Bestimmung des Enantiomerenüberschusses von chiralen Ammonium‐Ionen mit Hilfe von Flüssigmembranelektroden

Abstract

A cell assembly with two membranes each containing one enantiomer of a chiral ionophore is described. It is suitable for the direct potentiometric determination of the enantiomeric excess of ions. The method is used to determine the enantiomeric excess of ephedronium ions in aqueous solutions.

Carrier-Based Ion-Selective Electrodes and Bulk Optodes. 2. Ionophores for Potentiometric and Optical Sensors

“…It was followed by many other enantioselective ISEs, often based on ionophores that were not specifically developed for potentiometry. Using noncyclic diamides, , crown ethers, − cyclodextrins, − tartaric acid esters (the latter as chiral plasticizers), , and derivatives of monensin ,,, and other antibiotics, enantioselectivities for 1-phenylethylamine ( A-1 ), − ,− ,, 1-(1-naphthyl)-ethylamine ( A-2 ), ,, ephedrine ( A-3 ), ,,,,, norephedrine ( A-4 ), ,, pseudoephedrine ( A-5 ; also called Ψ-ephedrine), ,,, amphetamine ( A-6 ), , propranolol ( A-7 ), amino acid methyl esters, ,,− ,, α-amino-ε-caprolactam ( A-8 ), and amino acid amides 902 were determined (Chart 1). While several of the ISEs based on these ionophores would probably yield interesting selectivities toward other, nonenantiomeric organic cations, with few exceptions (such as for three crown ethers (e. g. AM-1 ) 904 or for the cyclodextrins AM-3 and AM-4 (Chart 1); ,…”

Enantiomeric Recognition of Amine Compounds by Chiral Macrocyclic Receptors

“…Based on the locking mechanism, Still and coworkers synthesized a series of tetracyclic (218)(219)(220)(221)(222)(223)(224)(225)(226)(227)(228)(229)(230)(231)(232)(233)(234)(235)(236) and hexacyclic (237 and 238) podands and studied their enantioselection properties. [258][259][260][261][262][263][264][265][266][267][268] These podands are conformationally locked into particular geometries and display high enantioselectivity.…”

Elektromotorisches Verhalten von Flüssigmembranelektroden‐Messketten mit enantiomerenselektiven chiralen Ionophoren

“…Dabei ging es einerseits darum, mittels potentiometrischer Messungen die Selektivitat solcher Systeme fur enantiomere lonen zu charakterisieren, und andererseits wurden Moglichkeiten von analytischen Anwendungen entsprechender Messmethoden aufgezeigt. Wahrend die fruheren experimentellen Ergebnisse auf der Grundlage eines einfachen Membranmodells [2] [5] (6) 1 E = const + s . log X (u, + C C u, , , pMLn c,") kMaM …”

“…Es ist ersichtlich, dass bei Messungen an (f)-Ephedriniumlosungen eine signifikant von null abweichende Potentialdifferenz beobachtet wurde. Dieser experimentelle Befund steht in krassem Widerspruch zum entsprechenden Ergebnis einer fruheren Modellbetrachtung [5] (Annahme einer 1 : 1 -Komplexstochiometrie, vgl. GZeichung 27).…”