Crown Ethers with Fluctuating Ring Size (“Breathing Crown Ethers”)

1979 ◽  
Vol 18 (4) ◽  
pp. 311-312 ◽  
Author(s):  
Gerhard Schröder ◽  
Walter Witt
Keyword(s):  
Crown Ethers ◽  
Ring Size

Distribution of benzo-substituted crown-ethers between chloroform and water: effects of macrocycle ring size and lithium chloride

2018 ◽  
Vol 316 (2) ◽  
pp. 535-541 ◽  
Author(s):  
Olga A. Zakurdaeva ◽  
Andrey F. Asachenko ◽  
Maxim A. Topchiy ◽  
Sergey V. Nesterov
Keyword(s):  
Crown Ethers ◽  
Lithium Chloride ◽  
Ring Size ◽  
Water Effects

Extraction of Technetium as [Tc(II)(NO)(AHA)2H2O]+ Species in the UREX Process

2009 ◽  
Author(s):  
Patricia Paviet-Hartmann ◽  
Ana Nunez Gomez-Aleixandre ◽  
Joshua Pak ◽  
Amparo Glez Espartero ◽  
Frederic Poineau ◽  
...  
Keyword(s):  
Phase Composition ◽  
Nitric Acid ◽  
Distribution Coefficient ◽  
Recent Work ◽  
Crown Ethers ◽  
Organic Phase ◽  
Dielectric Constants ◽  
Acetohydroxamic Acid ◽  
Ring Size ◽  
Reductive Nitrosylation

As it is envisioned today, the first segment of the UREX+ process uses low nitric acid concentrations for U(VI) extraction where pertechnetate anion, TcO4−, can be co-extracted with the uranyl and nitrate into TBP-hydrocarbon solutions. A reductant complexant, acetohydroxamic acid (AHA) is added to the process through the scrub to limit the extractability of plutonium and neptunium. Recent work performed in our laboratory (Ref. 1) demonstrated that TcO4− undergoes reductive nitrosylation by AHA under a variety of conditions. The resulting divalent technetium is complexed by AHA to form the pseudo-octahedral trans-aquonitrosyl-(diacetohydroxamic)-technetium(II) complex ([Tc(II)(NO)(AHA)2H2O]+). In this paper, we are reporting the extraction of [Tc(II)(NO)(AHA)2H2O]+ complex by new designed macrocompounds as well as commercially available crown ethers from 18-crown-6 to 24-crown-8 in ring size and of varying derivatization. Several organic diluents with different dielectric constants are used to enhance the distribution coefficient of technetium (II). The experimental efforts are focused on determining the best extraction conditions by varying the macrocomponds nature and concentration, and the organic phase composition.

Influence of the ring size in diphosphorylated dibenzo crown ethers on extraction of metals from nitric acid solutions

2010 ◽  
Vol 52 (4) ◽  
pp. 363-365
Author(s):  
V. V. Yakshin ◽  
O. M. Vilkova ◽  
N. A. Tsarenko ◽  
L. I. Atamas’ ◽  
I. G. Tananaev ◽  
...  
Keyword(s):  
Nitric Acid ◽  
Crown Ethers ◽  
Ring Size ◽  
Acid Solutions ◽  
Nitric Acid Solutions ◽  
Extraction Of Metals

scholarly journals The effect of ring size variation on the structure and stability of lanthanide(iii) complexes with crown ethers containing picolinate pendants

2011 ◽  
Vol 40 (2) ◽  
pp. 384-392 ◽  
Author(s):  
Adrián Roca-Sabio ◽  
Marta Mato-Iglesias ◽  
David Esteban-Gómez ◽  
Andrés de Blas ◽  
Teresa Rodríguez-Blas ◽  
...  
Keyword(s):  
Crown Ethers ◽  
Size Variation ◽  
Ring Size ◽  
Structure And Stability

scholarly journals Effect of crown ether ring size on binding and fluorescence response to saxitoxin in anthracylmethyl monoazacrown ether chemosensors

2006 ◽  
Vol 84 (10) ◽  
pp. 1273-1279 ◽  
Author(s):  
Hua Mao ◽  
John B Thorne ◽  
Jennifer S Pharr ◽  
Robert E Gawley
Keyword(s):  
Detection Limit ◽  
Crown Ether ◽  
Crown Ethers ◽  
Binding Constant ◽  
Binding Constants ◽  
Ring Size ◽  
Paralytic Shellfish Poison ◽  
Fluorescence Response ◽  
Paralytic Shellfish ◽  
Synthetic Routes

Convenient macrocyclization synthetic routes for the preparation of different-sized monoaza anthracylmethyl crown ether chemosensors (15-crown-5, 18-crown-6, 21-crown-7, 24-crown-8, and 27-crown-9) are described. Evaluation of these crowns as chemosensors for saxitoxin revealed that the larger crowns have moderately higher binding constants, with the 27-crown-9 chemosensor having the largest binding constant (2.29 × 105 (mol/L)–1). Fluorescence enhancements of 100% were observed at saxitoxin concentrations of 5 µmol/L, which is close to the detection limit in mouse bioassay.Key words: anthracene, crown ethers, saxitoxin, paralytic shellfish poison (PSP), binding constants; chemosensors.

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