Membrane transport systems. II. Transport of alkali metal ions against their concentration gradients

1981 ◽  
Vol 59 (12) ◽  
pp. 1734-1744 ◽  
Author(s):  
Thomas M. Fyles ◽  
Virginia A. Malik-Diemer ◽  
Dennis M. Whitfield
Keyword(s):  
Alkali Metal ◽  
Metal Ions ◽  
Metal Ion ◽  
Complex Function ◽  
Membrane System ◽  
Ion Concentration ◽  
Transport Systems ◽  
Alkali Metal Ions ◽  
Concentration Gradients ◽  
Membrane Transport Systems

An artificial membrane system based on a series of macrocyclic polyether carriers (crown ethers) is described. Under the influence of a proton gradient the carriers move alkali metal ions from basic to acidic solution through a chloroform membrane phase. Transport occurs against the concentration gradient of the transported ion as a result of a coupled counterflow of protons. Different transport behaviors are observed depending upon the metal ion concentration. At high metal ion concentration the amount transported is a linear function of time; at lower metal ion concentration the amount transported is a complex function of time which may be described as the result of a pair of consecutive first order processes. Effects of metal ion, carrier, and proton concentration on transport rate are considered. The rate increases with increasing metal ion or carrier concentration but is essentially independent of the pH of either aqueous phase. Increased lipophilicity of the carrier also results in a rate increase. Carriers derived from 18-crown-6 transport potassium selectively and all ions more rapidly than 15-crown-5 derivatives which are, however, selective for sodium. The overall efficiency of the system is discussed in terms of competing "leak" reactions, either of cations from the basic phase or of anions from the acidic phase.

scholarly journals Cation-Exchange Properties of CrPO4

2003 ◽  
Vol 21 (2) ◽  
pp. 149-160 ◽  
Author(s):  
S. Mustafa ◽  
S. Murtaza ◽  
A. Naeem ◽  
B. Dilara ◽  
K. Farina
Keyword(s):  
Alkali Metal ◽  
Metal Ions ◽  
Metal Ion ◽  
Ion Concentration ◽  
Alkali Metal Ions ◽  
Alkali Metal Cations ◽  
Titration Curves ◽  
Metal Ion Exchange ◽  
Chromium Phosphate ◽  
Exchange Properties

Alkali metal ion exchange (Li+, Na+ and K+) on chromium phosphate (CrPO4) was studied potentiometrically as a function of temperature and metal ion concentration. The shift in the potentiometric titration curves corresponding to the exchange of alkali metal cations increased with increasing pH and concentration of the metal ions, while the opposite results were obtained by increasing the temperature of the system. The affinity of the exchanger for alkali metal ions was also found to be in the order Li+ > Na+ > K+. The data were employed to evaluate the apparent deprotonation constants of CrPO4 and the corresponding thermodynamic parameters ΔH0, ΔS0 and ΔG0.

Alkali metal ion catalysis in nucleophilic displacement by ethoxide ion on p-nitrophenyl phenylphosphonate: Evidence for multiple metal ion catalysis

2003 ◽  
Vol 81 (1) ◽  
pp. 53-63 ◽  
Author(s):  
Erwin Buncel ◽  
Ruby Nagelkerke ◽  
Gregory RJ Thatcher
Keyword(s):  
Alkali Metal ◽  
Transition State ◽  
Metal Ions ◽  
Metal Ion ◽  
Alkali Metal Ions ◽  
Phosphoryl Transfer ◽  
Alkali Metal Ion ◽  
Nucleophilic Displacement ◽  
Displacement Reactions ◽  
Metal Ion Catalysis

In continuation of our studies of alkali metal ion catalysis and inhibition at carbon, phosphorus, and sulfur centers, the role of alkali metal ions in nucleophilic displacement reactions of p-nitrophenyl phenylphosphonate (PNPP) has been examined. All alkali metal ions studied acted as catalysts. Alkali metal ions added as inert salts increased the rate while decreased rate resulted on M+ complexation with 18-crown-6 ether. Kinetic analysis indicated the interaction of possibly three potassium ions, four sodium ions, and five lithium ions in the transition state of the reactions of ethoxide with PNPP. Pre-association of the anionic substrate with two metals ions in the ground state gave the best fit to the experimental data of the sodium system. Thus, the study gives evidence of the role of several metal ions in nucleophilic displacement reactions of ethoxide with anionic PNPP, both in the ground state and in the transition state. Molecular modeling of the anionic transition state implies that the size of the monovalent cation and the steric requirement of the pentacoordinate transition state are the primary limitations on the number of cations that can be brought to bear to stabilize the transition state and catalyze nucleophilic substitution at phosphorus. The bearing of the present work on metal ion catalysis in enzyme systems is discussed, in particular enzymes that catalyze phosphoryl transfer, which often employ multiple metal ions. Our results, both kinetic and modeling, reveal the importance of electrostatic stabilization of the transition state for phosphoryl transfer that may be effected by multiple cations, either monovalent metal ions or amino acid residues. The more such cations can be brought into contact with the anionic transition state, the greater the catalysis observed.Key words: alkali metal ion catalysis, nucleophilic displacement at phosphorus, multiple metal ion catalysis, phosphoryl transfer.

scholarly journals Interaction of Cu+ with cytosine and formation of i-motif-like C–M+–C complexes: alkali versus coinage metals

2016 ◽  
Vol 18 (10) ◽  
pp. 7269-7277 ◽  
Author(s):  
Juehan Gao ◽  
Giel Berden ◽  
M. T. Rodgers ◽  
Jos Oomens
Keyword(s):  
Alkali Metal ◽  
Metal Ions ◽  
Metal Ion ◽  
Alkali Metal Ions ◽  
Metal Ion Complexes ◽  
Coinage Metals

Dimeric metal ion complexes of cytosine C–M+–C display divergent coordination motifs for coinage versus alkali metal ions.

Preparation, ion-exchange, and electrochemical behavior of Cs-type manganese oxides with a novel hexagonal-like morphology

2007 ◽  
Vol 22 (9) ◽  
pp. 2437-2447 ◽  
Author(s):  
Zong-Huai Liu ◽  
Liping Kang ◽  
Mingzhu Zhao ◽  
Kenta Ooi
Keyword(s):  
Ion Exchange ◽  
Alkali Metal ◽  
Metal Ions ◽  
Metal Ion ◽  
Manganese Oxides ◽  
Thermal Analyses ◽  
Alkali Metal Ions ◽  
Ph Titration ◽  
High Discharge Capacity ◽  
Treated Sample

Cs-type layered manganese oxide with a novel hexagonal-like morphology (Cs–BirMO) was prepared by a solid-state reaction procedure. The Cs+ extraction and alkali–metal ion insertion reactions were investigated by chemical analyses, x-ray analyses, scanning electron microscopy observation, Fourier transform-infrared spectroscopy, thermogravimetric differential thermal analyses, pH titration, and distribution coefficient (Kd) measurements. A considerable percentage (88%) of Cs+ ions in the interlayer sites were topotactically extracted by acid treatment, accompanied by a slight change of the lattice parameters. Alkali–metal ions could be inserted into the interlayer of the acid-treated sample (H–BirMO), mainly by an ion-exchange mechanism. The pH titration curve of the H–BirMO sample showed a simple monobasic acid toward Li+, Rb+, and Cs+ ions, and dibasic acid behavior toward Na+ and K+ ions. The order of the apparent capacity was K+ > Li+ ≈ Na+ ≈ Rb+ ≈ Cs+ at pH < 6. The Kd study showed the selectivity sequence of K+ > Rb+ > Na+ > Li+ for alkali–metal ions at the range of pH <5; H–BirMO sample showed markedly high selectivity for the adsorption of K+ ions. Preliminary investigations of the electrochemical properties of the Li+-inserted sample Li–BirMO(1M, 6d) showed that the obtained samples had a relatively high discharge capacity of 115 mAh g−1 and excellent layered stability.

Confined alkali metal ion in two-dimensional aluminum phosphate promoted activity for condensation of lactic acid to 2,3-pentanedione

2021 ◽  
Author(s):  
Xinli Li ◽  
Ju Zhang ◽  
Yunsheng Dai ◽  
Congming Tang ◽  
Chenglong Yang
Keyword(s):  
Lactic Acid ◽  
Alkali Metal ◽  
Metal Ions ◽  
Metal Ion ◽  
Aluminum Phosphate ◽  
Sustainable Production ◽  
Alkali Metal Ions ◽  
Two Dimensional ◽  
Alkali Metal Ion

The sustainable production of 2,3-pentanedione from bio-lactic acid was investigated over the alkali metal ion intercalated laminar aluminum phosphate. The confined alkali metal ions by the adjacent layers of aluminum...

Alkali metal ion controlled product selectivity during photorearrangements of 1-naphthyl phenyl acylates and dibenzyl ketones within zeolites

2003 ◽  
Vol 81 (6) ◽  
pp. 620-631 ◽  
Author(s):  
M Warrier ◽  
Lakshmi S Kaanumalle ◽  
V Ramamurthy
Keyword(s):  
Alkali Metal ◽  
Metal Ions ◽  
Metal Ion ◽  
Heavy Atom ◽  
Alkali Metal Ions ◽  
Spin Orbit Coupling ◽  
Product Selectivity ◽  
Radical Pairs ◽  
Primary Radical Pair ◽  
Atom Effect

Photochemical behaviors of 1-naphthyl phenyl acylates and dibenzyl ketones included in zeolites have been compared. 1-Naphthyl phenyl acylates while in solution produce eight photoproducts; within NaY it gives a single product. The selectivity is attributed to the restriction brought on the mobility of the primary radical pair by the alkali metal ions present in zeolites. Photochemistry of dibenzyl ketones within NaY reveals that the intersystem crossing in caged radical pairs could be influenced by the heavy alkali metal ions. Structures of complexes among Li+ ion and the guest 1-naphthyl phenyl acetates and dibenzyl ketone computed at the B3LYP level have been useful to understand the origin of the observed product selectivity within zeolites.Key words: photo-Fries reaction, zeolites, cation–π interaction, spin-orbit coupling, heavy atom effect.

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