Water In Non-polar Solvents Research Articles

Experimental and simulation study of reverse micelles formed by aerosol-OT and water in non-polar solvents.

The formation of reverse micelles by aerosol-OT [sodium bis(2-ethylhexyl) sulfosuccinate] in hydrocarbon solvents, and in the presence of water, is studied using a combination of atomistic molecular-dynamics simulations and small-angle neutron scattering (SANS). There have been many previous studies of aerosol-OT and its self-assembly in both water and non-aqueous solvents, but this work is focused on a combined experimental and simulation study of reverse-micelle formation. The effects of hydration (with water-to-surfactant molar ratios in the range 0-60) and solvent (cyclohexane and n-dodecane) are investigated. A force field is adapted that results in spontaneous formation of reverse micelles starting from completely randomized configurations. The computed dimensions of the reverse micelles compare very favourably with those determined in SANS experiments, providing validation of the simulation model. The kinetics of reverse-micelle formation are studied with a 50-ns, 1.7-million-atom system which contains, in the steady state, about 50 reverse micelles. The internal structures of reverse micelles are characterized with mass density profiles, and the effects of solvent, and the structural crossover from highly structured water to 'bulk' water in the core, are detailed. The corresponding changes in the molecular reorientation times of sequestered water are also determined. Overall, the combination of experiment and simulation gives a detailed picture of reverse-micelle self-assembly and structure.

Isolating the non-polar contributions to the intermolecular potential for water-alkane interactions.

Intermolecular potential models for water and alkanes describe pure component properties fairly well, but fail to reproduce properties of water-alkane mixtures. Understanding interactions between water and non-polar molecules like alkanes is important not only for the hydrocarbon industry but has implications to biological processes as well. Although non-polar solutes in water have been widely studied, much less work has focused on water in non-polar solvents. In this study we calculate the solubility of water in different alkanes (methane to dodecane) at ambient conditions where the water content in alkanes is very low so that the non-polar water-alkane interactions determine solubility. Only the alkane-rich phase is simulated since the fugacity of water in the water rich phase is calculated from an accurate equation of state. Using the SPC/E model for water and TraPPE model for alkanes along with Lorentz-Berthelot mixing rules for the cross parameters produces a water solubility that is an order of magnitude lower than the experimental value. It is found that an effective water Lennard-Jones energy ε(W)/k = 220 K is required to match the experimental water solubility in TraPPE alkanes. This number is much higher than used in most simulation water models (SPC/E-ε(W)/k = 78.2 K). It is surprising that the interaction energy obtained here is also higher than the water-alkane interaction energy predicted by studies on solubility of alkanes in water. The reason for this high water-alkane interaction energy is not completely understood. Some factors that might contribute to the large interaction energy, such as polarizability of alkanes, octupole moment of methane, and clustering of water at low concentrations in alkanes, are examined. It is found that, though important, these factors do not completely explain the anomalously strong attraction between alkanes and water observed experimentally.

Fragmentation of Amino Ketones by Photoinduced Electron Transfer

Abstract Irradiation of electron acceptors such as 9,10-dicyanoanthracene (DCA) in the presence of the amino ketone 3-methyl-3-(4-morpholinyl)-2-butanone and water in nonpolar solvents leads to an oxidative cleavage of the amino ketone to form ultimately 4-acetylmorpholine and acetone together with 9,10-dihydro-9,10-dicyanoanthracene. A mechanism can be developed whereby single-electron transfer quenching of the excited DCA is followed by a nucleophilic attack on the acyl carbon of the cation radical; an intermediate acyl-DCA adduct has been detected and its thermal decomposition to the final products observed. The net result is an unprecedented ketone to amide interconversion in which a strong carbon-carbon bond in the donor is selectively cleaved. Related reactions are observed with other acceptors (thioindigo) and other amino ketones.

Water in nonaqueous solvents

Abstract

Determination of traces of water in a solvent. II. Application to hydration of 3,4-xylenol in wet benzene

The study of vapor pressure differences between wet benzene and the solutions of 3,4-xylenol in benzene as a function of the vapor phase volume provides evidence for the hydration of xylenol by water dissolved in benzene. The mode of association of 3,4-xylenol in benzene is ascertained and association and hydration constants are estimated. The hydration constant is four times larger than the association constant. Association equilibria are highly perturbed by traces of water in non-polar solvents.

Determination of traces of water in a solvent. I. Method using vapor pressure differences

The difference (Δ p) between the vapor pressure of a solvent containing traces of water and that of the dry solvent as a function of the ratio of vapor and liquid volumes ( V g/ V l) has been measured and it has been shown that 1/Δ p is a linear function of V g/ V l. From the slope of the straight line, the solubility of water in the solvent can be determined. A method for the determination of traces of water in non-polar solvents has been proposed.

Relationships among Melting Point of Cationic Surfactants, Their Solubility Behavior, Micelle Formation and Solubilization of Water in Nonpolar Solvents

カチオン活性剤の融点,その無極性溶媒中での溶解性,ミセル形成および水の可湾化の間の関連性を調べるために,臭化およびヨウ化ジアルキルジメチルアンモニウム,脂肪酸アルキルアンモニウムを合成し,これらのカチオン活性剤の融点およびベンゼン,シクロヘキサン中での溶解温度,ミセル童,水の可溶化量を測定した。一般に融点は,臭化塩>ヨウ化塩>脂肪酸塩の順に上昇したが溶解温度の低下度は融点の順とは逆であった。しかしながら,融点および溶解温度の活性剤の炭化水素基鎖長による変化は同様であった。ミセルの会合数の大きさは,臭化塩>ヨウ化塩>脂肪酸塩の順となり,この順序は,融点および水の可溶化の大きさの順と一致した。そして,これらの物理化学的性質の間の関連性を活性剤の極性基の溶媒和およびイオン性の違いによって説明した。

Solubilization of water in non-polar solvents by detergent mixtures

Solubilization of water in non-polar solvents by detergent mixtures

Solubilization of water in non-polar solvents by cationic detergents

Solubilization of water in common organic solvents by fatty acid salts of long-chain (C 12 —C 18 ) aliphatic primary amines was studied. It was found that, of all the salts from formate to palmitate and oleate, dodecylamine- n -butyrate and octadecylamine propionate solubilize most in xylene, the figure reaching about 29 molecules of H 2 O /mole of soap. Additions of free amine enhanced solubilization, while free butyric acid decreased the intake. Our viscosity and freezing-point measurements of the same systems indicated that the additive is most likely to form a complex with soap micelles, and that their solubilizing power is modified thereby. Freezing-point measurements of detergent solutions with and without the solubilized phase showed, surprisingly enough, that the dissolved water elevates the freezing-points considerably, showing that solubilized water acts as a binding agent between micelles and probably promotes micelle formation. The results are discussed and correlated on Winsor’s theory of solubilization.