Nucleophilic addition of hydrogen sulfide to methyl oleate, methyl linoleate, and soybean oil

Hydrogen sulfide was added to methyl oleate, methyl linoleate, and soybean oil at −70 and 25 C in the presence of boron trifluoride. Major reaction compounds were identified by gas liquid chromatography and mass spectrometry. At −70 C with a 200 molar ratio of hydrogen sulfide to ester, the reactions were complete in 4 hr. Primary reaction product from methyl oleate was methyl 9(10)-mercaptostearate. Methyl linoleate gave ca. equal amounts of methyl 9-(2-pentyl-1-thiolan-5-yl) nonanoate and methyl 8-(2-hexyl-1-thiolan-5-yl) octanoate. At 25 C, the reaction of methyl oleate and linoleate with hydrogen sulfide was less complete, and more side reactions were noted. When equimolar amounts of methyl oleate and methyl 9(10)-mercaptostearate were reacted in the presence of boron trifluoride at 25 C, a new compound was formed, bis(methyl n-octadecanoate 9[10]-yl) sulfide. The addition of liquid hydrogen sulfide to soybean oil at −70 C in the presence of boron trifluoride yields a product which, upon saponification, acidification, and methylation analyzes by gas liquid chromatography as ca. 52% thiolan, 27% mercaptostearate, 10% palmitate, 6% stearate, and 5% unidentified compounds.