Isomerization of α-pinene oxide: solvent effects, kinetics and thermodynamics

Kinetics and thermodynamics of α-pinene oxide isomerization was investigated both theoretically and experimentally in different solvents in the temperature range of 50–140 °C using different zeolites, iron modified zeolites, Fe–H–MCM-41 and micro-mesoporous ZSM-5 derived catalysts. The aim was to elucidate the effect of solvent basicity and polarity on the product distribution in this reaction giving as the main value-added products campholenic aldehyde and trans-carveol, which are used as fragrances and perfumes. A generic kinetic first order model was developed composed of both parallel and consecutive routes. A thermodynamic analysis showed that product selectivity is determined by kinetic control and not by thermodynamics. Formation of campholenic aldehyde was favored in non-polar solvents, whereas basic solvents promoted formation of trans-carveol independent on temperature.