R. F. Paschke

Cis, Trans Isomerism of the Eleostearate Isomers

SummaryThe cis, trans isomers of the conjugated trienes present a difficult problem for complete determination of structure.Several methods of attack have been outlined, and application of two of them have been made to α and β eleostearic acids, α and β licanic acids, and to pseudoeleostearic acid.These results indicate the following structures: α eleostearic: cis-9, trans-11, trans-13 β eleostearic: trans-9, trans-11, trans-13 pseudoeleostearic: trans-10, trans-12, trans-14 α licanic: 4-keto, cis-9, trans-11, trans-13 β licanic: 4-keto, trans-9, trans-11, trans-13

Evidence for hydroperoxide formation in the autoxidation of methyl linolenate

Summary1. The results of chemical, spectral, and distillation analyses on the isolated oxidized fractions of three samples of methyl linolenate autoxidized at 0°C. to peroxide values from 600 to 760 m.e./kg. indicated that about 60% of the products consisted of cis,transconjugated diene methyl octadecatrienoate-monohy-droperoxide.2. A product was isolated from the reduced peroxide concentrates which consisted of about 90% cis,trans- conjugated diene methyl monohydroxyoctadecatrienoate.3. Analytical micromolecular distillation analyses showed that the total oxidized material isolated from samples of autoxidized methyl linolenate contained only about 15% polymeric material under the conditions of autoxidation employed in this study.4. Linolenate was shown to be similar to linoleate in forming a cis,trans-conjugated monomeric monohydroperoxide as a major initial product of autoxidation at 0°C.

Dimer acid structures. the thermal dimer of methyl 10-trans, 12-trans, linoleate

Thermal dimerization of the conjugated 10-trans, 12-trans linoleate (250C, 5 hr) produced a dimer whose structure is shown to be that of the Diels-Alder reaction between two molecules of monomer, with one molecule acting as diene, and either one of the two double bonds of the second molecule acting as dieneophile. This produces four skeletal isomers of a tetrasubstituted (1,2,3,4) cyclohexene structure with α-β unsaturation on one chain. The isomers formed depend on whether the 10 or the 12 double bond acts as dieneophile, and whether the monomers add “head to head” or “head to tail.” Evidences for the structures include chemical analyses, ozonolysis, nuclear magnetic resonance, IR and UV spectrometry and particularly mass spectrometry of the distilled dimer, of the completely hydrogenated dimer, and of the aromatized dimer formed by catalytic dehydrogenation. The hydrogenated dimer can be separated into two components by TLC. These are probably related to “head to head” vs. “head to tail” addition.

Thermal polymerization of unsaturated fatty esters normal methyl linoleate

Summary1.Debromination methyl linoleate has been polymerized at 290° and 300° for varying periods, and analysis has been made for monomer, dimer, trimer, normal, and conjugated linoleate.2.The disappearance of normal linoleate follows a first order reaction rate with values of K=0.10 hr.−1 at 300° and 0.05 hr.−1 at 290°.3.Polymerization of mixtures of normal and conjugated linoleate indicate that dimer may be formed by their reaction with each other.4.The value for K, the first order reaction velocity constant for disappearance of normal linoleate, decreases to a limiting value on dilution with methyl stearate. This limiting value is about one-fourth that obtained on undiluted linoleate.5.The above facts are qualitatively explained by assuming that the mechanism of dimerization of normal linoleate is extensively: N»C relatively slow N+C→D relatively rapid.

The Unsaturated Fatty Acids of the Alga Chlorella

HE purpose of this paper is to elucidate further the composition of the unsaturated fatty acids of the fresh water alga Chlorella pyrenoidosa grown in pure culture in pilot plant quantities. In 1948 Milner (1) had shown the effect of certain environmental conditions on the yield of Chlorella and its lipid content. An excellent discussion of these results and the economic aspects of the problem appeared in 1951 (2) in this journal. Significant to us was the observation that the cell yield increased with increased nitrogen content of nutrient media but that the cells thus obtained had a low content of fatty acid. These however were highly unsaturated as indicated by iodine numbers of over 160. Restriction of nitrogen in the media gave poor yield of C hlorella, but the fatty acid content of the cells increased tenfold to over 60%. Iodine number of the fatty acids dropped to 125. The one sample which we examined was the low-lipid, high-iodine number type. The sample was obtained from Arthur D. Little Inc. Pilot plant studies at the laboratory were apparently aimed at high cell and high protein yields. Milner found that the fatty acids were almost all of C~s and C~s chain length, tte noted that the iodine number of the C~6 fraction indicated at least 17% of triene fatty acids. Polyunsaturated C~6 fatty acids are relatively rare. Heyes and Sborland (3) have re

Dimer acid structures. The dehydro-dimer from methyl oleate and Di-t-butyl peroxide

The dehydro-dimer of methyl oleate was prepared and its structure determined as a model of a non-ring dimer for reference in studying the structure of other fatty dimer acids.The dehydro-dimer of methyl oleate is formed by the action of di-t-butyl peroxide on methyl oleate. The reaction is stoichiometric; one mole of DTBP producing one mole of dehydrodimer and two moles of t-BuOH, when excess methyl oleate is used. The dimer was shown to contain two double bonds, and to be formed by carbon-to-carbon linkages predominantly and equally at the 8, 9, 10 and 11 carbons of the oleate monomer segments.Unsaturation was determined by quantitative hydrogenation and far UV absorption. The points of linkage were established by diagnosis of the positions of the involved tertiary carbons of the hydrogenated dimer 1) by chemical oxidation, and 2) by mass spectrometry. Positions of the double bonds were determined by quantitative ozonization, reductive cleavage followed by gas chromatography of the aldehydes and aldehyde esters. Precise molecular weight of the hydrogenated dimer was determined from the parant mass peak at the expected m/e of 594, confirming the non-ring structure. The unhydrogenated dimer showed a parent m/e peak at the expected value of 590.The bridging at the 8 and 10 positions is explained as being due to coupling of radicals with limiting resonance structures resulting from loss of a hydrogen atom from the methylene at position 8. The bridging at the 9 and 11 positions is explained as due to coupling of limiting resonance structures resulting from loss of a hydrogen atom from the methylene at position 11.Mass spectrometric data indicate that the dimerization is a coupling of the expected free radical forms, rather than attack by an oleate free radical on the double bond of an intact oleate molecule, with subsequent loss of hydrogen to form the second double bond in the dimer.Coupling at the 2-position (α to COOCH3) occurs in not more than 5–10% of the molecules. A small amount of cyclic dimer may be present.

Inter- and intramolecular polymerization in heat-bodied linseed oil

Summary1. Linseed oil has been polymerized at 300° for 1.5, 3, and 6 hours. The polymeric glycerides have been separated from the monomeric glycerides, and the derived methyl esters of each fraction have been analyzed for monomer, dimer, and trimer.2. The monomeric glycerides show very little intradimerization, ranging from 1.3 to 6% of their acid groups, or 3 to 4% of the total polymeric acid groups in the whole oil.3. The polymeric glycerides show appreciable intradimerization, from 10 to 20% of their total polymeric acid groups.4. There is no evidence that a shift from intra- to interdimerization is the major cause of the sudden increase in viscosity in the later stages of thermal polymerization.5. The rapid rise in viscosity is due to the nature of the relationship of viscosity to molecular weight and of molecular weight to extent of reaction in the difunctional polymerization system present.

Thermal polymerization of methyl linolenate, alpha- and beta-eleostearates

SummaryThe rates of polymerization of alpha and beta eleostearates agree with second order kinetics, as would be expected for a bimolecular Diels-Alder addition. The all-trans, beta isomer reacts faster than thecis, trans, trans alpha isomer, in agreement with knowncis, trans effects on diene activity.The polymerization of normal linoleate follows an apparent first order reaction. It is suggested that conjugation is the slow rate determining monomolecular reaction, as has been proposed for the non-conjugated linoleate isomers.

The aromatization of linoleic acid with palladium catalyst

SummaryHydrogen transfer catalysts are known to promote the elaidinization and conjugation of unsaturated fatty acid derivatives. More extensive reactions were indicated when palladium was tried as a polymerization catalyst. A subsequent study showed that methyl linoleate could be readily cyclized and aromatized in the presence of palladium.Methyl linoleate was heated in an evacuated ampule for 6 hrs. at 270°C. with 5% of a 10% palladium on charcoal. The iodine value was lowered to 43.9 and the apparent linoleate content to less than 2%. The products were separated by urea segregation and distillation. They consisted of approximately 7% polymer, 18% methyl stearate, 40% monoolefins, and 30% of a methyl ester of an aromatic fatty acid (handling loss 5%). The aromatic material was readily oxidized to orthophthalic acid.The mechanism by which aromatics, mono-olefins, and saturates are produced through cyclization and hydrogen transfer is not known, but possible routes are suggested.

Methyl punicate,Alpha andBeta eleostearate.Cis, trans isomerism and structure

Methyl esters ofbeta eleostearic,alpha eleostearic, and punicic acids have been isomerized with iodine and light to the same equilibrium mixture of 64%beta, 33%alpha, and 2.6% punicate structures. The course of isomerization is in agreement with the following structures:trans, trans, trans forbeta; cis, trans, trans foralpha; andcis, trans, cis for punicate, in agreement with structures provenvia synthesis by Crombie and Jackson. There is some theoretical and experimental evidence that the center double bond of this type of conjugated triene isomerizes less readily than the outer double bonds.