Free-Energy and Structural Analysis of Ion Solvation and Contact Ion-Pair Formation of Li+ with BF4– and PF6– in Water and Carbonate Solvents

2012 ◽  
Vol 116 (22) ◽  
pp. 6476-6487 ◽  
Author(s):  
Munetaka Takeuchi ◽  
Nobuyuki Matubayasi ◽  
Yasuo Kameda ◽  
Babak Minofar ◽  
Shin-ichi Ishiguro ◽  
...  
Keyword(s):  
Free Energy ◽  
Structural Analysis ◽  
Ion Pair ◽  
Pair Formation ◽  
Ion Solvation ◽  
Ion Pair Formation ◽  
Contact Ion Pair

Sodium–carboxylate contact ion pair formation induces stabilization of palmitic acid monolayers at high pH

2017 ◽  
Vol 19 (16) ◽  
pp. 10481-10490 ◽  
Author(s):  
Ellen M. Adams ◽  
Bethany A. Wellen ◽  
Raphael Thiraux ◽  
Sandeep K. Reddy ◽  
Andrew S. Vidalis ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Palmitic Acid ◽  
Ion Pair ◽  
Pair Formation ◽  
High Ph ◽  
Ion Pair Formation ◽  
Sodium Carboxylate ◽  
Contact Ion Pair ◽  
Theory And Experiments

Theory and experiments show that ion-pair formation drives adsorption of deprotonated fatty acids to the interface.

Direct Observation of Contact Ion-Pair Formation in Aqueous Solution

2009 ◽  
Vol 121 (33) ◽  
pp. 6252-6256 ◽  
Author(s):  
Mark R. Antonio ◽  
May Nyman ◽  
Travis M. Anderson
Keyword(s):  
Aqueous Solution ◽  
Direct Observation ◽  
Ion Pair ◽  
Pair Formation ◽  
Ion Pair Formation ◽  
Contact Ion Pair

Thermodynamics and mechanism of hydrophobic interaction

1977 ◽  
Vol 30 (4) ◽  
pp. 741 ◽  
Author(s):  
DG Oakenfull ◽  
DE Fenwick
Keyword(s):  
Free Energy ◽  
Volume Change ◽  
Hydrophobic Interaction ◽  
Ion Pairs ◽  
Hydrophobic Hydration ◽  
Partial Molar Volumes ◽  
Hydrocarbon Chain ◽  
Ion Pair ◽  
Pair Formation ◽  
Ion Pair Formation

.In the mixed solvent, 0.1 mole fraction ethanol-water, long-chain decyltrimethylammonium carboxylates form ion pairs. Ion-pair association constants (and hence the free energy of ion-pair formation) can be measured conductometrically. It is possible to separate the hydrophobic from the electrostatic contribution to the free energy of ion-pair formation by systematically varying the hydrocarbon chain length. We report measurements of the free energy of hydrophobic interaction (ΔG°HI) over the temperature range 278-328 K. The value of ΔG°HI becomes more negative (stronger hydrophobic interaction) with increasing temperature. The temperature coefficient of ΔG°HI was used to calculate the enthalpy (ΔH°HI) and entropy (ΔS°HI) of hydrophobic interaction. At low temperature the entropic contribution to the free energy is the larger but ΔH°HI, dominates at temperatures above c. 324 K. The volume change of hydrophobic interaction was similarly estimated from the volume change of ion-pair formation. We obtained values of apparent molar volume of the decyltrimethylammonium carboxylates (over a range of concentrations) from very precise density measurements. These could then be combined with the appropriate ion-pair association constant (from the conductance measurements) to give the partial molar volumes of the free ions and the ion pair. Hydrophobic interaction was found to be accompanied by a substantial increase in volume amounting to 10.2 ± 0.3 ml mol-1 for each pair of interacting methylene groups. Our results support the view that hydrophobic interaction occurs with a further ordering of water molecules over and above that which exists in the hydrophobic hydration layer surrounding an isolated hydrophobic molecule.

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