Decomposition of Hydroperoxides derived from Terpinolene and α-Pinene under Various Conditions

Abstract

The following work was undertaken in order to clarify the products and mechanism of decomposition of hydroperoxides (HPO) derived from terpinolene and a-pinene under various conditions. These HPO were prepared by reactions of terpinolene or a-pinene with oxygen in the presence of benzoylperoxide at 10-600C, and used as decomposition samples without removing the unreacted terpenes. For both HPO, thermal decomposition, and decomposition by reagents such as ferrous ammonium sulfate, sulfu;ic acid, perchloric acid, potassium hydroxide and potassium permanganate have been examined. Moreover, HPO from a-pinene has been decomposed in the presence of heavy rnetal salts such as Mn-, Fe-, Co-, Ni-, Cu-, Znand Pb-stearate as a catalyzer. Each reaction was carried out below 1000C. After removing the reagents or the catalyzers, the reaction products were fractionated in vacuo and identified by means of chemical methods and infra-red absorption spectrum. In the case of decomposition by heat or ferrous ammonium sulfate, HPO yields mainly piperitenone and P-mentha-1, 4(8)-dien-e-ol for terpinolene and verbenone and trans-verbenol for a-pinene respectively. When sulfuric acid or perchloric acid was used the major products were these ketones for each HPO. In the alkaline decomposition of both HPO each alcohol above described was formed exclusively. These results show that the decomposition of these HPO proceeds through radical in the first case, cationic in the second and anionic intermediate in the third. The fact that the acid catalyzed decomposition gives a small amount of organic acid, indicates that opening of cyclohexene ring pqrtly takes place. The behaviour of the decomposition by potassium permanganate was cornplex and not clear, ・ In the decomposition of HPO of a-pinene catalyzed by the heavy metal salts, the products were similar to those in the thermal decomposition. The catalytic eMciency of these heavy metal salts on the decomposition of HPO derived from ec-pinene decreases in the order: Co>Mn > Pb>Ni > Fe, Cu, Zn and this result is in well accordance with that of the decomposition of cyclohexane HPO catalyzed by laurinate of heavy metal obtained by Pritzkowi).