Freezing point behavior of the ternary reciprocal salt pair system involving the morpholine and 2,2′-dipyridylamine salts of stearic and palmitic acids

Binary and quasi-binary freezing point data have been obtained to establish the freezing point diagram for the ternary reciprocal salt pair system, involving the morpholine and 2,2′-dipyridylamine salts of stearic and palmitic acids. The diagram shows that there are six crystallization surfaces representing equilibrium with crystals of MS, MP, DS, DP, DS·DP, and MS·DP. The compositions and primary freezing points of the six peritectic and five eutectic mixtures have been determined. From the diagram it is possible to predict for any molten mixture of these four salts under equilibrium conditions the temperature at which crystals of each component will appear on cooling, the yields of these crystals and the composition of the liquid phase at various temperatures, and the temperature at which maximum yields of crystals of the specific salts can be obtained. Presented at AOCS meeting in New Orleans, La., May 7–9. 1962. One of the laboratories of the Southern Utilization Research and Development Division, Agricultural Research Service, U.S.D.A.     

Preparation of pure palmitic acid and a by-product plasticizer from cottonseed oil

Summary A laboratory process has been developed which permits the isolation of a highly purified palmitic acid from cottonseed acids through the recrystallization of its cyclohexylamine salt from acetone and subsequent regeneration of the acid. The by-product, predominantly cyclohexylamine salts of the unsaturated fatty acids, can be modified and converted to morpholides which have shown promise as vinyl plasticizers. The morpholine salts can be obtained as a direct byproduct by the use of an appropriate mixture of cyclohexylamine and morpholine with the composite acid. By using an amount of cyclohexylamine closely equivalent to the saturated fatty acid content and sufficient morpholine to make up the residual neutralization equivalent of the composite cottonseed acids, the saturated acids can be isolated as cyclohexylamine salts. The stripped mother liquor will consist essentially of the morpholine salts of the unsaturated acids. Pure palmitic acid is obtained by recrystallization of the cyclohexylamine salts. The complete process is applicable to fatty acids from other natural glyceridic oils in which the dominant saturated acid bears a ratio to the other saturated acids closely paralleling that in cottonseed oil. The process is not operable with partially hydrogenated oils. Presented at the 49th Annual Meeting of the American Oil Chemists’ Society, Memphis, Tenn., April 21–23, 1958. One of the laboratories of the Southern Utilization Research and Development Division, Agricultural Research Service, U. S. Department of Agriculture.     

Crystallization Behavior of Fatty Acid Methyl Esters

Biodiesel from most agricultural feedstocks has flow properties that are prone to startup and operability problems during cold weather. Biodiesel from soybean oil is generally a mixture of long-chain fatty acid alkyl esters composed of 0.15–0.20 mass fraction saturated esters (melting point [MP] ≫ 0 °C) mixed with unsaturated esters (MP < 0 °C). This work investigates the crystallization properties of two saturated fatty acid methyl esters (FAME) commonly found in biodiesel from soybean oil. Differential scanning calorimetry (DSC) heating and cooling scans of methyl palmitate (MeC16), methyl stearate (MeC18) and methyl oleate (MeC18:1) in pure form were analyzed. Crystallization behavior in ternary FAME mixtures was inferred by the application of thermodynamic models based on ideal solution and freezing-point depression theories. Activity coefficients for MeC16 and MeC18 in MeC18:1 solvent were determined by analyzing DSC cooling curves for binary FAME mixtures. Eutectic points were predicted by both models. Crystallization onset temperatures inferred from freezing point depression theory were more accurate than those for ideal solutions with respect to a direct DSC cooling curve analysis of corresponding ternary mixtures. This work shows that the crystallization onset temperature (cloud point) of biodiesel may be predicted by freezing-point depression theory if the activity coefficients of the component FAME are known. The use of trade, firm, or corporation names in this publication is for the information and convenience of the reader. Such use does not constitute an official endorsement or approval by USDA or ARS of any product or service to the exclusion of others that may be suitable.     

Binary freezing-point diagrams for palmitic acid with various amines and with 2,6-dimethyl-gamma-pyrone

Summary In connection with the search for molecular compounds which might prove applicable in the purification of long-chain fatty acids, freezing-point data have been obtained for binary systems between palmitic acid and the following: ortho-phenylenediamine, alpha-picoline, 4-amino-2,6-dimethylpyrimidine, 2,6-dimethyl-gamma-pyrone, 2-aminothiazole, benzylamine, morpholine, 3-aminopyridine, and 4-aminopyridine. The freezing-point diagrams for the first four of these binary systems are of the simple eutectic type. All the others indicate the existence of at least one crystalline molecular compound containing one or more moles of palmitic acid to one of amine. 2-Aminothiazole forms an equimolar compound. Both benzylamine and morpholine form an equimolar and an incongruently melting 2∶1 compound. The position of the amino group in the pyridine ring has a marked effect on the behavior of the aminopyridines. Unlike 2-aminopyridine, which forms a 1∶1 and a 4∶1 compound with palmitic acid, 3-aminopyridine forms only an equimolar compound and 4-aminopyridine forms only 4∶1 and 2∶1 compounds. The latter exists in two polymorphic modifications. One of the laboratories of the Southern Utilization Research and Development Division, Agricultural Research Service, U. S. Department of Agriculture.     

三元水盐体系冰点和共晶点的测定、相图表达及计算

针对Na⁺//Cl^-,NO₃^--H₂O、Na⁺//Cl^-,SO₄^2--H₂O和Na⁺,K⁺//Cl^--H₂O 3个三元水盐体系,测定了不同组成时溶液的冰点、共晶点以及降温过程的析盐规律,绘制出三元体系温度-组成立体相图。结果表明：三元体系的冰点、共晶点、相关系与组成可用三棱柱表达,3个三元水盐体系在共晶点温度下均无复盐存在,各含有1个两盐与冰的共晶点,3条单盐与冰或盐盐的共晶线,1个冰和两个单盐结晶区;用三元体系温度-组成立体相图能更直观地表达三元水盐体系的结晶区、冰点、共晶点和溶液组成的关系,可以判断溶液降温过程中的盐或冰的析出类型、温度;同时建立了冰点经验公式,应用经验公式和过量吉布斯自由能模型预测三元体系的冰点和共晶点,计算值和实验值吻合良好。     

Dilatometric investigations of fatty acid methyl esters

Summary The coefficients of expansion and melting dilations were measured for methyl palmitate, methyl stearate, methyl arachidate, methyl behenate, and methyl oleate. The dilatometric curve for the heating cycle of methyl palmitate and methyl stearate in the solid state was composed of a linear section to 49 degrees below the melting point, followed by a curvilinear section to the melting point. The heating and cooling cycle curves for methyl palmitate show the same volume change from −38°C. to 29°C., but the shape of the curves is different. The same relation holds for methyl stearate from −38°C. to 37.5°C. “After-contractions” were found in volume measurements within a few degrees of the melting point of both esters. Equilibrated points were found within 0.5 degrees of the final melting temperature of methyl stearate. A striking similarity exists between curves for variation of the dielectric constant with temperature for long chain linear molecules and the dilatometric data. Presented at the fall meeting, American Oil Chemists' Society, Mnneapolis, Minn., October 11, 1954. Issued as Paper No. 196 on the “Uses of Plant Products” and as N.R.C. No. 3671.     

三元体系NaBr-Na2B4O7-H2O在373 K的相平衡研究

采用等温溶解平衡法研究了三元体系NaBr-Na2B4O7-H2O在373 K时的相平衡关系,并测定了饱和溶液的溶解度及密度。研究发现：该三元体系为简单共饱和型,无复盐及固溶体形成。根据溶解度数据绘制了相应的平衡溶解度曲线,相图中有1个共饱点,2条单变曲线,2个平衡固相分别为NaBr和Na2B4O7·5H2O;对不同温度条件下的溴化钠和硼酸钠的溶解度做了对比分析和讨论,结果表明,随着温度的增加,硼酸钠和溴化钠的溶解度均增大,但是在高温条件下,硼酸钠其溶解度数据增加明显;在该三元体系中溴化钠对硼酸钠有明显的盐析作用;并简要讨论了密度变化规律。     

Selective use of palmitic acid over stearic acid for synthesis of phosphatidylcholine and phosphatidylglycerol in lung

The incorporation of [³H]palmitic acid and [¹⁴C]stearic acid into phospholipids in rabbit lung tissue was studied. Under equal molar concentrations of palmitate and stearate, palmitate was incorporated to the 1- and 2-positions of phosphatidylcholine (PC) and phosphatidylglycerol (PG) 2–3 times more than stearate. By contrast, palmitate was 30% less than stearate in phosphatidylethanolamine, phosphatidylinositol and phosphatidylserine. These results suggest that preferential utilization of palmitate over stearate, rather than substrate availability, determines the high content of palmitoyl at the 1- and 2-positions of PC and PG in lung.     

Studies on the behaviour of chromium (iii) soaps. II. Solubility and viscometric studies with chromium stearate and palmitate in nonaqueous solutions

The colloid chemical behaviour of the chromium stearate and palmitate in nonaqueous solutions have been investigated by solubility and viscometric methods. Chromium stearate and palmitate form no micellar aggregate in pyrindine but aggregate into micelles in benzene, toluene, xylene and carbon tetrachloride in the concn range of ca. 0.7–1.5×10⁻² mole/liter. Viscometric studies can be utilized in estimating the concn of the metal soaps in fairly concd solution: 0.822–27.431 g/liter.     

多元水盐体系冰盐共晶点的测定和图形表达

水盐体系共晶点的数据可以为盐湖卤水低温加工工艺开发提供必要的理论依据,采用低温冷却法,针对四元同离子体系K⁺//Cl^-,SO₄^2-,NO₃^--H₂O和四元交互体系Na⁺,K⁺//SO₄^2-,NO₃^--H₂O及其相关的6个三元子体系,测定研究了其冰点、共晶点以及析盐规律,绘制出了共晶点温度-液相组成图。研究结果表明:通过测定多元水盐体系降温过程中的时间-温度图,可以判断盐类析出规律、测定冰和盐的共晶点温度;上述体系中,常温下存在的复盐钾芒硝,在共晶点温度下均不再出现,水盐体系相关系得以简化;用棱柱图可以简单直观地表达三元体系、四元同离子体系和四元交互体系的相、冰点或共晶点的温度和溶液组成的关系;在三元体系的共晶点温度-液相组成图中,存在两条单盐与冰的共晶线、一个两种盐与冰的共晶点、一个冰析出面;在四元同离子体系和四元交互体系共晶点温度-液相组成图中,分别有3个和4个单盐与冰的共晶面、3条和5条两种盐与冰的共晶线、1个和2个3种盐与冰的共晶点。     

Stearic acid unlike shorter-chain saturated fatty acids is poorly utilized for triacylglycerol synthesis and β-oxidation in cultured rat hepatocytes

Utilization of stearate as compared to various saturated fatty acids for cholesterol and lipid synthesis and β-oxidation was determined in primary culture of rat hepatocytes. At 0.5 mmol/L in the medium, stearate (18:0) adequately solubilized by albumin was less inhibitory to cholesterol synthesis from [2-¹⁴C] acetate than myristate (14:0) and palmitate (16:0) (68% vs. 91 and 88% inhibition, respectively). The rate of incorporation into cholesterol from [1-¹⁴C] stearate (3.0±0.6 nmol/mg protein/4 h) was 37-, 1.8-, and 7.8-fold of that from myristate, palmitate, and oleate, respectively. Conversely, the rate of [1-¹⁴C] stearate incorporation into total glycerolipids was 88–90% lower than that of labeled palmitate, myristate, and oleate. The rate of [1-¹⁴C] stearate incorporation into triacylglycerol (3.6±0.4 nmol/mg protein/4 h) was 6–8% of that from myristate, palmitate, oleate, and linoleate. The rate of stearate incorporation into phospholipids was the lowest among tested fatty acids, whereas the rate of mono- and diacylglycerol synthesis was the highest with stearate treatment. The rate of β-oxidation as measured by CO₂ and acid soluble metabolite production was also the lowest with [1-¹⁴C] stearate treatment at 22.7 nmol/mg protein/4 h, which was 35–40% of those from other [1-¹⁴C] labeled fatty acids. A greater proportion of stearate than other fatty acids taken up by the hepatocytes remained free and was not metabolized. Clearly, stearate as compared to shorter-chain saturated fatty acids was less efficiently oxidized and esterified to triacylglycerol in cultured rat hepatocytes.     

Vapor pressure measurements on saturated biodiesel fuel esters by the concatenated gas saturation method

The purpose of this work was to determine vapor pressures for saturated biodiesel esters at the low-temperature end of their liquid range. A “concatenated” gas saturation apparatus capable of simultaneous measurements on 18 samples was used for measurements on methyl palmitate, ethyl palmitate, methyl stearate, ethyl stearate, and eicosane (C₂₀H₄₂) over the temperature range 323.15 K-343.15 K. Eicosane, a linear alkane with a well known vapor pressure curve (in the same range as the biodiesel esters), was included as a control compound. Importantly, the measured vapor pressures for eicosane are in excellent agreement with reference values, which is good evidence of the low uncertainty of the measurements on the biodiesel esters. Over this temperature range, the measured vapor pressure ranges were 0.145 Pa-1.11 Pa for methyl palmitate, 0.0687 Pa-0.616 Pa for ethyl palmitate, 0.0159 Pa-0.183 Pa for methyl stearate, and 0.00704 Pa-0.0912 Pa for ethyl stearate. The combined standard uncertainty in the vapor pressure measurements ranged from 8% to 15%.     

Properties of the fatty acid esters of amylose

To help establish the suitability of esters of amylose and fatty acids as dip-coating materials, esters of the evennumbered, saturated fatty acids, acetic through stearic, and of oleic and cottonseed oil fatty acids were prepared, and their properties were determined. The various esters generally were prepared by the interaction of acid chlorides with the amylose suspended in a suitable mixture of solvents. Analyses for content of free fatty acid groups indicated that high proportions of the hydroxyl groups were esterified. Intrinsic viscosity decreased as the chain length of the acyl group increased, a reflection of the changing nature of the products rather than a decrease in the degree of polymerization of the amylose. As the chain length of the saturated fatty acid group increased the softening point at first decreased and then increased, the minimum being obtained with the myristate. The stearate softened at 56.2°C. The stearate had a hardness index of 139, which was about equal to the index of 140 for completely hydrogenated cottonseed oil. Densities were greater than those of the corresponding triglycerides and decreased as the chain length of the fatty acid group increased. Permeability to water vapor also decreased as the chain length increased, the index being 620×10⁻¹² for the acetate and 15×10⁻¹² for the stearate. The acetate possessed the highest tensile strength, about 4.40 kg./sq. mm., while the palmitate had a tensile strength of about 0.49 kg./sq. mm. Elongation at the break point varied widely, being 632% for the caprate and 0.95% for the stearate. Presented at the 52nd Annual Meeting of the American Oil Chemists' Society, St. Louis Missouri, May 1–3, 1961. One of the laboratories of the Southern Utilization Research and Development Division, Agricultural Research Service, U.S. Department of Agriculture.     

Oxygen absorption of methyl esters of fat acids,and the effect of antioxidants

Summary The oxygen absorption of methyl linolenate, methyl linoleate, methyl oleate, methyl stearate, the distilled methyl esters of lard, and various mixtures of the four individual methyl esters were measured at 100° C. in the Barcroft-Warburg apparatus. Mixtures of methyl esters absorbed oxygen at a rate which could be approximately predicted from the rate of oxygen absorption of each component and the percentage of each present. The antioxidants nordihydroguaiaretic acid (NDGA), propyl gallate, benzylhydroquinone, α-tocopherol, and their synergistic combinations with citric acid, d-isoascorbyl palmitate, and lecithin were tested with the substrates methyl linoleate, methyl oleate, methyl stearate, and the distilled methyl esters of lard. Citric acid showed marked synergism with each antioxidant. The two most effective were the combinations of citric acid with nordihydroguaiaretic acid and with propyl gallate. One of the laboratories of the Bureau of Agricultural and Industrial Chemistry, Agricultural Research Administration, United States Department of Agriculture.     

The fate and intermediary metabolism of stearic acid

Coming from the Greek for “hard fat”, stearic acid represents one of the most abundant FA in the Western diet. Otherwise known as n-octadecanoic acid (18∶0), stearate is either obtained in the diet or synthesized by the elongation of palmitate, the principal product of the FA synthase system in animal cells. Stearic acid has been shown to be a very poor substrate for TG synthesis, even as compared with other saturated fats such as myristate and palmitate, and in human studies stearic acid has been shown to generate a lower lipemic response than medium-chain saturated FA. Although it has been proposed that this may be due to less efficient absorption of stearic acid in the gut, such findings have not been consistent. Along with palmitate, stearate is the major substrate for the enzyme stearoyl-CoA desaturase, which catalyzes the conversion of stearate to oleate, the preferred substrate for the synthesis of TG and other complex lipids. In mice, targeted disruption of the stearoyl-CoA desaturase-1 (SCD1) gene results in the generation of a lean mouse that is resistant to diet-induced obesity and insulin resistance. SCD1 also has been shown to be a key target of the anorexigenic hormone leptin, thus underscoring the importance of this enzyme, and consequently the cellular stearate-to-oleate ratio, in lipid metabolism and potentially in the treatment of obesity and related disorders.     

Phase behavior of homologous series of monoesters of polyols

Phase behavior of anhydrous monopalmitates and stearates and of most laurates, myristates and behenates of ethylene glycol, erythritol, xylitol, sorbitol, and mannitol has been studied. The compounds, substantially free of diesters, are mostly not isomerically pure but are predominantly primary esters. Also studied were the (nonisomeric) palmitate and stearate of pentaerythritol (Pe) and the oleate of erythritol. Mesomorphism, absent in anhydrous monoglycerides unless of short chain length and symmetrical, is a prominent feature of the members of the present group of compounds containing at least three unesterified hydroxyls. In general, crystal melting points rise with length of polyol, and mesomorphic melting points rise faster. Crystal melting points rise with acyl chain length while mesomorphic melting points run through a maximum. Heats of fusion are of the order 40 cal/g for crystal melting and 0.5 cal/g for melting of mesomorphic states. In the range explored, mesomorphic values fall with both polyol length and acyl length. At higher acyl chain length, notably with behenates, there are new features of mesomorphic behavior. Crystalline phase, from solvent, melts to a neat or lamellar phase, which in turn melts to liquid with subsequent appearance of higher melting middle or cylindrical phase. Polymorphism is general among the crystal states and tends to be complex. In a brief study of solvent crystallized 50–50 binary mixes of xylitol stearate with other xylitol esters and other stearates, considerable evidence of solid solution in Form I crystals (of xylitol stearate type) was observed with very modest eutectic lowering of crystal melting point. Mesomorphic points were almost linearly intermediate between those of components. Of particular interest were mixtures of xylitol stearate and 1-monostearin (50–50 and 25–75), for which mesomorphic melting points were realized, and for which an extrapolation to 100% monostearin leads to a hypothetical mesomorphic melting point far below any monoglyceride crystalline melting point. A brief examination of an aqueous xylitol palmitate system explored to a maximum temperature of 165 C shows extensive occurrence of aqueous mesomorphic state somewhat after the manner of monoglyceride systems. Mesomorphic melting level rises rapidly from the value for anhydrous ester.     

Cell-culture compatible silk fibroin scaffolds concomitantly patterned by freezing conditions and salt concentration

The morphology of freeze-dried silk fibroin 3D-scaffolds was modified by varying both the NaCl concentration and the freezing temperature of the silk fibroin solution prior to lyophilization. Scanning electron micrographs showed that slow freezing at −22 °C generated sponge-like interconnected porous networks, whereas fast freezing at −73 °C formed stacked leaflet structures. The presence of millimolar NaCl (50–250 mM) increased the porosity of the scaffolds and generated small outgrowths at their surface, depending on the freezing regime. Our results suggest that the morphological differences seen between the materials likely depend on ice and NaCl hydrate crystal nucleation and growth mechanisms. Infrared spectroscopy and X-ray diffraction analyses revealed that the salt concentration and freezing conditions induced no structural changes in fibroin. The seeding of P19 embryonic carcinoma cells showed that the presence of salt and freezing conditions influenced the cell distribution into the scaffolds, with salt addition increasing the access of cells to deeper regions.     

Antioxidative properties and enzymatic synthesis of ascorbyl FA esters

Efficient synthesis of unsaturated FA esters of ascorbic acid is possible with only a small excess of one of the reactants in t-amyl alcohol using Candida antarctica lipase as biocatalyst. Using free acids, we obtained yields that were comparable to yields reached using vinyl-activated acyl donors (71, 80, and 86% yields of esters with FA excesses of 1∶1, 1∶1.5, and 1∶2, respectively). As very low water activity is needed to achieve sufficiently high yields of product, molecular sieves were used to improve the ascorbyl ester yields. Ascorbyl oleate is more amorphous and has a much lower m.p. and lower enthalpy of fusion than ascorbyl palmitate. This leads to a higher solubility of ascorbyl oleate in oil, resulting in an increased antioxidant effect compared to that of the palmitate. In an accelerated storage test using deodorized rapeseed oil, samples incubated with ascorbyl palmitate showed noticeable oxidation after 1 wk of storage, whereas samples incubated with ascorbyl oleate displayed negligible oxidation for 9 and 4 wk at 30 and 40°C, respectively.     

K_2CO_3-KCl-H_2O三元体系298K介稳相平衡研究

本文报道西藏扎布耶盐湖卤水三元子体系K2CO3-KCl-H2O 298 K介稳平衡实验数据,并绘制出介稳平衡相图.结果表明:该三元体系属简单共饱型,无复盐或固溶体形成;介稳平衡相图中单变度曲线(AE和BE)对应的介稳平衡固相分别为:K2CO3·3/2HO和KCl.与该体系对应的稳定相图比较:氯化钾、碳酸钾石与平衡相图中结晶形式一致.     

Identification and quantification of important steryl esters in aspen wood

Steryl esters make up a major portion of the total lipids in aspen wood, and contribute significantly to pitch deposit problems during pulping. Fungal treatment of aspen is an attractive method for removing these compounds because it is inexpensive and environmentally acceptable; however, the mechanism of steryl ester removal remains unclear. Identification of the steryl esters will lead to a better understanding of how they are removed by fungi. The steryl ester fraction from aspen wood was obtained by acetone extraction then further purified by silica gel column chromatography and argentation-silica gel column chromatography. This led to the isolation of three major fractions: fraction I, fraction II, and fraction III. The major steryl esters of fractions I and II were identified by gas chromatography, gas chromatography-mass spectroscopy, and proton nuclear magnetic resonance analysis of the intact fraction as well as sterol and fatty acid moieties obtained after base hydrolysis. Identification of the steryl esters was carried out by mass spectra comparisons with steryl ester standards synthesized in the laboratory and comparison with mass spectra libraries (Wiley and NIST) by mass fragmentography. Fraction I contained primarily the palmitate, stearate, and eicosanoate esters of α- and β-amyrin. Fraction II consisted mainly of the palmitate, stearate, and eicosanoate esters of tirucalla-7,24-dien-3β-ol and lupeol.