Thermal polymerization of unsaturated fatty esters normal methyl linoleate

Abstract

Summary 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. 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°. Polymerization of mixtures of normal and conjugated linoleate indicate that dimer may be formed by their reaction with each other. 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. 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.

Isomers of linoleic acid. Infrared and ultraviolet properties of methyl esters

“…The ester of the yon Mikusch acid (VI) showed only one very strong band at 988 cm -I. This compound is undoubtedly trans-10, trans-12 linoleate, according to Nichols et al (12) and yon Mikusch (18). The 988 cm -1 band is therefore characteristic of trans-trans conjugated linoleates, and one would predict that the Mangold acid, trans-9, trans-11 (6,18) would show the same band at 988 cm -1.…”

“…Since naturally occurring linoleic acid is cis-cis, the present findings are not of great importance in spectral analyses of linoleic acid in natural oils. However in a study of the thermal polymerization of methyl linoleate (12) it was found that recovered monomer (distilled from the polymerized mixture) contained as much as 20% of a material which did not analyze as either conjugated tinoleate or normal linoleate by and the ordinary spectral methods. It was noted that this material must be largely an isomeric linoleate (particularly in the monomers from the earlier stages of reaction) judging from the iodine values.…”

Fractional vacuum distillation of herring oil methyl esters

“…50 losses of highly unsaturated acids were very high and that they were proportional to the chain length and degree of unsaturation. This fact has of course been pointed out earlier by many authors (8,(19)(20)(21)(22), but the degree of thermal and oxidative decomposition and polymerization that can be expected in a vacuum distillation on a pilot plant scale has not to our knowledge been followed in detail before. Only 17% of docosahexaenoic acid (22:6) present was recovered in the distillate, whereas the recovery of most of the major constituent saturated and monounsaturated acids was close to 100%.…”

Application of high vacuum fractional distillation to complex mixtures of methyl esters of polyunsaturated fatty acids

“…The structures of artifacts of fractional distillation have not received a great deal of attention. However, with the formation of polymers as evidenced by a nondistillable residue in the still-pot at the end of the distillation, the formation of conjugated (18,19) and cyclic compounds (13,14,]6) may also be formed on the basis of the theories of polymerization (21,22). These compounds may be distilled because they are monomeric and thus distillate fractions that have elevated values for trans unsaturation or diene conjugation, or both, as well as spurious peaks in GLC analysis may be considered to contain artifacts.…”