Molal volumes of somen-Fatty acids and their methyl and ethyl esters

The densities of some pure methyl and ethyl esters ofn-fatty acids were determined at temperatures between 10° to 80°C. The molal volumes of these esters and the long-chain fatty acids were correlated with temperature and chainlength. The reciprocals of the average methylene contribution at long-chain and the end group contribution to the molal volumes were found to be linear functions of the temperature. With the introduction of a correction term to account for mutual interaction of the end groups, three equations, one for each of the esters and the acids, were developed. These equations were used to calculate the molal values of the acids with carbon numbers up to 30 and up to 20 for the esters at temperatures ranging from 10° to 100°C. Excellent agreements were obtained between the molal volumes calculated by the equations and those obtained from the literature and experimental data.     

Insect sex pheromones

The half-lives (t _1/2) for evaporative loss ofn-alkyl andn-alkenyl acetates from rubber septa were determined at temperatures varying from 15 to 35 °C. The changes int _1/2 with temperature gave high correlations with the equation, Int _1/2 = H/RT+y _o where H is the heat of vaporization,R is the gas constant,T is the absolute temperature, andy _o is a constant. Half-lives changed dramatically with temperature and the degree of change with temperature increased with increasing molecular weight. For mixtures, component ratios changed with temperature, but the degree was modest. At 20 °C there was a 7.5-fold ratio oft _1/2 between members of the homologousn-alkyl orn-alkenyl acetates differing by two carbon atoms. The large change int _1/2 with temperature and with number of carbon atoms is a consequence of the thermodynamic relationships and the temperature range of pheromone usage. Therefore, a similar degree of change inf _1/2 with temperature and number of carbon atoms will apply to other formulations of the same type (those in which the rate of evaporation is first order). The values oft _1/2 at 20 °C mainly agreed very well with those reported previously at room temperature. However, our previously reported values for pentadecyl and hexadecyl acetate were revised. Half-lives were shown to depend on the vapor pressure of a compound in the formulation substrate, but not on the vapor pressure of the pure compound.Mention of a commercial or proprietary product does not constitute an endorsement by the USDA.     

Determination of physicochemical properties of some fatty acid methyl esters by gas liquid chromatography

Physicochemical data such as vapor pressures (p⁰), heats of vaporization (ΔH_v), activity coefficents at infinite dilution (γ^∞) and excess partial molar entropy (ΔS _e ⁰ ) are considered important for conducting unit processes and designing reactor equipment. Scanty information regarding such data is available in the literature for the higher fatty acid methyl esters. The objective of this research was to determine the physicochemical properties of higher fatty acid methyl esters (C₁₁–C₂₃) by a gas-liquid chromatographic technique with SE-30 and diethylene glycol adipate as stationary phases. Correlations between carbon numbers and various thermodynamic properties have indicated definite trends, which could be useful in predicting the properties of unknown fatty acid methyl esters. The data generated may be useful to chemical engineers in the construction of storage tanks, solvent extractors and distillation columns. IICT communication no. 2993.     

Determination of environmentally relevant physical-chemical properties of some fatty acid esters

Fat models frequently use input parameters that are defined at environmental conditions. In a recently developed gas-liquid chromatography method (GC-VAP), vapor pressures, heats of vaporization, and heat capacity differences (gas-liquid) of fatty acid esters are determined over a large temperature range that includes environmental temperatures. This method also allows an accurate determination of the normal boiling point temperature of a substance. Literature values of vapor pressure, boiling point temperature, and heat of vaporization at 298.15 K for the chosen esters are all in excellent agreement with those determined with the developed method. Correlations between carbon number and heat of vaporization are high.     

Kinetics of the formation of symmetrical wax esters from the corresponding alcohols with the use of hydrobromic acid and hydrogen peroxide

The primary aliphatic alcohols n-octanol, n-decanol, and n-dodecanol have been converted to their corresponding symmetrical esters by using HBr and H₂O₂ in the absence of a solvent. The reaction was carried out at 30, 40, and 50°C and at mole ratios of alcohol to HBr of 1∶0.1, 1∶0.2, 1∶0.3, and 1∶0.5. The rate of the reaction was found to increase with increase in the reaction temperature and concentration of HBr. The maximal conversion of n-octanol was 72% at 40°C and a mole ratio of n-octanol to HBr of 1∶0.5. The kinetics of the reaction have been established, and the reaction was found to be first-order with respect to alcohol and bromine concentration in the organic phase, and second-order with respect to both. The second-order rate constants for n-octanol, n-decanol, and n-dodecanol are 27.08, 32.58, and 37.42 mL mol⁻¹ min⁻¹, respectively, at 40°C. The activation energy for the esterification reaction of n-octanol was found to be 16.32 kcal mol⁻¹.     

Lipase-catalyzed synthesis of lesquerolic acid wax and diol esters and their properties

Lesquerolic acid was and α,Ω-diol esters were synthesized via immobilizedRhizomucor miehei lipase-(Lipozyme) catalyzed esterification of lesquerolic acid and alcoholysis of lesquerella oil. For each wax ester synthesis, when alcohol substrate was present at a slight (ca. 20%) stoichiometric excess and water content was kept low, over 94% of the hydroxy acyl groups were esterified. The extent of reaction and the ratio of monoester to diester produced for α,Ω-diol reactions was controlled by the solubility of diol in the medium. This latter quantity increased as alcoholysis proceeded due to the formation of partial glycerides and monoesters, which increased the polarity of the medium. Alcoholysis reactions were significantly slower when the medium diol content was above saturation. As the diol chainlength increased, diol solubilization decreased, the ratio of monoester to diester decreased, and the extent of hydrolysis increased. Alcoholysis reactions involving either fatty alcohols or diols suffered from acyl migration, which lowered the purity of lesquerolic acid esters. Several lesquerolic acid esters, synthesized on a preparative scale and purified via column chromatography, were evaluated for their properties: density, viscosity, and melting point. Potential applications for lesquerolic acid esters are discussed.     

Olfactory behavior of red flour beetleTribolium castaneum (Herbst) (Coleoptera,Tenebrionidae) towards natural fatty acid esters

The olfactory responses of red flour beetles,Tribolium castaneum (Herbst), to methyl and ethyl ester of C₁₄–C₁₈ fatty acid prepared from tallow were studied. Methyl octadecanoate and ethyl octadecanoate discouraged aggregation of beetle adults. Ethyl 9.12-octadecadienoate acted as a repellent. Methyl pentadecanoate and ethyl tetradecanoate induced copulation at the level of 5 × 10² and 2 × 10³ g, respectively. The maximum response was observed at the level of 5 × 10² g of the same compounds, and these compounds appear to stimulate males only.     

Significance of medium chainn-alkanes as accompanying compounds in hemipteran defensive secretions: An investigation based on the defensive secretion ofCoridius janus

A mixture oftrans-2-hexenal;n-tridecane (60:40, w/w), the natural combination present in the defensive secretion ofCoridius janus (Hemiptera; Pentatomidae) was shown by comparison with similar aldehyde mixtures having longer and shorter chainn-alkanes, to be the optimal combination as a fumigant and a repellent against three test insect species,Anoplolepis longipes, Sitotroga cerealella, andCulex quinquefasciatus. Toxic values obtained for the three insects, respectively: 1/LC₅₀, 1.72, 4.54, and 6.66 ppm while repellencies were 63%, 50%, and 69%. This study revealed that amongt-2-hexenal:n-alkane combinations those with medium carbon chains,viz C-11 and C-12, also possessed high toxicities and repellencies comparable to that of the natural combination while those with shorter and longern-alkanes possessed lower activity. Toxicities and repellencies ofn-alkane series were only moderate to low showing highest toxic values forn-tridecane at 1/LC₅₀, 0.39, 2.32, and 2.32 ppm and repellencies at 31%, 30%, and 32% for the three test insects, respectively. This series, nevertheless, showed similar variation, medium length chains, C-11, C-12, and C-13 showing comparatively higher activity than other alkanes of shorter and longer chains. This study also revealed that the fumigant property of both alkane and aldehyde are of equal importance while repellency is heavily dependent on the aldehyde.     

Preparation of malvalic and sterculic acid methyl esters from Bombax munguba and Sterculia foetida seed oils

A method has been developed for the preparation of highly pure malvalic (cis-8,9-methyleneheptadec-8-enoic) and sterculic (cis-9,10-methyleneoctadec-9-enoic) acid methyl esters starting from Bombax munguba and Sterculia foetida seed oils. The methyl esters of these oils were prepared by sodium methylate-catalyzed transmethylation followed by cooling (6°C) the hexane solution of crude methyl esters and separation of insoluble fatty acid methyl esters by centrifugation in the case of B. munguba and by column chromatography in the case of S. foetida. Subsequently, the saturated straight-chain fatty acid methyl esters were almost quantitatively removed by urea adduct formation. Finally, methyl malvalate and methyl sterculate were separated from the remaining unsaturated fatty acid methyl esters, in particular methyl oleate and methyl linoleate, by preparative high-performance liquid chromatography on C₁₈ reversed-phase using acetonitrile isocratically. Methyl malvalate and methyl sterculate were obtained with purities of 95–97 and 95–98%, respectively.     

Enzymatic preparation of ricinoleic acid esters of long-chain monohydric alcohols and properties of the esters

Apart from the conventional chemical esterification process, long-chain alkyl ricinoleates also can be prepared by enzymatic esterification or by enzymatic alcoholysis with high yield and without undesirable side reactions. On sulfonation to the hydroxyl group, the alkyl ricinoleates produce surface-active compounds. The tetradecyl ricinoleate shows the best surface-active behavior and seems to be much better than that of sulfonated castor oil commonly known as “Turkey Red Oil”.     

n-fatty acids: Comparison of published densities and molar volumes

Because some publishedn-fatty acid densities and molar volumes disagree significantly with others, an attempt was made, based primarily on the principle of homology, to distinguish between reasonably accurate and inaccurate data. Literature densities compatible with each other and with requirements of homology (including limiting densities) were identified. These densities, considered to be at least reasonably accurate, were used as standards and compared with other published densities. Most publishedn-fatty acid densities, judged by these criteria, appear to be reasonably accurate.     

Analysis of C18:1 cis and trans fatty acid isomers by the combination of gas-liquid chromatography of 4,4-dimethyloxazoline derivatives and methyl esters

Trans fatty acids in foods are usually analyzed by gas-liquid chromatography (GLC) of fatty acid methyl esters (FAME). However, this method may produce erroneously low values because of insufficient separation between cis and trans isomers. Separation can be optimized by preceding silver-ion thin-layer chromatography (Ag-TLC), but this is laborious. We have developed an efficient method for the separation of 18-carbon trans fatty acid isomers by combining GLC of FAME with GLC of fatty acid 4,4-dimethyloxazoline (DMOX) derivatives. We validated this method against conventional GLC of FAME, with and without preceding Ag-TLC. Fatty acid isomers were identified by comparison with standards, based on retention times and mass spectrometry. Analysis of DMOX derivatives allowed the 13t, 14t, and 15t isomers to be separated from the cis isomers. The combination of the GLC analyses of FAME and DMOX derivatives gave results comparable with those obtained by GLC of FAME after preceding Ag-TLC, while saving about 100 h of manpower per 25 samples. It allowed the identification and quantitation of 11 trans and 8 cis isomers and resulted in 25% higher values for total C_18:1 trans, compared with the analysis of FAME alone. The combination of DMOX and FAME analyses, as applied to the analysis of 14 foods that contained ruminant fat and partially hydrogenated vegetable and fish oils, indicated that the most common isomers were 11t in ruminant fats, 9t in partially hydrogenated fish fats, and either 9t or 10t in partially hydrogenated vegetable fats. The combination of GLC analyses of FAME and DMOX derivatives of fatty acids improves the quantitation of 18-carbon fatty acid isomers and may replace the laborious and time-consuming Ag-TLC.     

Variables affecting the yields of methyl esters derived from in situ esterification of rice bran oil

The influence of specific factors on in situ methanolic esterification of rice bran oil (RBO) using sulfuric acid catalyst was investigated. using high-FFA rice bran was found to be the most effective means to increase methyl ester yields. The ester content of the extract increased about 67% when the FFA content of oil was increased from 16.6 to 84.5%. Increasing the reaction time beyond 30 min did not affect yields. Increasing the temperature from 20 to 65°C elevated the FAME yield by about 30%, but increasing the amount of acid catalyst above 5 mL did not enhance yield, and increasing the methanol dose from 200 to 250 mL had a negligible effect.     

Supercritical carbon dioxide fractionation of fish oil fatty acid ethyl esters

Fractionation of fish oil fatty acid ethyl esters was investigated with the aim of obtaining a lipid fraction enriched in ω-3 fatty acids and with a suitable EPA/DHA ratio. The results obtained highlight the possibility of modifying the original fatty acid ethyl esters concentration by optimizing the extraction conditions in terms of pressure, temperature, and supercritical carbon dioxide flow rate. Supercritical fluid fractionation (SFF) appears to be a useful processing technique for changing the composition of lipids in order to obtain high value functional products. The use of proper fractionation temperatures and pressures along the column influenced the solvent-to-feed ratio to obtain fractions with suitable composition for market requirements.     

Adducts of cyclic acid anhydrides and fatty amines as anti-rust additives in water-based cutting fluids

A variety ofN-alkyl carboxylic acid amides was prepared from the reaction of cyclic dicarboxylic acid anhydrides and various amines, and screened for anti-rust properties and antimicrobial activity in spent coolants of water-based cutting fluids. The triethanol amine salts of the adducts of maleic anhydride with octylamine, decylamine, dodecylamine and oleylamine, and the one of phthalic anhydride with octylamine showed both good anti-rust and antimicrobial activity.     

In situ esterification of rice bran oil with methanol and ethanol

In situ esterifications of high-acidity rice bran oil with methanol and ethanol and with sulfuric acid as catalyst were investigated. In the esterification with methanol, all free fatty acids (FFA) dissolved in methanol were interesterified within 15 min, and it was possible to obtain nearly pure methyl esters. The amount of methyl esters obtained from a given rice bran was dependent on the FFA content of the rice bran oil. In the esterification with ethanol, it was not possible to obtain pure esters as in methanol esterification, because the solubilities of oil components in ethanol were much higher than those in methanol.     

Fast formation of high-purity methyl esters from vegetable oils

Experiments have confirmed that the base-catalyzed methanolysis of vegetable oils occurs much slower than butanolysis because of the two liquid phases initially present in the former reaction. For the same reason, second-order kinetics are not followed. The use of a cosolvent such as tetrahydrofuran or methyl tertiary butyl ether speeds up methanolysis considerably. However, like one-phase butanolysis, one-phase methanolysis initially exhibits a rapid formation of ester, but then slows drastically. Experiments show that the half-life of the hydroxide catalyst is too long to explain the sudden slowing of the reaction. Similarly, lower rate constants for the methylation of the mono- and diglycerides are not a reasonable explanation. Instead the cause has been identified as the fall in polarity which results from the mixing of the nonpolar oil with the methanol. This lowers the effectiveness of both hydroxide and alkoxide catalysts. Increasing the methanol/oil molar ratio to 27 in the one-phase system raises the polarity such that the methyl ester content of the ester product exceeds 99.4 wt% in 7 min. This has obvious implications for the size of new methyl ester plants as well as the capacity of existing facilities.     

Fast formation of high-purity methyl esters from vegetable oils

Experiments have confirmed that the base-catalyzed methanolysis of vegetable oils occurs much slower than butanolysis because of the two liquid phases initially present in the former reaction. For the same reason, second-order kinetics are not followed. The use of a cosolvent such as tetrahydrofuran or methyl tertiary butyl ether speeds up methanolysis considerably. However, like one-phase butanolysis, one-phase methanolysis initially exhibits a rapid formation of ester, but then slows drastically. Experiments show that the half-life of the hydroxide catalyst is too long to explain the sudden slowing of the reaction. Similarly, lower rate constants for the methylation of the mono- and diglycerides are not a reasonable explanation. Instead the cause has been identified as the fall in polarity which results from the mixing of the nonpolar oil with the methanol. This lowers the effectiveness of both hydroxide and alkoxide catalysts. Increasing the methanol/oil molar ratio to 27 in the one-phase system raises the polarity such that the methyl ester content of the ester product exceeds 99.4 wt% in 7 min. This has obvious implications for the size of new methyl ester plants as well as the capacity of existing facilities.     

Synthesis of β-bromoethoxylates and β-chloroethoxylates from olefinic fatty methyl esters

Olefinic fatty methyl esters [undec-10-enoate (1), octadec-Z-9-enoate (2), methyl-12 hydroxy octadec-Z-9-enoate (3)], on reaction with an N-halosuccinimide (4–5)—i.e., N-bromosuccinimide (NBS; 4) or N-chlorosuccinimide (NCS; 5)—in the presence of diols such as mono-, di-, tri-, and tetraethylene glycols (6–9), gave the respective β-bromo- or β-chloroethoxylates (11–34).     

Biotransformation of saturated monohydroxyl fatty acids to 2-tetrahydrofuranyl acetic acid derivatives: Mechanism of formations and the biological activity of 5-n-hexyl-tetrahydrofuran-2-acetic acid

Transformation of 12-hydroxyoctadecanoic acid (12-HOA) to 5-n-hexyl-tetrahydrofuran-2-acetic acid (5-HTFA) byBacillus lentus NRRL B-14864 (B-14864) was carried out in the presence or absence of oligomycin, 2-bromooctanoic acid (2-BA), or sodium azide. In addition, several saturated and monounsaturated monohydroxyfatty acids, saturated monooxofatty acids, and monounsaturated fatty acid were used as substrates for transformation reactions by B-14864 or corynebacterium FUI-2. Methyl esters of the transformation products were analyzed by gas chromatography and gas chromatography/mass spectroscopy. Various γ-lactones and tetrahydrofuran fatty acid derivatives were conversion products when saturated monohydroxyfatty acids were used as substrates; the production of 5-HTFA from 12-HOA by B-14864 cells was completely inhibited in the presence of high concentration of oligomycin, 2-BA, or sodium azide; and fatty acid β-oxidation metabolic intermediates, 6-hydroxydodecanoic, 4-oxododecanoic, and 4-oxodecanoic acids were products when 12-HOA, 10-oxo-, and 12-oxooctadecanoic acids were used as substrates. Our results suggest that the production of 5-HTFA from 12-HOA by B-14864 was through the fatty acid β-oxidation pathway. Three-day-old driedfruit beetle pupae were topically treated with 5-HTFA to test for juvenile hormone activity, and 5-HTFA was found to possess juvenile hormone-like activity in pure form but not when it was diluted to 10%. Presented in part at the 37th West Central States Biochemistry Conference Annual Meeting, Columbia, Missouri, Oct. 1994.