The Hydrophobic Propensity of Water toward Amphiprotic Solutes: Predicton and Molecular Origin of the Aqueous Solubility of Aliphatic Alcohols

Ruelle, Paul; Kesselring, Ulrich W.

doi:10.1021/js9603109

Cited by 22 publications

(15 citation statements)

References 48 publications

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“…A double positive influence on the aqueous solubility of alcohols is provided by the formation of mixed water–alcohol hydrogen-bond chains by the insertion of the hydroxyl groups into water: the alcohol molecules are stabilized in the hydrogen-bond chains, and the hydrophobic effect of water is reduced. Each of these influences alters the Gibbs free energy of the system differently …”

Section: Introductionmentioning

confidence: 99%

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Solvent Synergists for Improved Kinetic Hydrate Inhibitor Performance of Poly(N-vinylcaprolactam)

2020

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The synergetic effect of a range of different solvents on the kinetic hydrate inhibitor (KHI) performance of poly(N-vinylcaprolactam) (PVCap) has been investigated. The equipment used was a high-pressure (76 bar) rocking cell apparatus using slow constant cooling (approximately 1 °C/h from 20.5 °C) and a synthetic natural gas mixture forming structure II hydrate. The synergetic effect was investigated by adding 5000 ppm of a range of alcohols, glycol ethers, and ketones to a solution of 2500 ppm of PVCap (M w = 10 000 g/mol). For many of the additives, the ranking of the synergetic effect can be explained with reference to the size, shape, and hydrophobicity of the main alkyl group (“tail”) in the molecule as well as the presence of a glycol ether group. Among all of the solvents investigated, the best synergetic effect was achieved by 4-methyl-1-pentanol. When 5000 ppm of 4-methyl-1-pentanol was added to 2500 ppm of PVCap, no hydrate formation occurred down to the minimum test temperature of 3 °C (subcooling at ca. 16.3 °C) in 15 parallel experiments compared to 10.4 °C for pure PVCap. Predictions for improved glycol ether synergists are given.

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Section: Introductionmentioning

confidence: 99%

“…Each of these influences alters the Gibbs free energy of the system differently. 38 The mechanism behind the synergetic effect of alcohols on KHI polymers is not fully understood. One reported hypothesis is that alcohols increase the ability of the KHI polymers to adsorb on nucleation and/or growth sites.…”

Section: Introductionmentioning

confidence: 99%

Solvent Synergists for Improved Kinetic Hydrate Inhibitor Performance of Poly(N-vinylcaprolactam)

2020

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“…Considering the various enthalpy and entropy changes involved in the whole solubility process, a number of thermodynamic expressions [5][6][7][8] have been developed to account for the effects of the various interactions between molecules in solution on the chemical potential of the solute. Depending on the functional groups present on the solute and solvent molecules, different contributions may be considered: (1) the fluidization of the solute or its ideal solubility (A term), (2) the combinatorial entropy originating from the exchange possibilities between the solute and solvent molecules in solution (B term); (3) the mobile order entropy decrease (solvophobic effect) of the self-associated solvent molecules following the dissolution of the solute substance (F term); (4) the change in the nonspecific forces upon mixing (D term); (5) the effect of the H-bonds between the proton-acceptor sites of the solute and the protondonor solvents (O term); and (6) the effect of the H-bonds formed by the amphiphilic groups of the solute including its self-association in solution (OH term).…”

Section: The Universal Solubility Equationmentioning

confidence: 99%

“…6,8 In eqs 6 and 7, K Oi and K OHi are the stability constants governing the solute-solvent group interactions of type i whose number are, respectively, ν Oi and ν OHi . Although the numbers of identical and independent interaction sites are important in the solubility prediction, their counting is in most cases not very difficult.…”

Section: The Universal Solubility Equationmentioning

confidence: 99%

The Hydrophobic Effect. 2. Relative Importance of the Hydrophobic Effect on the Solubility of Hydrophobes and Pharmaceuticals in H-Bonded Solvents

Ruelle¹,

Kesselring²

1998

Journal of Pharmaceutical Sciences

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The quantitative development of the nonergodic mobile order thermodynamics involving the new interpretation of the hydrophobic effect leads to a general solubility equation. This equation is applied to predict the aqueous and alcohol solubility of chemicals ranging from nonpolar or slightly polar with no H-bonding capacity to polyfunctional polar compounds including pharmaceuticals. The analysis of the relative importance of the contributions involved in the solubility model [i.e., the fluidization of the solute (for solids), the correction for the mixing entropy, the change of the nonspecific cohesion forces, and the formation of solvent-solvent (hydrophobic effect), solute-solute, and solute-solvent H-bonds] unambiguously demonstrates that the hydrophobic effect is essential for predicting the aqueous or alcohol solubility of any substance in general, and of nonpolar compounds in particular. The difference between the origin of the solubility of hydrocarbons in water and of water in hydrocarbons is furthermore presented. In both cases, the quasilinear solubility dependence on the molar volume of the hydrocarbon is of an entropic nature.

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“…The constant K BB stands for the stability constant ruling the solute self-association in solution; and b is a constant accounting for the primary (1.2), secondary (2.0), or tertiary (2.9) nature of the proton-donor group in the case this group is a hydroxyl group and the solubility is estimated in water. 12,13 The F contribution corresponds to the hydrophobic effect, the meaning and the expression of which are directly derived from the quantitative thermodynamic treatment of the mobile order theory that prevails in H-bonded liquids. 6 In particular, this treatment takes into account both the nonergodicity and the mobility of the H-bonds in liquids.…”

Section: The Partition Coefficient and Mobile Order Thermodynamicsmentioning

confidence: 99%

The Hydrophobic Effect. 3. A Key Ingredient in Predicting n-Octanol–Water Partition Coefficients

Ruelle¹,

Kesselring²

1998

Journal of Pharmaceutical Sciences

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The quantitative development of the mobile order theory in H-bonded liquids is extended to predict the n-octanol/water partition coefficient (P). The log P predictive equation strictly issued from a thermodynamic treatment reduces to a simple linear volume-log P relationship whose intercept and slope encode, respectively, the solvation and entropy effects. For noncomplexing substances, the partition coefficient values result from two volume-dependent entropic contributions reflecting (a) the difference in the exchange entropy between the solute and solvent molecules in the n-octanol and water phases, and (b) the propensity difference between the two H-bonded solvents to induce a hydrophobic effect toward the solute. Although both effects increase, although with opposite signs, compared with the growing molar volume of the partitioned compound, the hydrophobic contribution always predominates favoring the transfer of the solute into the organic phase and hence increasing its partition coefficient. When dealing with complexing chemicals, the hydrophobic effect-related term, though remaining the dominant factor in most cases, is more or less counterbalanced by the formation of H-bonds between the interacting sites of the solute and the n-octanol and water solvent molecules. The log P, corrected for the substantial content of water into n-octanol, is estimated for a number of compounds of environmental and pharmaceutical interest. The extent to which the entropic and enthalpic factors affect the overall partition coefficient value is analyzed.

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The Hydrophobic Propensity of Water toward Amphiprotic Solutes: Predicton and Molecular Origin of the Aqueous Solubility of Aliphatic Alcohols

Cited by 22 publications

References 48 publications

Solvent Synergists for Improved Kinetic Hydrate Inhibitor Performance of Poly(N-vinylcaprolactam)

Solvent Synergists for Improved Kinetic Hydrate Inhibitor Performance of Poly(N-vinylcaprolactam)

The Hydrophobic Effect. 2. Relative Importance of the Hydrophobic Effect on the Solubility of Hydrophobes and Pharmaceuticals in H-Bonded Solvents

The Hydrophobic Effect. 3. A Key Ingredient in Predicting n-Octanol–Water Partition Coefficients

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