Influence of the structure of amphiphilic anions on the Krafft temperature of micellar solutions of anionic surfactants

The influence of the structure of surfactants on the Krafft temperature T _k was studied for aqueous solutions of anionic surfactants containing the sulfate and sulfonate head groups, the hydrophilic (H) and lipophilic (L) fragments in amphiphilic anions, and various polar and C₈—C₁₈ hydrocarbon groups. The best statistical quality was obtained for the model with separate account of the effect of the H and L structural fragments on the T _k value.     

Ultrasonic absorption in aqueous salts of the lanthanides. IV. Sulfates in D2O

The rates of formation of the monosulfate complexes of the trivalent rare earth ions of Pr, Sm, Gd, and Dy have been measured at 25°C in D₂O and additional measurements made on Pr, Sm, Gd, Tb, and Ho in water. Using formation constants recently calculated from conductance measurements in D₂O, the rate data were compared to our reevaluated data in water to establish if a solvent isotope effect was present, which may contribute to our understanding of the mechanism of complexation. Contrary to previous reports, none is observed, the rate constants being in agreement within experimental error and within the limits of the assumptions used in the mathematical interpretation. Evidence therefore points to a dissociative mechanism in which the rate of exchange of the solvent from the primary hydration sphere of the cation is rate-determining.     

Determination of fatty alcohol ethoxylates and alkylether sulfates by anionic exchange separation, derivatization with a cyclic anhydride and liquid chromatography

A method for the separation, characterization and determination of fatty alcohol ethoxylates (FAE) and alkylether sulfates (AES) in industrial and environmental samples is described. Separation of the two surfactant classes was achieved in a 50:50 methanol-water medium by retaining AES on a strong anionic exchanger (SAX) whereas most FAE were eluted. After washing the SAX cartridges to remove cations, the residual hydrophobic FAE were eluted by increasing methanol to 80%. Finally, AES were eluted using 80:20 and 95:5 methanol-concentrated aqueous HCl mixtures. Methanol and water were removed from the FAE and AES fractions, and the residues were dissolved in 1,4-dioxane. In this medium, esterification of FAE and transesterification of AES with a cyclic anhydride was performed. Phthalic and diphenic anhydrides were used to derivatizate the surfactants in industrial samples and seawater extracts, respectively. Separation of the derivatized oligomers was achieved by gradient elution on a C8 column with acetonitrile/water in the presence of 0.1% acetic acid. Good resolution between both the hydrocarbon series and the successive oligomers within the series was achieved. Cross-contamination of FAE with AES and vice versa was not observed. Using dodecyl alcohol as calibration standard, and correction of the peak areas of the derivatized oligomers by their respective UV-vis response factors, both FAE and AES were evaluated. After solid-phase extraction on C18, the proposed method was successfully applied to the characterization and determination of the two surfactant classes in industrial samples and in seawater.     

Thermodynamics of aqueous solutions of the alkali metal sulfates

The available thermodynamic properties for aqueous solutions of each of the alkali metal sulfates have been combined and analyzed within the framework of the ion interaction model at temperatures up to 225°C. It was necessary to set ₁ equal to 1.4kg^1/2-mol^–1/2 in order to obtain a satisfactory fit. The temperature dependence of the ion interaction parameters was given the functional form used by Rogers and Pitzer⁽¹⁾ in their study of Na₂SO₄(aq). With few exceptions, it was possible to reproduce the available thermodynamic data for aqueous solutions of the alkali metal to within the estimated experimental error. Thermodynamic results for Na₂SO₄(aq) appear to be adequate in this temperature range, but enthalpy and heat capacity data for the other alkali metal sulfate solutions are conspicuously lacking. Activity coefficients of these electrolytes decreased to less than 0.1 at moderate molalities at the higher temperatures, and their order changed with increasing temperature; two results which could be due to a combination of hydration and association effects.Research sponsored by the Division of Chemical Sciences, Office of Basic Energy Sciences of the U.S. Department of Energy under contract DE-AC05-840R21400 with the Martin Marietta Energy Systems, Inc.     

Liquid crystals formed in sodium alkyl sulfates-water systems studied by positron annihilation techniques

Lyotrophic phase transitions were investigated in liquid crystalline systems of sodium alkyl sulfate-water. The positron annihilation parameters indicated the presence of a nematic phase in sodium dodecyl sulfate water-system in absence of additives. The effect of the hydrocarbon chain-length and unsaturation of the surfactant on the nematic phase formation were also studied. Liquid crystals of sodium 10-undecenoate were polymerized by ultraviolet irradiation. Polymerization is seen to cause a gradual change from the hexagonal to the lamellae phase.This research is in furtherance of the USA-Mexico Cooperative Science Program through the National Science Foundation and the Consejo Nacional de Ciencia y Tecnología     

Thermal decomposition of double rare earth(III) monomethylammonium sulfates with general empirical formula CH3NH3Ln(SO4)2·3H2O (Ln=La-Er and Y)

Double rare earth(III) monomethylammonium sulfates with general empirical formula CH₃NH₃Ln(SO₄)₂·3H₂O (Ln = La-Er and Y) were synthesized and examined by X-ray powder diffraction, TG, DTG and DTA in the temperature range from 25° to 700°C, and chemical analysis. It was found that these compounds are isomorphous and decompose to rare earth sulfate at 700°C.The authors are grateful to the Research Council of Slovenia for financial support of this research.     

Asymmetric synthesis of aryloxypropanolamines via OsO4-catalyzed asymmetric dihydroxylation

A simple and effective procedure for the enantioselective synthesis of several β-adrenergic blocking agents incorporating the first asymmetric synthesis of celiprolol, is described. The key steps are (i) sharpless asymmetric dihydroxylation of aryl allyl ethers to introduce chirality into the molecules and (ii) conversion of cyclic sulfates into the corresponding epoxides using a three-step procedure.     

Metal Hydrogen Sulfates M(HSO4)n: As Efficient Catalysts for the Synthesis of Quinoxalines in EtOH at Room Temperature

A convenient method for the synthesis of quinoxalines catalysed by metal hydrogen sulfates by the reaction of 1,2‐diamino compounds and 1,2‐dicarbonyl compounds in ethanol as solvent at room temperature is reported.     

One-pot, efficient, and regioselective syntheses of 1,4-disubstituted 1,2,3-triazoles using aryldiazonium silica sulfates in water

A one-pot, efficient, and straightforward procedure for the copper-catalyzed synthesis of 1,4-disubstituted 1,2,3-triazoles is studied by in situ generation of aryl azides via the reaction of aryldiazonium silica sulfates and sodium azide, followed by coupling with a terminal alkyne. These reactions are carried out in water at room temperature without using any additional ligands.