+) show a linear relationship. From these experimental data, contributions of a methylene group and an ether oxygen atom to the thermodynamic parameters of the ion-pair extraction of R(4)NA and the partition of the crown ethers, respectively, between chloroform and water were obtained. Enthalpy and entropy changes for ion-pair extractions of 15C5- and 18C6-s-block metal picrate complexes were compared with those of R(4)NA. A striking difference in the ion-pair extraction process was found between the crown ether complexes and R(4)NA.     

Conductance study of the complexation of substituted and lariat 16-crown-5 derivatives with alkali metal ions in nonaqueous solvents

Formation constants (K _ML) of 1:1 complexes of 15-(2,5-dioxahexyl)-15-methyl-16-crown-5 (L16C5) and 15,15-dimethyl-16-crown-5 (DM16C5) with alkali metal ions were determined in acetonitrile (AN) and propylene carbonate (PC) by conductometry at 25°C. Except for the case of Li⁺-and K⁺-16C5 complexes in PC, the selectivity sequences of L16C5 and DM16C5 are identical with those of the parent crown ether 16-crown-5 (16C5) regardless of the solvent (AN, PC, methanol) (Na¹ > Li⁺ > K⁺ > Rb⁺ > Cs⁺), which show the size-fit correlation. The selectivities of L16C5 and DM16C5 for the alkali metal ions are governed not by the sidearms but by the cavity size. The stability of the crown ether complex is dependent not on the dielectric constant but largely on the donor number of the solvent. TheK _ML(M₁ ⁺)/K _ML(M₂ ⁺) ratio of L16C5 or 16C5 varies very much with the solvent in the cases of M₁=Na, M₂=K and M₁=Na, M₂=Li, but that of DM16C5 is almost constant regardless of the solvent.     

Evaluation of selectivity-determining factors for membrane electrodes based on naphtho-15-crown-5 by liquid-liquid extraction

Liquid-liquid extractions of sodium and potassium picrates with naphtho-15-crown-5 (N15C5) into 1,2-dichloroethane are studied, in order to clarify the factors governing the high potassium ion selectivity of the N15C5-based membrane electrode. The distribution coefficient of N15C5 between water and 1,2-dichloroethane was 1800 at 15°C. The formation constants of the complexes of N15C5 with the sodium ion and the potassium ion in the aqueous phase were less than unity and there was no remarkable difference between their values. Potassium picrate was mainly extracted into 1,2-dichloroethane by forming the 2:1 N15C5-potassium complex, while sodium picrate was extracted by forming the 1:1 complex. The extraction constants for sodium picrate and potassium picrate were 10^3.86 and 10^7.61, respectively, The high potassium selectivity is concluded to be due to the high extractability of the 2:1 potassium complex.     

Extraction Equilibria between Benzene and Water of Uni- and Bivalent Metal Picrates with Lariat 16-Crown-5: Effect of the Side Arms on the Extraction Ability and Selectivity

The overall extraction constants (K_ex) of uni- andbivalent metal picrates with 15-(2,5-dioxahexyl)-15-methyl-16-crown-5(L16C5) were determined between benzene and water at 25°C. TheK_ex values were analyzed into the constituent equilibriumconstants, i.e., the extraction constant of picric acid, the distributionconstant of the crown ether, the stability constant of the metalion–crown ether complex in water, and the ion-pair extraction constantof the complex cation with the picrate anion. The K_ex valuedecreases in the orders Ag⁺ > Na⁺ >Tl⁺ > K⁺ > Li⁺ andPb²⁺ > Ba²⁺ > Sr²⁺ for theuni- and bivalent metals, respectively, which are the same as those observedfor 16C5. The extraction selectivity was found to be governed by theselectivity of the ion-pair extraction of the L16C5–metal picratecomplex rather than by that of the complex formation in water. Theextraction ability of L16C5 is smaller for all the metals than that of 16C5,which is mostly attributed to the higher lipophilicity of L16C5. Differencesin the extraction selectivity between L16C5 and 16C5 were observed for thebivalent metals but little for the univalent metals. The side-arm effect onthe extraction selectivity was interpreted on the basis of the negativecorrelation between the effect on the complex stability constant in waterand that on the ion-pair extraction constant.     

Ion-pair extraction of Na(+), K(+) and Ca(2+) with some organic counter-ions and dicyclohexyl-18-crown-6 as adduct-forming reagent

Extraction equilibria of ion-pairs formed by the Na(+), K(+) and Ca(2+) complexes of dicyclohexyl-18-crown-6 and beta- and gamma-dinitrophenol, picric acid and dipicrylamine have been studied in the two-phase system H(2)O/CH(2)Cl(2). Extraction constants and dissociation constants for the ion-pairs in the organic phase are given and show that the efficiency of extraction increases with the hydrophobicity of the counter-ion. At the same time, the selectivity decreases.     

Design and synthesis of luminescence chemosensors based on alkynyl phosphine gold(I)-copper(I) aggregates

Receptor-containing polynuclear mixed-metal complexes of gold(I)-copper(I) 1-3 based on a [{Au(3)Cu(2)(C≡CPh)(6)}Au(3){PPh(2)-C(6)H(4)-PPh(2)}(3)](2+) (Au(6)Cu(2)) core with benzo-15-crown-5, oligoether and urea binding sites were designed and synthesized, respectively. These complexes exhibited remarkably strong red emission at ca. 619-630 nm in dichloromethane solution at room temperature upon photoexcitation at λ > 400 nm, with the emission quantum yield in the range 0.59-0.85. The cation-binding properties of 1 and 2 and the anion-binding properties of 3 were studied using UV-vis, emission and (1)H NMR techniques. Complex 1, with six benzo-15-crown-5 pendants, was found to show a higher binding preference for K(+), with a selectivity trend of K(+)? Cs(+) > Na(+) > Li(+). The addition of metal ions (Li(+), Na(+), K(+) and Cs(+)) to complex 1 led to a modest emission enhancement with a concomitant slight blue shift in energy and well-defined isoemissive points, which is attributed to the rigidity of the structure and the inhibited PET (photo-induced electron transfer) process from the oxygen to the aggregate as a result of the binding of the metal ion. The six urea receptor groups on complex 3 were found to form multiple hydrogen bonding interactions with anions, with the positive charge providing additional electrostatic interaction for anion-binding. The anion selectivity of 3 follows the trend F(-) > Cl(-)≈ H(2)PO(4)(-) > Br(-) and the highest affinity towards F(-) is attributed to the stronger basicity of F(-), as well as its good size match with the cavity of the urea pocket.     

Solvent extraction of univalent and bivalent metal picrates with 1,2-bis[2-(2-methoxyethoxy)ethoxy] benzene (noncyclic crown ether) into CHCl3

The overall extraction equilibrium constants, K_ex, of 1:1:m complexes of 1,2-bis[2-(2-methoxyethoxy)ethoxyjbenzene (AC · B18C6) with uni- and bivalent metal picrates, MA _m were determined at 25°C between CHCl₃ and water, and thereby the ion-pair complex-formation constants,K _MLA,o, of AC · B18C6 with the univalent metal picrates in CHCl₃ were calculated. The AC · B18C6 is an open-chain analog of benzo-18-crown-6 (B18C6). The equilibrium constants of AC · B18C6 were compared with those of B18C6. K_ex sequences of AC · B18C6 for uni- and bivalent metals are Tl⁺ > K⁺ > Rb⁺ > Cs⁺ > Na⁺ > Li⁺ and Pb²⁺ > Ba²⁺ > Sr²⁺, respectively. The same extraction-selectivity was observed for B18C6, but the extractability of AC · B18C6 for the same cation is much lower than that of B18C6; the extraction selectivity of AC · B18C6 for alkali metals is lower than that of B18C6. TheK _MLA,o sequence of AC · B18C6 is K⁺ > Rb⁺ > Tl⁺ > Cs⁺ Na⁺, which is consistent with that of B18C6. ButK _MLA,o of AC · B18C6 is much smaller than the correspondingK _MLA,o of B18C6; the selectivity of AC · B18C6 among alkali metal picrates in CHCl₃ is lower than that of BI8C6. This reflects the difference in the structures between AC · B18C6 (acyclic and flexible) and B18C6 (cyclic and rigid).     

冠醚配合物热力学性质的研究 X: 用NMR研究15-冠-5-衍生物与钠离子的配位反应

用^2^3Na NMR研究了15-冠-5(15C5), 2,3-苯并-15-冠-5(B-15C5), 2,3-苯并-6-甲基-15-冠-5(BCl-15C5), 2,3-苯并-8,12-二甲基-15-冠-5(BC2-15C5)在丙酮中与Na^+的配位反应, 由此探索甲基的影响, 实验结果表明, 当在金属盐溶液中加入冠醚, 配体为15C5时, 体系表观化学位移移至低场, 配体为B-15C5, BC1-15C5, BC2-15C5时, 体系在表观化学位移移至高场, 后者与苯并-18-冠-6及其甲基衍生物不同, 这是由于苯环在空间排布不同所致, 用Newton-Raphson法和描坑法(Pit-mapping)拟合实验数据, 发现BC1-15C5和BC2-15C5除形成NaL^+和NaL2^+外还有不稳定的Na3L2^3^+形成。本文对形成过程和生成NaL^+反应的平衡常数lgK11与甲基数的关系亦作了讨论, lgK11与甲基数目n近似成直线关系, 可用下式表示: lgK11=3.50-0.80n, n=0,1,2。