Ion-Pair Formation of Quaternary Ammonium Salts in Hydrogen-Bonded Solvents

1972 ◽  
Vol 81 (1-4) ◽  
pp. 148-157 ◽  
Author(s):  
F. Accascina ◽  
M. Goffredi ◽  
R. Triolo
Keyword(s):  
Quaternary Ammonium ◽  
Ion Pair ◽  
Pair Formation ◽  
Quaternary Ammonium Salts ◽  
Ammonium Salts ◽  
Ion Pair Formation ◽  
Hydrogen Bonded

scholarly journals Evaluation of Ion-pair Formation of Adefovir to Improve Permeation across Artificial and Biological Membranes

2018 ◽  
Vol 21 ◽  
pp. 160-170 ◽  
Author(s):  
Bahar Darsazan ◽  
Alireza Shafaati ◽  
Afshin Zarghi ◽  
Seyed Alireza Mortazavi
Keyword(s):  
Quaternary Ammonium ◽  
Adefovir Dipivoxil ◽  
Ion Pair ◽  
Pair Formation ◽  
Quaternary Ammonium Salts ◽  
Ammonium Salts ◽  
Apparent Permeability ◽  
Ion Pair Formation ◽  
Counter Ion ◽  
Everted Gut Sac

Purpose: Adefovir is an antiviral drug that exhibits high hydrophilic properties and negligible bioavailability (less than 12%). It is only applied in the form of the ester prodrug adefovir dipivoxil (ADV). The oral bioavailability of ADV is limited (32% to 45%) by its low permeability (Class 3) and biological conversion of the prodrug to adefovir. Ion-pair formation is considered as an alternative approach to a covalent prodrug (ADV) to enhance intestinal permeation of adefovir. Methods: The effect of various counter-ions (anionic, cationic and two quaternary ammonium salts) on the lipophilicity of adefovir was investigated by means of the n-octanol/buffer partitioning system, an in vitro transport model (PAMPA) and a biological membrane (everted gut sac). Results: Quaternary ammonium salts, cetylpyridinium chloride (CPC) and cetrimide enhanced the lipophilicity of adefovir 136- and 87-fold, respectively. The apparent permeability of adefovir in combination with CPC (counter-ion) was 2.5-fold greater than ADV permeability in the PAMPA model. The apparent permeability of adefovir-CPC (counter-ion) was 1.3-fold greater than that of adefovir dipivoxil permeability in a biologic membrane (everted gut sac). Conclusion: These results suggest that the adefovir-CPC ion-paired system has potential for improving the permeation of adefovir across the intestinal membrane. This article is open to POST-PUBLICATION REVIEW. Registered readers (see “For Readers”) may comment by clicking on ABSTRACT on the issue’s contents page.

Electrical conductivities of quaternary ammonium salts in acetone.: Part III. Ion-pair formation

1968 ◽  
Vol 46 (12) ◽  
pp. 2005-2011 ◽  
Author(s):  
W. A. Adams ◽  
K. J. Laidler
Keyword(s):  
Dissociation Constants ◽  
Ion Pairs ◽  
Ion Pair ◽  
Pair Formation ◽  
Quaternary Ammonium Salts ◽  
Acetone Solution ◽  
Ammonium Salts ◽  
Electrical Conductivities ◽  
Tetraethylammonium Iodide ◽  
Kbar Pressure

The ion-pair dissociation constants determined from a Shedlovsky analysis of conductivity (see Part I) were used to calculate the enthalpy, the internal energy at constant volume, the entropy, and the volume of dissociation of tetramethylammonium iodide, tetraethylammonium iodide, and tetra-n-propylammonium iodide ion pairs in acetone solution. The sign and magnitude of these parameters over the range of conditions investigated, temperature 25 to 55 °C and atmospheric to 1.1 kbar pressure, indicated that the free ions in acetone solution are extensively solvated and that, depending on the conditions, solvent-shared or solvent-separated ion pairs are formed.

Tropolone-triethylamine equilibria in various solvents

1980 ◽  
Vol 33 (3) ◽  
pp. 491 ◽  
Author(s):  
B Poh ◽  
H Siow
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Dielectric Constant ◽  
Aprotic Solvent ◽  
Ion Pair ◽  
Pair Formation ◽  
Spectroscopic Methods ◽  
Aprotic Solvents ◽  
Ion Pair Formation ◽  
No Formation ◽  
Hydrogen Bonded

Infrared and nuclear magnetic resonance spectroscopic methods were used to study the tropolonetriethylamine equilibria. In aprotic solvents tropolone transfers its proton to triethylamine to form an ion pair which is in equilibrium with the intramolecularly hydrogen-bonded tropolone. The extent of ion pair formation increases with the dielectric constant of the aprotic solvent. Unlike the case of the p- nitrophenol-triethylamine system, there is no formation of a hydrogen bonded complex between tropolone and triethylamine. In the case of the tropolone-dibutylamine system in aprotic solvents, only ion pair formation is observed.

Electrical conductivities of quaternary ammonium salts in acetone.: Part I. Pressure and temperature effects

1968 ◽  
Vol 46 (12) ◽  
pp. 1977-1988 ◽  
Author(s):  
W. A. Adams ◽  
K. J. Laidler
Keyword(s):  
Concentration Dependence ◽  
Quaternary Ammonium ◽  
Temperature Effects ◽  
Dissociation Constants ◽  
Ion Pair ◽  
Quaternary Ammonium Salts ◽  
Ammonium Salts ◽  
Electrical Conductivities ◽  
Pressure And Temperature Effects ◽  
Tetraethylammonium Iodide

The equivalent conductivities of tetramethylammonium iodide, tetraethylammonium iodide, and tetra-n-propylammonium iodide in acetone solution were determined at concentrations from 1 to 10 × 10−4 mole/liter and at temperatures of 25 to 55 °C and pressures from atmospheric to 1.1 kbar. The concentration dependence of the equivalent conductivities was analyzed by the Shedlovsky method. Limiting equivalent conductivities and ion-pair dissociation constants are tabulated.

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