Binding of cyclic polyethers to ion pairs of carbanion alkali salts

Wong, Kevin; Konizer, George B.; Smid, Johannes

doi:10.1021/ja00706a039

Cited by 125 publications

(30 citation statements)

References 2 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Tough membranes were obtained by casting the polymer from salt containing HMPA (e.g., a 1:l ratio of NaSCN to crown ligand). The activation energy of this reaction is about 12 kcal/mol (46,62). Water permeability (= lo-' cm2 9-l) far exceeds that of the salt (lO-'O to lo-" cm2 d).…”

Section: I11mentioning

confidence: 96%

Ion-Binding Properties of Crown Ether and Cryptand Containing Polymers

Smid¹

1980

Ind. Eng. Chem. Prod. Res. Dev.

View full text Add to dashboard Cite

The ion-binding properties of linear and network polymers with macroheterocyclic ligands (crown ethers, cryptands) in the backbone or as pendant group are briefly reviewed. Discussed are the extraction and transport of cations, cation effects on the viscosity of the polymer solutions. ion separation and catalytic behavior of the materials in both aqueous and nonaqueous media, and the formation of polysail complexes. The properties of the materials are determined not only by the cation-binding characteristics of the particular ligand anchored to the polymer chain but also by the spacing between ligands, the nature of comonomer substituents, and, for pendant ligands, on the distance between ligand and the macromolecular backbone. The polysoap character of some of the aqueous poly(crown ether) solutions leads to cation-controlled binding and catalysis of anionic organic solutes

show abstract

Section: I11mentioning

confidence: 96%

Ion-Binding Properties of Crown Ether and Cryptand Containing Polymers

Smid¹

1980

Ind. Eng. Chem. Prod. Res. Dev.

View full text Add to dashboard Cite

show abstract

“…The much higher Ke values for the K-18C6 systems as compared to the corresponding Na systems (nearly a factor of 100) are most likely due to a much higher partition coefficient, k, for the potassium picrate. The crown ether dibenzo-18-crown-6 intrinsically appears to bind Na + ions better than K + ions, although this is reversed in the better cation solvating media such as oxetane or methanol [8,30].…”

Section: Extraction Equilibriamentioning

confidence: 99%

“…This is especially the case with the planar crown ethers where complexation can lead to different ion pair structures for the two salts. The selectivity ratio in such mixtures is also likely to be solvent dependent [30]. However, the differences are found to be small when complexing agents such as macrotetralide actin antibiotics are used [7].…”

Section: Transport Measurementsmentioning

confidence: 99%

Ion transport through liquid membranes facilitated by crown ethers and their polymers

1974

Self Cite

View full text Add to dashboard Cite

Summary. The macrocyclic polyethers 4'-methylbenzo-15-crown-5 (15C5) and 4'-methylbenzo-18-crown-6 (18C6) as well as the corresponding crown polymers and crown-styrene copolymers were used as carriers for the transport of sodium and potassium picrate or the corresponding chlorides across a stirred chloroform membrane. The observation of pronounced bathochromic shifts in the optical spectra of picrate salts on increasing the interionic ion pair distance could be utilized in determining the nature and structure of the migrating species. These species were found to be ion pair crown complexes of at least two kinds, viz., crown-complexed tight ion pairs and crown-separated ion pairs. The feasibility to thus identify the detailed structure of the migrating ionic entity is important as solvents of low polarity such as chloroform or hexane have been used as liquid membranes to represent the interior of biomembranes. The structure of the ion pair is expected to be an important consideration in correlating properties such as membrane potentials or cation selectivities with ionic distribution equilibria. Ion pair extraction equilibrium constants were determined in the H20-CHC1 a system for the various crown species. The values for 18C6 with sodium and potassium picrate are nearly the same as those for the corresponding polymers. The same was found with 15C5 and sodium picrate; but the potassium forms, in addition to a 1:1 complex, a 1:2 complex with 15C5, making the corresponding polymer a more effective extracting agent. The ionic distribution data were interpreted in terms of the salt partition coefficients and the complex formation constants of the ion pair crown complexes in chloroform. The salt migration across the liquid membrane was found to be controlled by the diffusion of the ion pair complex in the chloroform, the extraction equilibrium across the interphase being rapidly established. The thickness of the diffusion layer adjacent to the water-chloroform interphase was estimated to be 50 la. The ratios of the salt fluxes under otherwise identical conditions were found to be governed by the extraction equilibrium constants, the selectivity ratio for the potassium-to-sodium picrate with 18C6 being 118. This ratio, which was also determined for other crown species, was found to be anion dependent.Ion transport across membranes is known to be augmented by macrocyclic antibiotics such as monactin and valinomycin [1,6,7,9,15,28]. This

show abstract

“…51). This may be an oversimplification, and the roles of solvation, aggregation and the formation of contact and solvent-separated ion pairs have to be considered ; (21 ' 26a ' 49a ' 55) nevertheless, in the presence of strongly cation solvating media such as the "crown ethers" a high degree of ionisation is likely/ 22 ' 38 ' 114) The propagating species in the organolithium-initiated polymerisation of dienes are allyl-lithium derivatives (see Section 7. ionic structures (I) in ethereal solvents. For example, the J H n.m.r.…”

Section: Structure Of Benzylic and Ally Lie Organolithium Compoundsmentioning

confidence: 99%

The Constitution of Organolithium Compounds

Wakefield

1974

The Chemistry of Organolithium Compounds

View full text Add to dashboard Cite

Binding of cyclic polyethers to ion pairs of carbanion alkali salts

Cited by 125 publications

References 2 publications

Ion-Binding Properties of Crown Ether and Cryptand Containing Polymers

Ion-Binding Properties of Crown Ether and Cryptand Containing Polymers

Ion transport through liquid membranes facilitated by crown ethers and their polymers

The Constitution of Organolithium Compounds

Contact Info

Product

Resources

About