scholarly journals Enhancement of Ion Pairing of Sr(II) and Ba(II) Salts by a Tritopic Ion‐Pair Receptor in Solution

ChemPhysChem ◽  
2020 ◽  
Vol 21 (17) ◽  
pp. 1957-1965
Author(s):  
Bence Kutus ◽  
Jun Zhu ◽  
Jian Luo ◽  
Qi‐Qiang Wang ◽  
Alexandru Lupan ◽  
...  
Keyword(s):  
2011 ◽  
Vol 324 ◽  
pp. 166-169 ◽  
Author(s):  
Farah Zeitouni ◽  
Gehan El-Subruiti ◽  
Ghassan Younes ◽  
Mohammad Amira

The rate of aquation of bromopentaammine cobalt(III) ion in the presence of different types of dicarboxylate solutions containing tert-butanol (40% V/V) have been measured spectrophotometrically at different temperatures (30-600°C) in the light of the effects of ion-pairing on reaction rates and mechanism. The thermodynamic and extrathermodynamic parameters of activation have been calculated and discussed in terms of solvent effect on the ion-pair aquation reaction. The free energy of activation ∆Gip* is more or less linearly varied among the studied dicarboxylate ion-pairing ligands indicating the presence of compensation effect between ∆Hip* and ∆Sip*. Comparing the kip values with respect of different buffers at 40% of ter-butanol is introduced.


2000 ◽  
Vol 53 (5) ◽  
pp. 363 ◽  
Author(s):  
Steven Kratsis ◽  
Glenn Hefter ◽  
Peter M. May ◽  
Pal Sipos

The protonation constant (pKa) of SO42–(aq) has been determined at ionic strengths 0.5 M ≤I ≤4.0 M in NaCl and CsCl media at 25˚C by using Raman spectroscopy. These data were used to calculate the association constant of the NaSO4–(aq) ion pair in CsCl media. The results are in excellent agreement with previous values obtained by other techniques. The (pKa) was also measured at I = 4 M in both media at temperatures up to 85˚C and the associated enthalpy and entropy changes were calculated. However, reliable thermodynamic data for the ion-pairing reaction could not be obtained at higher temperatures probably because of competition from CsSO4–(aq).


1998 ◽  
Vol 81 (2) ◽  
pp. 349-358 ◽  
Author(s):  
Thomas M Primus ◽  
Doreen L Griffin ◽  
Stephanite A Volz ◽  
John J Johnston

abstract A reversed-phase ion-pair liquid chromatographic (LC) method was developed for analysis of steam-rolled oat (SRO) baits fortified with either chlorophacinone or diphacinone. Baits were prepared with and without paraffin wax. Chlorophacinone or diphacinone was extracted from wax-free SRO baits with 5 mM tetrabutylammonium phosphate methanolic ion-pairing solution. Wax baits were initially extracted with petroleum ether and then cleaned up by liquid extraction into methanolic ion-pairing solution containing 20% water. SRO extracts were analyzed with reversed-phase ion-pair LC. Chlorophacinone and diphacinone were quantified by UV absorption at 325 nm. Recoveries from SRO fortified with chlorophacinone at 25 and 150 μg/g were 90.7 and 90.8%, respectively, whereas for diphacinone at the same levels, recoveries were 93.5 and 92.3%, respectively. Recoveries from wax baits fortified at 25 and 75 μg/g chlorophacinone were 98.5 and 100%, respectively, whereas for diphacinone at the same levels, recoveries were 93.6 and 98.0%, respectively. Method limits of detection for chlorophacinone and diphacinone in SRO baits were estimated to be 1.0 and 0.76 μg/g, respectively. Method limits of detection for chlorophacinone and diphacinone in wax baits were estimated to be 4.2 and 2.8 μg/g, respectively.


2001 ◽  
Vol 84 (3) ◽  
pp. 634-639 ◽  
Author(s):  
John J Johnston ◽  
Margaret J Goodall ◽  
Jerome C Hurley ◽  
Christi A Yoder ◽  
Lowell A Miller

Abstract Liquid chromatographic (LC) methods were developed for quantitating the potential avian contraceptive DiazaCon in quail feed and serum. DiazaCon was extracted from ground quail feed with basic n-butyl chloride. The n-butyl chloride extract was evaporated to dryness. The DiazaCon residues were dissolved in an aqueous methanolic ion pairing solution and quantitated by LC at 206 nm. Avian sera was combined with an equal volume of a pH 4 aqueous solution of ion pairing reagent and filtered to remove interfering proteins. DiazaCon was quantitated by LC. Mean recoveries for 500 and 2000 ppm fortified feed were 89.1 and 91.0%, respectively. The mean recovery for sera fortified at 5 levels ranging from 35 to 2000 ppm was 84.9%. Method limits of detection were approximately 14 and 13 ppm for feed and sera, respectively.


2021 ◽  
Author(s):  
Matej Žabka ◽  
Ruth M. Gschwind

In ion pairing catalysis, the structures of advanced intermediates are often not accessible. Here, we present a combined experimental and computational study of ternary complexes in Brønsted acid catalysis, which show unexpected H-bond switching.


1989 ◽  
Vol 67 (1) ◽  
pp. 21-26 ◽  
Author(s):  
Zhu-Gen Lai ◽  
Kenneth Charles Westaway

The secondary α-deuterium kinetic isotope effects and substituent effect found in the SN2 reactions between a series of para-substituted sodium thiophenoxides and benzyldimethylphenylammonium ion are significantly larger when the reacting nucleophile is a free ion than when it is a solvent-separated ion pair complex. Tighter transition states are found when a poorer nucleophile is used in both the free ion and ion pair reactions. Also, the transition states for all but one substituent are tighter for the reactions with the solvent-separated ion pair complex than with the free ion. Hammett ρ values found by changing the substituent on the nucleophile do not appear to be useful for determining the length of the sulphur–α-carbon bond in the ion pair and free ion transition states. Keywords: Isotope effects, ion pairing, nucleophilic substitution, SN2 reactions, transition states.


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