Study on the Interfacial Tensions Between Oils and Alkylbenzene Sulfonate Gemini Surfactant Solutions

Interfacial tensions (IFT) of five alkylbenzene sulfonate Gemini surfactants Ia, Ib, Ic, Id, and Ie at different oils/water systems were measured by a spinning drop interfacial tensiometer. And critical micelle concentration (CMC), the interfacial tension at CMC (γ_CMC), maximum interfacial excess concentration (Γ _max) and the surface area per molecule (A_min) were calculated. The results indicated that the CMC values determined with interfacial tension method were lower than those determined with surface tension method. And γ_CMC for Ie is larger than that for Ia, Ib, Ic, and Id. In addition, the effects of temperature and hydrophobic chains on dynamic IFT were also studied. With the increment of temperature, dynamic IFT is easier to reach a stable value. However, with the increment of hydrophobic chains, dynamic IFT is more difficult to reach a stable value. Each Gemini surfactant produces a minimum IFT when measured against a different n-alkane.     

Synthesis and Performance of Novel Sulfonate Gemini Surfactant with Trialkyl Chains

A new type of sulfonate gemini surfactant with three lipophilic alkyl chains (3C₁₀-DS) was synthesized, and the structure of the product was confirmed by using the infrared spectrum and mass spectrum. Its critical micelle concentration (CMC) is 0.41 mmol/L, one order of magnitude lower than those of convectional (single-chain) surfactants, and the minimum surface tension is 27.6 mN/m. The interfacial tension (IFT) between the compound system of 3C₁₀-DS and petroleum sulfonate (PS) and the simulated oil reaches ultra-low levels (10^?3 mN/m), and there exists significant synergistic effect between 3C₁₀-DS and PS. The compound flooding system consisting of polymer and the mixture of 3C₁₀-DS and PS can effectively improve oil recovery for high-medium permeability cores and have a good application prospect in enhancing oil recovery.     

Isolation and Characterization of Naphthenic Acids from a Metal Naphthenate Deposit: Molecular Properties at Oil‐Water and Air‐Water Interfaces

Naphthenic acids from a West African metal naphthenate deposit have been isolated and characterized by infrared (IR), nuclear magnetic resonance (NMR), and Fourier transform ion cyclotron resonance mass spectrometry (FT‐ICR MS). The sample has been shown to comprise a narrow group of 4‐protic naphthenic acids of molecular weight ～1230 Da. The determined mass of 1230.0627 Da suggests a compound with the elemental composition C₈₀H₁₄₂O₈. The NMR data show no sign of carbon‐carbon multiple bonds. Hence, the elemental composition indicates the presence of six saturated hydrocarbon rings. The naphthenic acids have proved to be highly oil‐water (o/w) interfacially active. On elevation of the pH from 5.6 to 9.0, interfacial activity increases gradually due to a higher degree of dissociation of the carboxylic groups. At pH 9.0, the interfacial tension (IFT) between water and toluene‐hexadecane (1–9 vol.) is lowered by ～40 mN/m at concentrations of only 0.0050–0.010 mM naphthenic acid. The time rate of decrease of the IFT (dγ/dt) is also concentration‐dependent, and a well‐defined IFT is attained at long observation periods.

The C₈₀ naphthenic acids form relatively unstable Langmuir monolayers. The stability decreases further with increasing pH as more monomers become dissociated and dissolve into the aqueous phase. The stability is altered upon addition of calcium ions into the subphase due to formation of calcium naphthenate at the surface. In the undissociated state, the acids have a molecular area of ～160 Å²/molecule in the noninteracting region. The high area reflects an extended molecular structure comprising four carboxylic head groups, which are likely to be separated by hydrocarbon chains.     

Model compounds for C80 isoprenoid tetraacids: Part II. Interfacial reactions, physicochemical properties and comparison with indigenous tetraacids

Novel model compounds are desired to study properties of a narrow group of tetrameric acids from crude oil mainly responsible for naphthenate deposition. It is important to make a comparison to find to what degree the model compounds can reflect the properties of the indigenous tetraacids and where there are deviations, before using the model compounds in naphthenate research. A comparison between two synthesised model compounds and indigenous tetraacids has been carried out regarding physicochemical properties including thermal solid state properties, critical micelle concentrations, monolayer properties and interfacial reactions. Of the two studied model compounds, one was observed to form the same cross-linked network with Ca²⁺, a typical feature of the indigenous tetraacids. Interfacial reactions using the pendant drop technique also showed that four different divalent cations could all form this network with the model tetraacid. The film formation was however dependent on the ratio M²⁺/TA. The main deviations were in the solid state, where the model compounds showed crystalline transitions, contrary to the indigenous tetraacids. We conclude that the two different model compounds mimic the indigenous tetraacids well with respect to several of their properties and are suitable for use in naphthenate research.     

Fe-Mediated S–S Bond Cleavage and Its Application in the Synthesis of α-Arylthio Carbonyl Compounds

In the presence of iron dust, diaryl disulfides react with α-bromo carbonyl compounds to obtain α-arylthio carbonyl compounds in good yield at 90 °C under an N₂ atmosphere, using commercial dimethylformamide (DMF) as solvent. The possible reaction mechanism is that the disulfide is reduced by iron dust to give ArSFeSAr and then reacted with α-bromo carbonyl compounds to give product α-arylthio carbonyl compounds and FeBr₂.     

Synthesis and properties of nonylphenol-substituted dodecyl sulfonate

Nonylphenol-substituted dodecyl sulfonate (C₁₂-NPAS) was synthesized via sulfonation-alkylation-neutralization using 1-dodecene, SO₃, and nonylphenol as raw materials. The properties such as surface tension, interfacial tension (IFT), wettability, foam properties, and salinity tolerance of C₁₂-NPAS were systematically investigated. The results show that the critical micelle concentration (CMC) of C₁₂-NPAS was 0.22?mmol?·?L^?1 and the surface tension at the CMC (γ_CMC) of C₁₂-NPAS was 29.4 mN/m. When compared with the traditional surfactants sodium dodecyl benzene sulfonate (SDBS), sodium dodecyl sulfate (SDS), and linear alkylbenzene sulfonate (LAS), the surface properties of C₁₂-NPAS were found to be superior. The IFT between Daqing crude oil and a weak-base alkaline/surfactant/polymer (ASP) oil flooding system containing 0.1?wt% of C₁₂-NPAS can reach an ultralow level of 2.79?×?10^?3 mN/m, which was lower than that found for the traditional surfactant heavy alkylbenzene sulfonate (HABS). The salinity and hardness tolerance of C₁₂-NPAS were much stronger than those found for conventional surfactants, petroleum sulfonate, and LAS. C₁₂-NPAS also shows improved wetting performance, foamability, and foam stability.     

Evaluation of Monolithic Columns for Determination of Formaldehyde and Acetaldehyde in Sugar Cane Spirits by High-Performance Liquid Chromatography

Abstract

High-Performance Liquid Chromatography (HPLC) conditions are described for separation of 2,4-dinitrophenylhydrazone (2,4-DNPH) derivatives of carbonyl compounds in a 10 cm long C₁₈ reversed phase monolithic column. Using a linear gradient from 40 to 77% acetonitrile (acetonitrile-water system), the separation was achieved in about 10 min—a time significantly shorter than that obtained with a packed particles column. The method was applied for determination of formaldehyde and acetaldehyde in Brazilian sugar cane spirits. The linear dynamic range was between 30 and 600 µg L^?1, and the detection limits were 8 and 4 µg L^?1 for formaldehyde and acetaldehyde, respectively.     

THE SURFACE,INTERFACIAL AND ELECTROKINETIC PROPERTIES OF BIOMINERALS

ABSTRACT

The apolar (Lifshitz van der Waals) component (γ ^LW _S) and the polar [electron-acceptor (γ ⁺ _S) and electron-donor (γ ^? _S)] parameters of the surface tension of biominerals and surfaces of dental hard tissues have been measured, as well as their ζpotentials. The interfacial tensions between their surfaces and aqueous solutions, determined using van Oss-Chaudhury-Good equations, are comparable with the interfacial free energy values obtained from the kinetics of crystallization and dissolution using a constant composition technique. The electron-donor (γ ^? _S) parameters indicate that most of these minerals have a moderate to high hydrophobicity. The interfacial tension values are consistent with the order of the solubilities of these minerals.     

Synthesis of Drim-7,9(11)-diene and Its Hydroxylated Derivatives

This article describes a new efficient synthesis of drim-7,9(11)-diene and its hydroxylated derivates from drim-8-en-7-one. Reduction of this ketone with NaBO₄ in the presence of CeCl₃ · 7H₂O afforded regio- and stereoselectively drim-8-en-7β-ol in a high yield. Its dehydration with H₂SO₄ under mild conditions led to drim-7,9(11)-diene. Noncatalytic oxidation of drim-7,9(11)-diene with OsO₄ and the catalytic oxidation with the pair OsO₄–NMO gave, in a high yield, depending on conditions, driman-7β,8β,9α,11-tetraol or its mixture with drim-7-en-9α,11-diol and drim-9(11)-en-7α,8α-diol. Under optimal conditions the total yield of these diols reached 89%. The separate, noncatalytic oxidation of drim-7-en-9α,11-diol and of drim-9(11)-en-7α,8α-diol with OsO₄ afforded driman-7α,8α,9α,11-tetraol.     

Effect of Polymer on Dynamic Interfacial Tensions of Anionic–nonionic Surfactant Solutions

The dynamic interfacial tensions (IFTs) of enhanced oil recovery (EOR) surfactant/polymer systems against n-decane have been investigated using a spinning drop interfacial tensiometer in this paper. Two anionic–nonionic surfactants with different hydrophilic groups, C₈PO₆EO₃S (6-3) and C₈PO₆EO₆S (6-6), were selected as model surfactants. Partially hydrolyzed polyacrylamide (HPAM) and hydrophobically modified polyacrylamide (HMPAM) were employed. The influences of surfactant concentration, temperature, polymer concentration, and oleic acid in the oil on IFTs have been studied. The experimental results show that anionic–nonionic surfactants can form compact adsorption films and reach ultralow IFT (10^?3 mN/m) under optimum conditions. The addition of polymer has great influence on dynamic IFTs between surfactant solutions and n-decane mainly by the formation of looser mixed films resulting from the penetration of polymer chains into the interface. The compact surfactant film will also be weakened by the competitive adsorption of oleic acid, which results in the increase of IFT. Moreover, the penetration of polymer chains will be further destroyed surfactant/polymer mixed layer and lead to the obvious increase of IFT. On the other hand, polymers show little effect on the IFTs of 6-6 systems than those of 6-3 because of the hindrance of longer EO chain of 6-6 at the interface.     

The Interfacial Tension and Alkane Carbon Number (nmin) of Alkyl Benzene Sulfonates in Relation to Enhanced Oil Recovery. Part I: Effect of Surfactant Molecular Weight/Temperature and Electrolyte on nmin

Twelve anionic monoisomeric surfactants based on the alkyl benzene sulfonic acid were prepared. In two sets of experiments, the (n_min) values were determined at 28 and 70°C for them. The n-hydrocarbon scans (n-C₅ to n-C₁₈) against the interfacial tension were used to determine the (n_min) values. The factors affecting (n_min) such as; molecular weight, branching of side chain, temperature and electrolyte addition were investigated. From the obtained results, it was found that the surfactants which has the highest molecular (8φ C₁₅ ABS) gave (n_min) equal 8, so it can be used in the enhanced oil recovery(EOR) without additives (the suitable (n_min) for EOR between 7-9). Otherwise, the lowest molecular weight surfactant (7φ C₁₃ ABS) gave (n_min) equal 5 without addition of alcohols or electrolyte. This case needs some additives to adjust the (n_min) in the range of 7 to 9. By investigation the factors affecting (n_min), it was found that the side chain of alkyl benzene shifted the (n_min) to the highest values. The increasing of temperature decreased the (n_min) values. Also, it was found that the (n_min) increased to high value by adding the electrolytes and alcohols. The mixture between surfactants with and without side chain shifted the (n_min) to the highest value. Using these parameters, the alkane carbon number (n_min) can be used to select the suitable solvent during the preparation of emulsion to get the minimum interfacial tension at which the maximum emulsion stability should be obtained and also to select the surfactant for EOR.     

Studies on the Effects of Additional Components on Micellization of CTAB via Surface Tension Measurements

The effects of Tris-HCl buffer solution on the cmc of cetyltrimethylammonium bromide (CTAB) were studied by surface tension measurement. The result shows that the effect of the buffer solution depends on the interaction between CTAB and NaCl and the structure accelerants of water, Tris. A series of parameters, including the critical micelle concentration (cmc), the surface tension at cmc (γ_cmc), the adsorption efficiency (pC₂₀), and the effectiveness of surface tension reduction (∏_cmc) were obtained from the surface tension measurements in the presence of glycine with different concentration in the Tris-HCl buffer solution at 27°C. In addition, maximum surface excess concentration (Γ _max) and minimum surface area per molecule (A_min) at the air-water interface were estimated according to the Gibbs adsorption isotherm. The thermodynamic parameters (Δ C _p,m , Δ H _m,tr , Δ C _p,m,tr ) of micellization for CTAB in the absence and presence of glycine at different temperature were also been obtained.     

Ultrasonically Assisted Rate Enhancements in Trichloroisocyanuric Acid/DMF/NaNO2 Triggered Nitration of Aromatic Compounds and Decarboxylative Nitration of α,β-Unsaturated Acids

An efficient and safe method for nitration of aromatic compounds and decarboxylative nitration of α,β-unsaturated acids was developed using trichloroisocyanuric acid (TCICA)/dimethylformamide (DMF) in the presence of NaNO₂. The reaction times of conventional protocol reduced from 8–10 h to 1.0–1.5 h (60–90 min) under sonication, even though the yields are comparable under both the conditions.     

Macrocyclised pheynyl cinnamate dimer utilisable as photoresponsive chiral dopant for nematic liquid crystals

A macrocyclised phenyl cinnamate dimer with a chiral spacer was prepared, and its photochemistry was compared with that of a precursor linear dimer and corresponding monomeric compounds. Although ultraviolet irradiation of the monomer resulted merely in cis–trans isomerisation of a cinnamate, irradiation of the cyclic and linear dimers induced intra-molecular [2 + 2] photodimerisation of cinnamate groups. Photodimerisation in the cyclic dimer proceeded 20 times faster than in the linear dimer. In a nematic liquid crystal, the cyclic dimer exhibited a high helical twisting power of 27.5 μm^?1, which decreased to 6.7 μm^?1 with dimerisation. A macrocyclised dimer such as this can be used as a photoresponsive chiral dopant for nematic liquid crystals.     

Study of Aqueous Biomolecules with Magnetic Flux Using Density,Viscosity, and Surface Tension Probe at 304.15 K

Doses of 0.0150 weber m^?2 magnetic flux for 30 minutes are given to four series of biomolecules in aqueous medium, densities (ρ), viscosities (η), and surface tension (γ) were measured at 304.15 K. The vitamins and carbohydrates decrease densities and viscosities and the difference of density from magnet to aqueous solution in order of dextrose (? 0.00025 kg m^?3) > fructose (? 0.00021 kg m^?3) = B6 (? 0.00021 kg m^?3) > starch (? 0.00018 kg m^?3) > B1 (? 0.0018 kg m^?3), while viscosity in order of starch (? 0.0044 kg m^?1s^?1) > fructose (? 0.0037 kg m^?1s^?1) > B1(? 0.0018 kg m^?1s^?1) > dextrose (? 0.0016 kg m^?1s^?1) > B6 (? 0.0012 kg m^?1s^?1). The surface tension also decreases in vitamin and carbohydrate. The proteins show increase in ρ, η, and γ value hence casein decrease the density and viscosity. The glutamine show increase in density and surface tension while decrease in viscosity and vice versa to alanine. These orders of the data indicate the intermolecular force between water and bimolecules in magnetic flux.     

Microwave-Assisted,Rapid, Solvent-Free Aza-Michael Reaction by Perchloric Acid Impregnated on Silica Gel

Highly efficient solvent-free aza-Michael additions of a variety of amines to α,β-unsaturated carbonyl compounds under microwave-irradiation conditions catalyzed by perchloric acid impregnated on silica gel (HClO₄/SiO₂) is reported. The reactions are completed within 2–7 min in a microwave oven to produce the corresponding adducts in excellent yields, and the catalyst can be recovered and reused.     

Highly Efficient Michael Addition Reaction of Amines Catalyzed by Silica-Supported Aluminum Chloride

Aliphatic and aromatic amines undergo smooth nucleophilic addition to α,β-unsaturated compounds in the presence of a catalytic amount of silica-supported aluminum chloride at 60 °C and under solvent-free conditions to produce the corresponding β-amino compounds in excellent yields. This method is simple and convenient and works efficiently under mild conditions. This catalyst can used again without losing its activity three times.     

Simultaneous Chiral Separation of Geometry Isomers and Enantiomers of Nateglinide by Capillary Electrophoresis with Mixture of CD Derivations as Chiral Selector

Abstract

A capillary electrophoresis (CE) method for the simultaneous separation of geometry isomers and enantiomers of nateglinide was built. Several different dyclodextrin (CD) derivatives were tested for the chiral separation of nateglinide, and it was proved that ionic CDs [i.e., carboxymethy-β-CD (CM-β-CD) and sulphonic-β-CD (S-β-CD)] could show better chiral selectivity for both geometry isomers and enantiomers than the neutral CDs. The separation of geometry of both isomers and enantiomers of nateglinide was obtained by CE in a 75-µm i.d. × 60 cm (effective length 45 cm) fused-silica capillary at 11 kV voltage, while 30 mM phosphate (pH = 8.38) acted as running buffer and a mixture of 40 mM S-β-CD + 21 mM CM-β-CD served as chiral selector. The detective wavelength was set at 254 nm.     

Mild and Efficient Syntheses of 1-Aryl-3,4-dihydroisoquinolines and 1-Aryl-3,4-dihydro-β-carbolines via Regiospecific β-Eliminations of the Corresponding N-Tosyl-1,2,3,4-tetrahydroisoquinolines and N-Tosyl-1,2,3,4-tetrahydro-β-carbolines

Treatment of N-tosyl-1-aryl-1,2,3,4-tetrahydro-isoquinolines or N-tosyl-1-aryl-1,2,3,4-tetrahydro-β-carbolines with a strong base such as NaOH or KOH at 70 °C in dimethylsulfoxide (DMSO) produced 1-aryl-3,4-dihydroisoquinolines or 1-aryl-3,4-dihydro-β-carbolines in good yields via mild and regiospecific β-eliminations. A dramatic solvent effect was observed, DMSO was crucial for the reactions. The temperature is also crucial for the reactions and should be kept between 60 and 80 °C.