AbstractHydrogen 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.