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Synthesis of triglyceride estolides from lesquerella and castor oils
Author(s) -
Isbell Terry A.,
Cermak Steven C.
Publication year - 2002
Publication title -
journal of the american oil chemists' society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.512
H-Index - 117
eISSN - 1558-9331
pISSN - 0003-021X
DOI - 10.1007/s11746-002-0632-1
Subject(s) - chemistry , castor oil , oleic acid , dehydration , catalysis , organic chemistry , nuclear chemistry , polymer chemistry , biochemistry
Triglyceride (TG) estolides were synthesized from the hydroxy moieties of lesquerella and castor oils with oleic acid. Complete esterification of the hydroxy oils was possible when a slight excess of oleic acid was employed (1 to 1.5 mole equivalents). The estolides could be formed in the absence of catalyst at 175 to 250°C under vacuum or a nitrogen atmosphere. The optimal reaction conditions were found to be under vacuum at 200°C for 12 h for lesquerella and 24 h for castor oil. The lesquerella esterification reaction was completed in half the time of the for castor and with lower equivalents of oleic acid due to the difunctional hydroxy nature of lesquerella TG compared to the trifunctional nature of castor TG. Interesterification or dehydration of the resulting estolides to conjugated FA was not a significant side reaction, with only a slight amount of dehydration occurring at the highest temperature studied, 250°C. Use of a mineral‐or Lewis‐acid catalyst increased the rate of TG‐estolide formation at 75°C but resulted in the formation of a dark oil, and the reaction did not go to completion in 24 h. Estolide numbers (i.e., degree of estolide formation) for the reaction and characterization of the products were made by 1 H NMR and 13 C NMR. The decrease in the hydroxy methine signal at 3.55 ppm was used to quantify the degree of esterification by comparing this integral to the integral of the alpha methylene protons on the glycerine at 4.28 and 4.13 ppm.