Comparative thermolysis of beta-and alpha-pinenes in supercritical ethanol:the reaction characterization and enantiomeric ratios of products

摘要

The thermolysis of p-pinene and the co-thermolysis of an equimolar mixture of beta-and alpha-pinenes in supercritical ethanol were carried out.The reaction of beta-pinene affords p-myrcene as the major product (>70%).Considerable differences in the temperature dependence of the reaction rate were revealed for the transformations of beta-pinene into p-myrcene and of a-pinene into limonene.The pre-exponential factors and the activation energies were calculated.The enantiomeric ratios of the thermolysis products of beta-and a-pinenes and limonene were estimated.The starting monoterpenes do not undergo racemization during thermolysis.The thermolysis of enantiomerically pure a-pinene affords racemic (±)-limonene,whereas (-)-p-pinene gives (-)-limonene.The enantiomeric ratio in the latter remains equal to the enantiomeric purity of the starting p-pinene.