Study on Thermal Isomerization of Isopimaric Acid

The thermal isomerization reaction of isopimaric acid was studied by a treatment at different temperature of 250 °C, 260 °C and 270 °C for 1-5 h under the protection of nitrogen. The isomerization mechanism of isopimaric acid was illuminated. Isopimaric acid was remarkably isomerized to 8, 15-isopimaric acid and sandaracopimaric acid, the higher thermal treatment temperature combined with longer thermal treatment time, the faster isomerization rate of isopimaric acid was observed. It was found that the isomerization rate of isopimaric acid towards 8, 15-isopimaric acid was faster than to sandaracopimaric acid. The decomposition reaction of pimaric-type acids occurred slightly in conditions of 250 ~ 270 °C.