An improved method of characterizing fatty acids by equivalent chain length values

A method has been developed for calculating more accurate and reproducible equivalent chain length (ECL) values of 33 straight-chain fatty acids (FA), with various positions and numbers of cis double bonds, chromatographed on DB-Wax and DB-1 columns. The dependence of ECL values on the position and the number of double bonds is described, as is a method of utilizing these relationships for the characterization of FA by gas chromatography.     

Water-AOT-alkylbenzene microemulsions: influence of alkyl chain length on structure and percolation behavior

We study the percolation behavior of the water-in-oil (w/o) droplet phase of AOT (sodium bis[2-ethylhexyl] sulfosuccinate)-based microemulsions with different alkylbenzenes (toluene, ethylbenzene, butylbenzene or octylbenzene) as oil phase. We use microemulsions of varying composition with molar water to surfactant ratios 0≤W≤ 50 and droplet (water plus surfactant) volume fractions 10%≤φ≤50%. Using dielectric spectroscopy, a percolation transition is observed in w/o microemulsions with butylbenzene or octylbenzene. With increasing molecular weight of the alkylbenzene, the percolation temperature T(P) decreases. The structure of the microemulsions is determined by small angle X-ray scattering (SAXS). With increasing molar weight of the alkylbenzene, the stability range of the L(2) droplet phase extends to higher W. The larger amount of solubilizable water can be related to variable oil penetration of the AOT monolayer, which affects the spontaneous curvature of the surfactant shell.     

Determination of drug and fatty acid binding capacity to pluronic f127 in microemulsions

We propose that one can deduce very insightful information regarding the drug and fatty acid binding capacity of microemulsions through simple turbidity experiments. Pluronic F127-based oil-in-water microemulsions of various compositions were synthesized and titrated to turbidity with concentrated amitriptyline, an antidepressant drug. We observed that, above certain Pluronic F127 concentrations, turbidity was never observed, irrespective of how much amitriptyline was added to the microemulsion. We also observed that whenever sodium caprylate fatty acid was not included in the microemulsion formulation, turbidity never occurred. On the basis of these findings, we were able to determine the point at which all sodium caprylate present in the microemulsion formulation was bound to the F127 in the microemulsion (i.e., no fatty acid was free in the bulk in monomer form). By the same logic we were also able to determine how much amitriptyline was binding to the microemulsions. We also measured the dynamic surface tension, foamability, and fabric wetting time of the microemulsion formulations to further prove the hypothesis that all fatty acid is bound to the F127 in the microemulsion above a critical Pluronic F127 concentration. On the basis of this research, we have concluded that there are approximately 11 molecules of sodium caprylate fatty acid bound per molecule of Pluronic F127 and approximately 12 molecules of amitriptyline bound per molecule of Pluronic F127 in the optimal microemulsion formulation. These findings give us valuable information about the charge density at the oil/water interface and about the mechanism of binding of the drug to the microemulsion.     

Standard equivalent chain length values of monoenic and polyenic (methylene interrupted) fatty acids

The equivalent chain length (ECL) values of the methyl esters of 83 defined fatty acids (FAs) have been determined by gas chromatog-raphy (GC) on three fused silica DB-WAX and three DB-1 columns. ECL values of further 46 FAs were calculated by different methods. Conditions of chromatography, methods of ECL values calculation and differences between ECL values on individual columns and between trans- and cis-isomers of corresponding FAs are also discussed.     

Nonmonotonic pattern of the critical percolation temperature due to variations of additive chain length in water-in-oil microemulsions

The nonmonotonic variation of the critical percolation temperature (T _c) of ternary nonionic (C₁₄E₅) water-in-oil microemulsions was studied as a function of the alkyl chain length of an ionic additive (n-alkyl sulfonate sodium salt). A thermodynamic approach shows the relationship between T _c and additive chain length, which is supplemented by a consideration of a possible molecular mechanism of the observed phenomenon. Received: 20 October 2000 Accepted: 7 November 2000     

Effect of chain length distribution on the phase behavior of polyglycerol fatty acid ester in water

The effect of the chain length distribution on the phase behavior, the structure of liquid crystals, and physicochemical properties was investigated in water/ polyglycerol fatty acid ester. Polyglycerol fatty acid esters with sharply distributed polyglycerol (10G*0.7L) and with broadly distributed polyglycerol (10G0.7L) were used. Unreacted polyglycerol in both surfactants was removed. 10G*0.7L forms hexagonal liquid crystals at a higher concentration than 10G0.7L. The effective cross-sectional area of the lipophilic parts in the hexagonal phase of 10G0.7L is smaller than that of 10G*0.7L owing to the difference in the chain length distribution. Evidently, 10G0.7L molecules are tightly packed in aggregates; therefore, 10G0.7L decreased the surface tension more strongly and promoted emulsification. Received: 11 January 2000 Accepted: 8 March 2000     

Effect of surfactant chain length on the binding interaction of a biological photosensitizer with cationic micelles

Steady-state and time-resolved fluorometric techniques have been exploited to study the photophysical and distribution behavior of an efficient cancer cell photosensitizer, norharmane (NHM), in well-characterized, biomimicking nanocavities formed by cationic micelles with varying surfactant chain length. Amphiphiles like dodecyl trimethyl ammonium bromide (DTAB), tetradecyl trimethyl ammonium bromide (TTAB), and cetyl trimethyl ammonium bromide (CTAB) have been used for the purpose. Emission behavior of NHM is very much dependent on the surfactant concentration as well as their hydrophobic chain length. The binding constant (K) and free-energy change (DeltaG) for the interaction of NHM with the cationic micelles have been determined from the fluorescence data. Polarity of the microenvironment around the probe has been determined in the cationic micellar environments from a comparison of the variation of fluorescence properties of the two-prototropic species of the probe in water/dioxane mixture with varying composition. Experimental results demonstrate that the variation in the cationic surfactant chain length plays an important role in promoting a specific prototropic form of the probe molecule. Fluorescence decays are biexponential in all the micelles indicating that the probe molecules are distributed between the two distinct regions of the micelles. The population of the component with a longer lifetime corresponds to the probe in the head group site, while the short-lived component comes from the probe bound to the core region of the micelles. On the basis of the lifetime measurements, the partitioning behavior of the chromophore in the head group and in the core regions in the micelles has been determined.     

Degree of counterion binding on water in oil microemulsions

An ion-exchange process has been used to prepare HOT from NaOT (sodium bis(2-ethylhexyl)sulfosuccinate), where the Na(+) counterion has been replaced by H(+). The acidity function, H(0), of the aqueous core of HOT-based microemulsions decreases with W from H(0) approximately 0.6 at W>20 to H(0)=-1.4 at W=2. On the basis of the H(0) acidity function of the aqueous core and the dependence of H(0) on acid concentration, we have been able to determine the degree of counterion binding (beta) in microemulsions with a value of beta approximately 0.92 which is practically independent of the water content of the system.     

有效碳链长度与脂肪醇的沸点

脂肪醇沸点(b.p.)变化规律可用下述关系式表示:ln(800.386-T~b)=6.64919-2.94828×10^-^2N~E~C~C+0.150955ΔPEI。式中N~E~C~C为醇中烷基的有效碳链长度, ΔPEI是具有相同碳原子数目的支链烷基与直链烷基的极化效应指数的差值, 它表示羟基对醇的沸点的影响。     

Kinetic studies on the permanganic oxidation of amino acids. Effect of the length of amino acid carbon chain

The kinetic study of the permanganic oxidation of some amino acids (glycine, L-alanine, L-α-amino-n-butyric acid, L-norvaline, and L-norleucine) has been carried out in buffered acid medium at 1 < pH < 3 using a spectrophotometric technique. An autocatalytic effect due to Mn²⁺ ions was found in all cases. The purpose of this work is to study the influence of the length of carbon chain of the above amino acids. For it, structural factors such as steric, inductive, and hyperconjugation effects of the carbon chain were analyzed. It was found that the reactivity of these compounds is not affected by only one factor, but the influence of several factors and the formation of intermediate complexes could be included in these oxidative processes. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 181–185, 1997.     

Purity testing of sulfonic acids of different chain length by capillary electrophoresis

Summary A CZE method has been developed for the purity testing of sulfonic acids. By use of an optimized electrolyte system, short analysis times and high resolution (R _S=2–4) can be achieved for inorganic anions and for alkyl sulfonic acids from methane-1- to decane-1-sulfonic acid. By use of indirect UV detection by-products of different sulfonic acids can be determined at the 2 m level, equivalent to 0.02%,w/w. Presented at the 21^st ISC held in Stuttgart, Germany, 15^th–20^th September, 1996     

Effect of carbon chain length of monocarboxylic acids on cloud point temperature of poly(2-ethyl-2-oxazoline)

The temperature-induced phase transition of poly(2-ethyl-2-oxazoline) (PEtOx) aqueous solution under mixing with a series of small carboxylic acids has been studied by turbidity measurements and laser light scattering. It has been found that cloud point temperature (T _cp) of the PEtOx was changed to varying degrees depending upon the pH, ionic strength, molar ratio of acids to 2-ethyl-2-oxazoline unit, and carbon chain length of small carboxylic acids. Significant change in T _cp was observed in the case of hexanoic acid. At acidic pH, an increase in the molar ratio of hexanoic acid to the 2-ethyl-2-oxazoline unit gradually decreased the phase transition temperature of the polymer as compared to the T _cp of pure PEtOx. At original pH 6 (pH?>?pK _a), T _cp shifts to higher value than that of pure PEtOx for lower molar ratios and decreased later on with increasing the molar ratio. The shift in the T _cp is described based on the differences in the driving force of phase transition, including hydrogen bonding between small carboxylic acids and PEtOx polymer and hydrophobic interaction.     

Influence of n-alkyl acids on the percolative phenomena in AOT-based microemulsions

A study was carried out on the influence of the n-alkyl acid addition on the electric percolation of AOT/iso-octane/water microemulsions ([AOT] = 0.5 M and W= [H(2)O]/[AOT] = 22.2). The observed influence has been explained taking into account the organic nature of these molecules and, hence, their capacity of disturbing the structure of the AOT-film. For these reasons, relationships with their molecular structure (chain length) were analysed.     

Effect of length of carbon chain on antioxidation efficiency of o-bisphenols

Conclusions In the oxidation of isotactic polypropylene the highest antioxidant efficiency is shown by an o-bis-phenol, the nuclei of which are linked by a methylene bridge.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2614–2616, November, 1972.