scholarly journals HYDROPHOBIC EFFECTS IN WATER AND WATER/UREA SOLUTIONS A COMPARISON

1994 ◽  
Vol 2 (2) ◽  
pp. 71-82
Author(s):  
E. A. Lissi ◽  
E. B. Abuin
Keyword(s):  
Aqueous Solution ◽  
Free Energy ◽  
Alkyl Chain ◽  
Standard Free Energy ◽  
The Other ◽  
Standard Entropy ◽  
Simple Description ◽  
Free Energy Of Transfer ◽  
Energy Of Transfer ◽  
Entropy Of Transfer

The partition of several n-alkanols, from methanol to n-nonanol, between n-hexane and water and between n-hexane and water containing 20 % (w/v) urea has been measured at temperatures ranging from 0 °C to 60 °C. The standard free energy of transfer from water to the urea-containing solution decreases with the length of the alkyl chain, being positive for the small alcohols and negative for the higher alkanols. The same tendency is observed upon all the temperature range considered. On the other hand, the standard entropy of transfer from water to the urea-containing solution increases with the length of the alkyl chain of the alkanol. These results are compatible with a simple description of the urea effect in terms of increasing the entropy of dissolution of the hydrophobic alkyl chain in the aqueous solution.

scholarly journals Potential drug delivery system: study of the association of a model nitroimidazole drug with aggregates of amphiphilic polymers on aqueous solution

2011 ◽  
Vol 47 (4) ◽  
pp. 725-731 ◽  
Author(s):  
Constain Hugo Salamanca Mejia ◽  
Bruno Felipe Urbano ◽  
Andres Floreal Olea Carrasco
Keyword(s):  
Aqueous Solution ◽  
Alkyl Chain ◽  
Standard Free Energy ◽  
System Study ◽  
Varying Length ◽  
Free Energy Of Transfer ◽  
Hydrophobic Microdomains ◽  
Polymeric Solutions ◽  
Model Drug ◽  
Energy Of Transfer

This study evaluated the association of N-hexyl-2-methyl-4-nitroimidazol, a model drug, to aggregates formed by anionic polyelectrolytes on aqueous solution. The alternating copolymers of maleic anhydride and N-vinyl-2-pyrrolidone were synthesized and then modified by reaction of the anhydride groups with aliphatic amines and alcohols of varying length of the alkyl chain. The partition of the model drug between water and the hydrophobic microdomains provided by the copolymers was studied using the pseudo-phase model to determinate the distribution coefficient K S, and the standard free energy of transfer ∆µ°t. The results indicate that all copolymers assessed are potential pharmaceutical reservoirs of the model drug. Nevertheless, the solubility of N-hexyl-2-methyl-4-nitroimidazol on the polymeric solutions is independent from the length of the alkyl chain of the copolymer.

Thermodynamics of transfer of Ph4C; scaled-particle theory and the Ph4As+/Ph4B− assumption for single ions

1979 ◽  
Vol 57 (15) ◽  
pp. 2004-2009 ◽  
Author(s):  
Michael H. Abraham ◽  
Asadollah Nasehzadeh
Keyword(s):  
Free Energy ◽  
Total Free Energy ◽  
Scaled Particle Theory ◽  
Free Energies ◽  
Particle Theory ◽  
Free Energy Of Transfer ◽  
Enthalpy And Entropy ◽  
Interaction Term ◽  
Energy Of Transfer ◽  
Entropy Of Transfer

Free energies of transfer of Ph4C from acetonitrile to 20 other solvents have been calculated from literature data. The contribution of the cavity term to the total free energy has been obtained from scaled-particle theory and Sinanoglu–Reisse–Moura Ramos theory. It is shown that there is little connection between the cavity term and the total free energy of transfer, and that there must be, in general, a large interaction term. If the latter is important for transfer of Ph4C, we argue that it must also be important for transfer of the ions Ph4As+ and Ph4B−. Previous suggestions that the interaction term is zero for transfer of these two ions are thus seen to be unreasonable. We also show, for six solvents, that the interaction term for Ph4C is very large in terms of enthalpy and entropy, and that scaled-particle theory seems not to apply to transfers of Ph4C between pure organic solvents.The free energy, enthalpy, and entropy of transfer of Ph4As+ = Ph4B− have been calculated by dividing the total transfer values into neutral and electrostatic contributions; reasonable agreement is obtained between calculated and observed values.

A vapor pressure method for the simultaneous determination of standard thermodynamic functions of both solutes in a ternary dilute solution

1978 ◽  
Vol 56 (6) ◽  
pp. 844-847 ◽  
Author(s):  
Claude Treiner ◽  
Pierre Tzias ◽  
Marius Chemla
Keyword(s):  
Aqueous Solution ◽  
Free Energy ◽  
Vapor Pressure ◽  
Tetrabutylammonium Bromide ◽  
Ternary Mixtures ◽  
Binary Solvents ◽  
Volatile Components ◽  
Polar Group ◽  
Free Energy Of Transfer ◽  
Energy Of Transfer

It is shown that from vapor pressure measurements on dilute solutions of ternary mixtures with one nonvolatile component, the standard free energy of transfer (ΔGt0) of both solutes from water to aqueous binary solvents can be determined simultaneously. The method is most useful in the case of volatile components. ΔGt0 values are discussed in particular in the case of the transfer of tetrahydrofuran, acetone, and acetonitrile from water to aqueous tetrabutylammonium bromide and urea solutions and compared to the case of the transfer of nonpolar solutes to the same aqueous solution. In each case, the free energy of transfer from water to an aqueous solution of a nonpolar molecule was negative, and introduction in that molecule of a polar group caused the free energy of transfer to be considerably less negative.

Impact of salts on the phase separation and thermodynamic properties of mixed nonionic surfactants in absence/attendance of polyvinyl alcohol

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Md Ackas Ali ◽  
Md. Ruhul Amin ◽  
Shamim Mahbub ◽  
Md. Delwar Hossen ◽  
Md. Anamul Hoque ◽  
...  
Keyword(s):  
Free Energy ◽  
Polyvinyl Alcohol ◽  
Aqueous Medium ◽  
Standard Free Energy ◽  
Tween 80 ◽  
Aqueous System ◽  
Standard Entropy ◽  
Thermodynamic Variables ◽  
Delta G ◽  
Energy Of Transfer

Abstract Mixed surfactant systems are used in different applied fields like pharmaceutical formulation rather than single surfactant. Therefore, the determination of the clouding nature of the triton X-100 (TX-100) + Tween 80 (TW-80) mixture was carried out in H2O and polyvinyl alcohol (PVA). In the occurrence of PVA, the cloud point (CP) values of TX-100 initially enhance with enhancing the concentration of PVA and tend to decrease after a certain concentration. For different ratios of TX-100 and TW-80 mixture having the same concentration of both solutions, CP values increase through the decreasing ratios of TX-100 with/without PVA. In the presence of polymer, at higher ratios of TX-100 than TW-80, the CP values are higher in magnitudes in comparison to the aqueous medium but at lower ratios of TX-100, the value of CP are lower in magnitudes in comparison to the aqueous system. The CP values of the TX-100 + TW-80 mixture in the salt system are lower in magnitudes than the aqueous medium in both the absence/presence of PVA. However, a reduction of CP values was obtained to a large extent for Na2SO4 over NaCl in the case of lower volume ratios of TX-100. Various thermodynamic variables (standard free energy ( Δ G c o ${\Delta}{G}_{c}^{o}$ ), standard enthalpy ( Δ H c o ${\Delta}{H}_{c}^{o}$ ), standard entropy ( Δ S c o ${\Delta}{S}_{c}^{o}$ ) change, thermodynamic parameters of transfer (free energy of transfer ( Δ G c , t o ${\Delta}{G}_{c,t}^{o}$ ), and transfer of enthalpies ( Δ H c , t o ${\Delta}{H}_{c,t}^{o}$ )) of phase transition) were also determined.

scholarly journals Standard Free Energy of Transfer of Potassium Chloride from Light to Heavy Water from Solubilities of Sparingly Soluble Salts.

1971 ◽  
Vol 25 ◽  
pp. 361-363 ◽  
Author(s):  
Pentti Salomaa ◽  
Marja Mattsén ◽  
Hans Sievertsson ◽  
Inger Skånberg ◽  
Karl-Gustav Svensson ◽  
...  
Keyword(s):  
Free Energy ◽  
Potassium Chloride ◽  
Heavy Water ◽  
Standard Free Energy ◽  
Soluble Salts ◽  
Free Energy Of Transfer ◽  
Energy Of Transfer

Thermodynamic Properties of Aqueous Organic Solutes in Relation to Their Structure. Part I. Free Energy of Transfer from H2O to D2O for a Series of Isomeric Ketones

1973 ◽  
Vol 51 (18) ◽  
pp. 3051-3061 ◽  
Author(s):  
Carmel Jolicoeur ◽  
Ghislain Lacroix
Keyword(s):  
Free Energy ◽  
Standard Free Energy ◽  
Scaled Particle Theory ◽  
Cavity Formation ◽  
Degree Of Branching ◽  
Structural Part ◽  
Hydrocarbon Chains ◽  
Free Energy Of Transfer ◽  
Energy Of Transfer ◽  
Heats Of Transfer

The solubilities of 18 decanones have been measured in H2O and D2O at 25 °C from their u.v. absorption spectra. The data were used to calculate ΔGt0, the standard free energy of transfer of these solutes from H2O to D2O ΔGt0 was found negative for the saturated ketones, but positive for most of the unsaturated and polycyclic isomers. A rough correlation was observed between ΔGt0 and the degree of branching in the hydrocarbon chains of the ketones: ΔGt0 increases with the degree of branching. From the temperature dependence of ΔGt0 obtained at 10, 25, and 40 °C, heats of transfer ΔHt0 were determined for typical ketones, namely 2-decanone and adamantanone. ΔHt0 was found as −2.1 kcal mol−1 for 2-decanone and ~0 ± 0.5 kcal mol−1 for adamantanone.The results are discussed in terms of two main contributions: (1) an isotope effect in the free energy of cavity formation and (2) perturbation of solvent structure by the solutes, differing in H2O and D2O. Using the scaled-particle theory to evaluate the former, the variations in the observed ΔGt0 are assigned to the structural part of ΔGt0.

Use of the scaled-particle theory for the determination of single ion standard free energy of transfer between solvents

1977 ◽  
Vol 55 (4) ◽  
pp. 682-685 ◽  
Author(s):  
Claude Treiner
Keyword(s):  
Free Energy ◽  
Mixed Solvents ◽  
Standard Free Energy ◽  
General Rule ◽  
Scaled Particle Theory ◽  
Particle Theory ◽  
Solvent Interactions ◽  
Free Energy Of Transfer ◽  
Energy Of Transfer

The tetraphenylboron extrathermodynamic assumption is one of the methods most often used for the evaluation of single ion standard thermodynamic functions of transfer between two solvents. We show in this article that the scaled-particle theory may be useful for discriminating among those solvents for which this extrathermodynamic assumption may be questionable because of strong solute–solvent interactions. Although no general rule is proposed, the tetraphenylboron assumption seems valid in the case of the free energy of transfer between water and solvents like methanol, ethanol, acetonitrile, and formamide; it should not be used in the case of the transfer to solvents like propylene carbonate, dimethylsulfoxide or sulfolane. The scaled-particle theory may also be used to predict within 20% the standard free energy of transfer of the tetraphenylboron ion between water and aqueous mixed solvents; examples are given for water–methanol and water–ethanol mixtures.

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