Synthesis of cineole from raw turpentine

Abstract

Cineole is one of monoterpene compounds usually produced from aromatic plants especially pine trees. It is mostly used for flavoring agent, aromatherapy, herbicide active compound, and pharmaceutical industry. Raw turpentine from pine tree has several derivatives, such as: α-pinene, β-pinene, limonene, δ-carene, camphene, terpineol, etc., with cineole being the component with the highest market price. However, there is no direct pathway to produce cineole from raw turpentine. Commonly, cineole presents as a side product from hydration of α-pinene or turpentine to terpineol and this process will not be economic. The distillation process to separate cineol from other components would be difficult and energy demanding because of its low concentration in the product. In this study, synthesis of cineole was conducted in a hope to obtain higher yield of cineole. The methods were managed in two reaction steps. First, the reaction of raw turpentine with water and acid catalysts to form terpineol for 3 hours at 85°C. Second, drawn off the water from the mixture then continue the reaction for 3 more hours at the same temperature to let terpineol isomerizes and becomes cineole. Based on the experimental results, it was found that using combined p-toluenesulfonic acid (PTSA) with several weak acids i.e. oxalic acid, citric acid, and formic acid, each at certain optimum composition, resulted 10.6% - 21.8% of cineole. These results are better than the previous generic process which cineole produced below 5%.