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Synthesis of δ‐eicosanolactone and δ‐docosanolactone directly from meadowfoam oil
Author(s) -
Isbell Terry A.,
Cermak Steven C.
Publication year - 2001
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/s11746-001-0297-9
Subject(s) - perchloric acid , lactone , chemistry , sulfuric acid , yield (engineering) , solvent , organic chemistry , distillation , stoichiometry , materials science , metallurgy
δ‐Eicosanolactone and δ‐docosanolactone were synthesized directly from the triacylglycerides of meadowfoam ( Limnanthes ) oil. Perchloric and sulfuric acids were used in stoichiometric quantities (0.5–4.0 mol equiv) to cyclize triglyceride to δ‐lactone. When the reactions were run in the absence of solvent at 40°C, δ‐lactone yields ranged from 17–75% where δ/γ ratios ranged from 6∶1 to 10.4.∶1. Sulfuric and perchloric acids gave similar yields for their individually optimized reactions. Perchloric acid‐catalyzed reactions required less acid to produce similar amounts of δ‐lactone (HClO 4 at 2.0 mol equiv gave 73% yield vs. H 2 SO 4 , which gave 75% yield at 2.5 mol equiv). The use of polar nonparticipating solvents during the reaction had little impact on δ‐lactone formation or δ/γ ratio. Higher perchoric acid concentrations provided higher δ‐lactone yields with δ/γ ratios remaining nearly constant. The effect of sulfuric acid on δ‐lactone yield and δ/γ ratio was more direct; higher acid concentration improved, both. Both crystallization and short path distillation improved δ‐lactone quality but short path distillation gave, higher recovered yields. The δ‐lactones were converted to their corresponding 5‐hydroxy acids in the same reaction vessel, separated, and cyclized back to δ‐lactones upon heating under vacuum. This provided a convenient method for δ‐lactone purification.