J. B. Brown

Solubilities of the fatty acids in organic solvents at low temperatures

SummaryA considerable series of pure fatty acids has been prepared and their solubilities have been determined at temperatures down to −70° in acetone, methanol and Skellysolve B. Solubility ratios have also been determined for oleic to palmitic acid and linoleic to oleic acid in a number of additional solvents at certain temperatures.

Low temperature solubilities of fatty acids in selected organic solvents

SummaryA number of highly purified fatty acids have been prepared and their solubilities determined in six common organic solvents within the temperature range from 10° to −70°. The acids studied were palmitic, stearic, oleic, elaidic, petroselinic, petroselaidic, linoleic, stearolic, arachidic, eicosenoic, behenic, erucic, and brassidic. The solvents used were methanol, ethyl acetate, diethyl ether, acetone, toluene, and n-heptane, representing six different solvent types. A limited study was also made with a series of hydrocarbon solvents in order to note any effects of solvent structure on fatty acid solubility. Data are discussed with respect to their application in separating various fatty acid mixtures by low temperature crystallization.

A study of the tetrabromide method of estimating linoleic acid in fatty acid mixtures

Summary1.When linoleic acid is brominated in cold petroleum ether, the yield of insoluble tetrabromides is empirical; it is affected by the composition of the petroleum ether and by the amounts of linoleic acid and of other fatty acids which may be in a given mixture.2.The tetrabromide number of pure linoleic acid ranges from 103.7 when a 2-gram sample is brominated to practically zero with 10 mg. of the acid.3.Data are presented describing the tetrabromide yields of linoleic acid alone and in various mixtures with oleic acid, when brominated at the 2.0-, 1.0-, and 0.5-g. levels of sample. From these data curves can be drawn by which it is possible to ascertain by interpolation the per cent of linoleic acid in a mixture.4.Seventeen concentrates of linoleic acid from corn oil, safflower oil, and butter fat have been assayed from the curves, and the results compared with values calculated from the iodine number.5.Several linoleic acid concentrates from corn oil were shown to contain appreciable amounts of isomeric dienoic acids.6.Examination of two linoleic acid concentrates from butter fat shows for the first time the indubitable presence of linoleic acid in this fat.

The composition of coffee oil and its component fatty acids

SummaryA specimen of coffee oil has been examined with the objective of determining its composition in the light of possible uses of the oil which is recoverable as a byproduct in the soluble coffee industry. The oil, as obtained by extraction of the coffee grounds with solvent, contains over 5% of unique unsaponifiable material which, without preliminary removal, makes the oil unsuitable for many purposes. It has been shown that the unsaponifiable and glyceridic components can be separated by molecular distillation.A specimen of the methyl esters of the fatty acids of the oil was examined by the ester distillation fractional crystallization techniques. The composition of the component fatty acids has been calculated. The oil contains 46% of linoleic acid. Saturated and unsaturated acids of the C20, C22, and C24 series are present in coffee oil in small amounts.

Preparation and purity of linoleic acid from commercial corn, cottonseed, and safflower oils

Linoleic acid from commercial corn, cottonseed, and safflower oils was prepared by low temperature crystallization using acetone and petroleum ether as solvents; temperatures ranged between −70 and 50C. This method has the advantages of simple equipment and of flexibility in preparatory capacity. The crystalline fraction obtained at −55C was shown to be “pure” linoleic acid.Isomerization with potassium tertiary butoxide, oxidative cleavage by periodate-permanganate, and analysis by liquid-liquid and gas-liquid partition chromatography were used to ascertain the purity and the presence of isomers in the final product. This fraction was found to contain 90 to 95%, 9,12 dienoic acid; approximately 5% of dienes with the first double bond at the C8 position and the second bond either at the C12 or C13 positions; and small amounts of nonconjugatable 9,15cis,cis dienes. Linoleic acid from these oils was similar in composition, except that from corn oil showed the presence of diene with the first double bond at the C11 position.

Syntheses of cis- and trans-7- and 8-octadecenoic acids: Comparison of the properties of cis- and trans-6-, 7-, 8-, 9-, and 11-octadecenoic acids

Summary1. The cis- and trans-modifications of 7-, 8-, and 11-octadecenoic acids were synthesized by methods which leave no doubt as to their structure.2. Many new compounds have been reported including 7-octadecynoic acid, 8-octadecynoic acid. 7,8-diketostearic acid, 8,9-diketostearic acid, cis- and trans-7-octadecenoic acids and their 7,8-dihydroxystearic acid derivatives, and cis- and trans-8-octadecenoic acid derivatives and their 8,9-dihydroxystearic acid derivatives.3. A new series of intermediate reaction products has been reported although these compounds were not fully characterized. These compounds include hexamethylene bromochloride, hexamethylene iodochloride, 1-chloro-6-heptadecyne, and 1-chloro-7-heptadecyne.4. The extinction coefficients at 10.36 microns of the cis and trans-6-, 7-, 8-, 9-, and 11-octadecenoic acids have been calculated and compared.5. The melting points of the cis- and trans-octadecenoic acids and their dihydroxy derivatives were shown to exhibit alternating patterns.

Isomerization of Linoleic, Linolenic, and Other Polyunsaturated Acids with Potassium Tertiary Butoxide and Its Application in the Spectrophotometric Estimation of These Acids

SummaryIt has been shown that potassium tertiary butoxide isomerizes such unsaturated fatty acids as linoleic, linolenic, arachidonic, and pentaenoic at a temperature of 90°. With 5% potassium-t-butanol reagent conjugation of linoleic acid attains a maximum at the end of 2 hrs. and remains steady thereafter even up to 10 hrs. while with linolenic, arachidonic, and pentaenoic acids it is still occurring at the end of such long times of reaction as 48 and 10 hrs., respectively. This continuance of reaction at the end of such long periods with these higher unsaturated acids demonstrates that the isomerization with the tertiary butoxide reagent at 90° is not complicated by side reactions, such as polymerization and deisomerization. All the methods studied give high absorption coefficients in the lower regions of maxima—233 mµ with linolenic, 233 mµ and 268 mµ with arachidonic acids—showing thereby that isomerizations of these acids occur stepwise. Based on this study, a method using 5% potassium-t-butanol as reagent, at 90° with a time of reaction of 4 hrs., has been proposed for the estimation of linoleic and linolenic acids. The k233 value for linoleic acid (94.0) obtained by this method compares very well with those by the 6.6% KOH-glycol and 21% KOH-glycol methods while with linolenic acid the k233 value (63.2) is higher and k268 value (74.2) lies intermediate between those by the other methods. The proposed method is shown to estimate the linoleic and linolenic acid contents of several typical oils with about the same degree of accuracy as either the 6.6% KOH-glycol or 21% KOH-glycol methods.Appendix. When this paper was ready to be submitted, a note (27) describing the use of tertiary butoxide reagent on the kinetic study of isomerization of linoleic and linolenic acids came to our attention. Extinction coefficients at 235 mµ and 268 mµ are reported for linolenic acid and the values (61.4, 74.2) obtained by isomerization with a molar solution of the reagent at 99.5° and 180 minutes’ time of reaction are about the same order as those reported in this paper. It is of interest to note that these authors have also noted that no destruction of the product occurs at this temperature and time of heating.

The preparation of stearolic acid and methyl dideutero-oleate, and certain of their derivatives

Summary1. Improved methods of synthesizing stearolic acid and 9,10-diketostearic acid in high yields are described. Dehydrobromination of dibromostearic acid by sodamide in ammonia is shown to be a very smooth and practical reaction.2. Dibromo-oleic acid, methyl stearolate, and ethyl stearolate have been prepared and characterized.3. Stearolamide, dibromo-oleyl alcohol, and stearolyl alcohol (9-octadecynol-1) have been synthesized and their properties described.4. Selective hydrogenation and low temperature crystallization have been utilized to prepare oleic acid from stearolic acid and methyl oleate and methyl 9,10-dideutero-oleate, free of other higher unsaturated substances, from methyl stearolate.5. Complete reduction of dideutero-oleate yielded 9,10-tetradeuterostearate which, on hydrolysis, gave tetradeuterostearic acid.6. Infra-red absorption curves for 9,10-dideuterooleate, tetradeuterostearate, and tetradeuterostearic acid are also reported.

Octadecadienoic acids of shortenings and margarines

SummaryA scheme is described to separate the fatty acids of shortenings and margarines into four fractions, the final filtrate of which contains most of the polyunsaturated acids. The nature of the unsaturated acids in these fractions is discussed. It is observed that these fats contain 25–40% oftrans monoethenoic acids and 2–8% of linoleic acid and considerable proportions of both 9,12-cis, trans ortrans,cis and isolatedcis,trans isomers of linoleic acid.

Autoxidation of methyl oleate, methyl stearolate, and methyl 9,10-dieuteroöleate

SummaryA comparative study of the autoxidation of methyl oleate, methyl 9,10-dideuteroöleate, methyl stearolate, and stearolic acid has re-emphasized the complexity of the autoxidation phenomenon. The autoxidation of the acetylenic compounds indicates the importance of peroxidation of the active methylene group as compared to the addition of oxygen at the unsaturated linkages. The importance of olefinic hydrogens and the role of the double bond with respect to the induction periods and possible addition reactions has been brought out by the studies on the autoxidation of the deuteroöleate. Consequently it appears that during autoxidation of methyl oleate, oxidative attack is initiated at the olefinic position and then at α-methylenic position and that water formation occurs shortly thereafter. At least some of the hydrogen of the water formed during autoxidation comes from the olefinic hydrogens.It appears that most of the non-aqueous volatile cleavage products arising from a rupture of a carbon to carbon bond are peroxidic in character. The nature of these volatile peroxides appears different from several commercially available organic peroxides since they are capable of oxidizing methyl oleate in a manner to yield the high melting form of dihydroxystearic acid whereas peracids and some peroxides under similar conditions give only the low melting isomer.