Use of metal ion catalysis in detection and determination of microamounts of complexing agents. Determination of ethylenediamine-N,N,N',N'-tetraacetic acid

1967 ◽  
Vol 39 (11) ◽  
pp. 1294-1297 ◽  
Author(s):  
Horacio A. Mottola ◽  
Henry. Freiser
Keyword(s):  
Metal Ion ◽  
Complexing Agents ◽  
Tetraacetic Acid ◽  
Metal Ion Catalysis

Metal ion catalysis in nucleophilic displacement reactions at carbon, phosphorus, and sulfur centers. I. Catalysis by metal ions in the reaction of p-nitrophenyl diphenylphosphinate with ethoxide

1989 ◽  
Vol 67 (9) ◽  
pp. 1440-1448 ◽  
Author(s):  
Edward J. Dunn ◽  
Erwin Buncel
Keyword(s):  
Crown Ether ◽  
Alkali Metal ◽  
Transition State ◽  
Metal Ions ◽  
Ground State ◽  
Metal Ion ◽  
Complexing Agents ◽  
Transition State Stabilization ◽  
Nucleophilic Displacement ◽  
Metal Ion Catalysis

The effect of macrocyclic crown ether and cryptand complexing agents on the rate of the nucleophilic displacement reaction of p-nitrophenyl diphenylphosphinate by alkali metal ethoxides in ethanol at 25 °C has been studied by spectrophotometric techniques. For the reactions of potassium ethoxide, sodium ethoxide, and lithium ethoxide, the observed rate constant increased in the order KOEt < NaOEt < LiOEt. Crown ether and cryptand cation-complexing agents have a retarding effect on the rate. Increasing the ratio of complexing agent to base results in a decrease in kobs to a minimum value corresponding to the rate of reaction of free ethoxide ion. In complementary experiments, alkali metal ions were added to these reaction systems in the form of unreactive salts, causing an increase in reaction rate. The kinetic data were analysed in terms of ion-pairing treatments, which allowed evaluation of rate coefficients due to free ethoxide ions and metal ion – ethoxide ion pairs. Possible roles of the metal cations are discussed in terms of ground state and transition state stabilization. Evaluation of the equilibrium constants for association of the metal ion with ground state (Ka) and the transition state (K′a) shows that catalysis occurs as a result of enhanced association between the metal ion and the transition state, with (K′a) values increasing in the order K+ < Na+ < Li+. A model is proposed in which transition state stabilization arises largely from chelation of the solvated metal ion to two charged oxygen centers. This appears to be the first reported instance of catalysis by alkali metal cations in nucleophilic displacement at phosphoryl centers. Keywords: nucleophilic displacement at phosphorus, alkali-metal-ion catalysis.

scholarly journals Metal ion catalysis in nucleophilic displacement reactions at carbon, phosphorus, and sulfur centers. II. Metal ion catalysis in the reaction of p-nitrophenyl diphenylphosphinate with alkali metal phenoxides in ethanol

1990 ◽  
Vol 68 (10) ◽  
pp. 1837-1845 ◽  
Author(s):  
Edward J. Dunn ◽  
Robert Y. Moir ◽  
Erwin Buncel ◽  
J. Garfield Purdon ◽  
Robert A. B. Bannard
Keyword(s):  
Alkali Metal ◽  
Transition State ◽  
Metal Ions ◽  
Metal Ion ◽  
Ion Pairs ◽  
Rate Coefficients ◽  
Complexing Agents ◽  
Specific Rate ◽  
Nucleophilic Displacement ◽  
Metal Ion Catalysis

The reactions of p-nitrophenyl diphenylphosphinate (1) with lithium, sodium, potassium, and benzyltrimethylammonium phenoxides (BTMAOPh) have been studied by spectrophotometric techniques in anhydrous ethanol at 25 °C. The reactivity (kobs) of the alkali metal phenoxides increases in the order BTMAOPh < KOPh < NaOPh < LiOPh. The rate of reaction of 1 with LiOPh is enhanced when lithium salts (LiSCN, LiNO3, LiClO4, LiOAc) are added to the reaction media. The addition of the alkali metal complexing agents dicyclohexyl-18-crown-6 ether or [2.2.2]cryptand for Na+, and [2.1.1]cryptand for Li+, to each of the alkali metal phenoxide reactions resulted in a decrease in rate, indicating catalysis by the alkali metal ions. The kinetic data are analyzed to obtain specific rate coefficients of reactions of phenoxide and ethoxide as the dissociated ions and as alkali metal – phenoxide ion pairs. Reactivities follow the order [Formula: see text]; [Formula: see text]; [Formula: see text]; [Formula: see text]. A mechanism is proposed in which the ion-paired metal phenoxide is more reactive towards the substrate than is the dissociated phenoxide. Analysis of the data in terms of initial state and transition state interactions with metal ions indicates that the increased reactivity of the ion-paired species results from greater stabilization of the negatively charged transition state relative to stabilization of the ion-paired nucleophile. Keywords: nucleophilic displacement at phosphorus by phenoxide, alkali-metal-ion catalysis.

The effect of complexing agents in chemical solution deposition of metal chalcogenide thin films

2021 ◽  
Author(s):  
Sucheta Sengupta ◽  
Rinki Aggarwal ◽  
Yuval Golan
Keyword(s):  
Thin Films ◽  
Chemical Solution Deposition ◽  
Metal Ion ◽  
Chemical Deposition ◽  
Review Article ◽  
Complexing Agents ◽  
Chemical Solution ◽  
Solution Deposition ◽  
Metal Chalcogenide ◽  
Chalcogenide Thin Films

This review article gives an overview of different complexing agents used during chemical deposition of metal chalcogenide thin films and their role in controlling the resultant morphology by effective complexation of the metal ion.

Synthesis and characterization of 19F NMR chelators for measurement of cytosolic free Ca

1987 ◽  
Vol 252 (4) ◽  
pp. C441-C449 ◽  
Author(s):  
L. A. Levy ◽  
E. Murphy ◽  
R. E. London
Keyword(s):  
Chemical Shifts ◽  
Cell Types ◽  
Free Calcium ◽  
Tetraacetic Acid ◽  
Nmr Studies ◽  
Cytosolic Free Calcium ◽  
Fluorine Nmr ◽  
Dissociation Constant Kd

Fluorine 19 nuclear magnetic resonance (NMR) studies of intracellular fluorinated calcium chelators provide a useful strategy for the determination of cytosolic free calcium levels in cells and perfused organs. However, the fluorinated chelator with the highest affinity for calcium ions which has been described to date. 1,2-bis-(2-amino-5-fluorophenoxy)ethane-N,N,N',N'-tetraacetic acid (5FBAPTA), exhibits a dissociation constant (Kd) value 5- to 10-fold greater than the intracellular calcium concentration levels in most cell types, thus limiting the ability of fluorine NMR to report these concentrations reliably. We have consequently designed and synthesized several fluorinated calcium chelators with higher affinity for calcium. The best of these, 2-(2-amino-4-methyl-5-fluorophenoxy)-methyl-8 aminoquinidine-N,N,N',N'-tetraacetic acid (quinMF), has a Kd value approximately 10 times lower than that of 5FBAPTA. Several of the newly synthesized indicators have different chemical shifts for the calcium complexed and uncomplexed chelators to allow the simultaneous use of two indicators. In addition to providing information about the level of cytosolic free calcium, chelators containing a quinoline ring exhibit considerable sensitivity to magnesium levels and hence have potential application for the determination of cytosolic-magnesium concentrations. Application of these chelators is illustrated by determination of the cytosolic-free calcium level in erythrocytes. Use of quinMF, the chelator with the lowest Kd value, gives a calcium value of 25-30 nM.

Metal Ion Catalysis in the Hydrolysis of Potassium Ethyl Oxalate

Nature ◽  
1964 ◽  
Vol 204 (4964) ◽  
pp. 1189-1190
Author(s):  
ROBERT W. HAY ◽  
NEIL J. WALKER
Keyword(s):  
Metal Ion ◽  
Metal Ion Catalysis ◽  
Hydrolysis Of

Synthesis of interpenetrating polymer networks as metal ion complexing agents

1986 ◽  
Vol 19 (2) ◽  
pp. 273-280 ◽  
Author(s):  
Spiro D. Alexandratos ◽  
Marc A. Strand
Keyword(s):  
Metal Ion ◽  
Polymer Networks ◽  
Interpenetrating Polymer Networks ◽  
Complexing Agents
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