Studies of partial molar volumes of alkylamine in non-electrolyte solvents II. Alkyl amines in chloroalkanes at 303.15 and 313.15 K

Oswal, S.L.; Desai, J.S.; Ijardar, Sushma P.; Jain, Deepak M.

doi:10.1016/j.molliq.2008.07.016

Cited by 28 publications

(21 citation statements)

References 57 publications

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“…However, without explicitly including a third box to represent the low-density CH 3 endgroups of the interfacial monolayer, this model is unphysical. The low-density layer is expected because of the (up to twofold) larger volume of the solvated CH 3 moiety as compared to that of CH 2 one (25,26). Such low-density layers were demonstrated to be essential to obtain physically acceptable models for interfaces between a solid layer of alkyl chains and a liquid alkyl bulk (24,27).…”

Section: Resultsmentioning

confidence: 99%

Modification of deeply buried hydrophobic interfaces by ionic surfactants

Tamam

Pontoni

Sapir

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

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Hydrophobicity, the spontaneous segregation of oil and water, can be modified by surfactants. The way this modification occurs is studied at the oil-water interface for a range of alkanes and two ionic surfactants. A liquid interfacial monolayer, consisting of a mixture of alkane molecules and surfactant tails, is found. Upon cooling, it freezes at T s , well above the alkane's bulk freezing temperature, T b . The monolayer's phase diagram, derived by surface tensiometry, is accounted for by a mixtures-based theory. The monolayer's structure is measured by high-energy X-ray reflectivity above and below T s . A solid-solid transition in the frozen monolayer, occurring approximately 3°C below T s , is discovered and tentatively suggested to be a rotator-to-crystal transition.H ydrophobicity (1) is abundant in nature and in technology (2). It plays a dominant role in fields ranging from the structure of living matter, like cell membrane stabilization and protein folding, to microemulsion-mediated nanoparticle and quantum dot formation (1,(3)(4)(5)(6)(7). Although the macroscopic phenomenology of hydrophobicity is well studied, its theoretical understanding, particularly on a molecular level, is still incomplete (1,8). Recent progress in X-ray scattering from buried interfaces allowed determination of the structure of hydrophobic interfaces (including the oil-water one) with near-atomic resolution, leading to an animated debate on the molecular-scale origin and manifestations of the hydrophobic interaction (9-13). Surfactants are often used to modify the hydrophobic interactions in a manner that reduces the interfacial free energy. However, the microscopic structure of surfactant-modified bulk oil-water interfaces, the subject of the present study, has been studied by X-ray methods only for nonionic alkanol surfactants (14, 15). X-ray measurements for oil-water interfaces modified by ionic surfactants are not available in the literature. Macroscopic optical measurements have uncovered intriguing interface structure modifications (16), indicating that these more widely used and more complex electrically charged surfactants, which also have bulkier headgroups, may modify the interface differently from the nonionic ones. Thus, a key ingredient in the fundamental understanding of the relation between ionic surfactants and the hydrophobic interaction is still missing.Using X-ray reflectivity (XR) and surface tensiometry, we measured the atomic-resolution structure and thermodynamics of oil-water interfaces decorated by ionic surfactants (see Fig. 1A). Two different interfacial phases are observed. At high temperatures, a liquid interfacial monolayer is found; upon cooling, a frozen monolayer forms at the interface, separating the bulk liquid oil and aqueous phases. We measured the interfacial phase diagram and offer a simple thermodynamic model which fully accounts for the interfacial freezing (IF). At a lower temperature, the frozen monolayer is found to undergo an additional transition to full crystallinity where the m...

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Section: Resultsmentioning

confidence: 99%

Modification of deeply buried hydrophobic interfaces by ionic surfactants

Tamam

Pontoni

Sapir

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

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“…In this work simple and cheap methods for analysis can be used. The apparent molar volumes V φ [13][14][15] were calculated using equation (3) The values of V φ for phenylalanine in various solvents at 298.15 K are presented in Table (2).…”

Section: Resultsmentioning

confidence: 99%

Molal Solubility, Dissociation, Association and Solvation Parameters for Saturated Phenylalanine Solutions in Various Solvents at 298.15 K

Gomaa¹

2012

AJB

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The molal solubilities for saturated solutions of phenylalanine at 298.15 K in various solvents were determined.The solvents used are, water (W), ethanol (Et), dimethylsulphoxide (DMSO), acetonitrile (AN), methanol (Me), acetone (Ac), 1-4, dioxane (Di) and N, N-dimethylformamide (DMF).From the experimental data for solubilities, pH and densities, the different volumes, molar: electrostriction and Van der Waals and apparent molar volumes were estimated. The free energies of dissociation (∆G d ), free energies of association (∆G A ), difference free energies (∆∆G) and free energies of solvation (∆G s ) for phenylalanine saturated solutions in various solvents were also calculated. The solvation numbers were also estimated. It was concluded that the solute-solvent interaction increased by increasing the solvation free energies due mainly to the greater of the association parameters in the organic solvents.

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“…The apparent molar volumes V φ [14,15] were calculated using equation 3 The values of V φ for O-chlorobenzoic acid in various solvents at 298.15 K are presented in Table (2). The activity coefficient was calculated by using the relation log γ ± = -0.5062 m [17].…”

Section: Resultsmentioning

confidence: 99%

Molal Solubility, Dissociation, Association and Solvation Parameters for Saturated O -Chlorobenzoic Acid Solutions in Various Solvents at 298.15 K

Gomaa¹

2012

FPH

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The molal solubility for saturated solutions of O-chlorobenzoic acid at 298.15 K in various solvents was determined. The solvents used are, water (W), ethanol (Et), dimethylsulphoxide (DMSO), acetonitrile (AN), methanol (Me), 1-4, dioxane (Di) and N , N-dimethylformamide (DMF). From the experimental data for solubility, pH , densities, the different volumes, free energies, dissociation constants, association constants and solvation parameters were estimated. Also the free energies of dissociation and association were also evaluated. Other solvation parameters like the solvation numbers were cited here to help explaining the solubility trend.This work give a lot of data for the solubility of orthochlorobenzoic acid which help the biologist for using it as food preserver .The results were also discussed.

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Studies of partial molar volumes of alkylamine in non-electrolyte solvents II. Alkyl amines in chloroalkanes at 303.15 and 313.15 K

Cited by 28 publications

References 57 publications

Modification of deeply buried hydrophobic interfaces by ionic surfactants

Modification of deeply buried hydrophobic interfaces by ionic surfactants

Molal Solubility, Dissociation, Association and Solvation Parameters for Saturated Phenylalanine Solutions in Various Solvents at 298.15 K

Molal Solubility, Dissociation, Association and Solvation Parameters for Saturated O -Chlorobenzoic Acid Solutions in Various Solvents at 298.15 K

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