.Soybean oil triglycerides (SOT) can be used for the synthesis of rigid polymers. This research investigates the potential of using dense (sub/supercritical) CO2 in the reaction medium for the addition of functional groups to SOT. As an alternative and novel method, the reaction of SOT with KMnO4 in the presence of water and dense CO2 is presented. Dense CO2 is utilized to bring the soybean oil and aqueous KMnO4 solution into contact. Experiments are done at 10, 25, 34.5, 50 oC and 2.5, 5, 7, 11, 16MPa. Effects of temperature, pressure, NaHCO3 addition, and KMnO4 amount on the conversion (depletion by bond opening) of soybean-triglyceride double bonds (STDB) are investigated. The highest STDB conversions, about 40%, are obtained at the near-critical conditions of CO2. The addition of NaHCO3 enhances the conversion; one mole of NaHCO3 per mole of KMnO4 gives the highest benefit. Increasing KMnO4 up to 10% increases the conversion of STDB.