WHY IS IT INTERESTING TO STUDY CYCLOHEXANE OXIDATION

Cyclohexane oxidation was studied both under industrial conditions and using the Gif(IV) and the GoAgg(II) systems under ambient conditions. Under both conditions cyclohexylhydroperoxide is formed as a reaction intermediate. Using a passivated reactor and a stabilizer, cyclohexylhydroperoxide can easily be obtained in a concentration of 7% under industrial conditions. Its decomposition at 80-100-degrees-C is highly selective and the cyclohexanone:cyclohexanol ratio can be varied between 4:1 and 1:3, by the use of different transition metal catalysts. Its utilization for epoxidation, however, is much more interesting. The Gif(IV) system forms mainly cyclohexanone with very good turnover numbers but it is limited as it needs large quantities of zinc and forms coupling products with the pyridine used as a solvent. The GoAgg(II) system is much more appropriate as it is homogeneous and does not form any side products. The addition of picolinic acid strongly accelerates the reaction and the oxidized products can be accumulated to a concentration similar to that obtained in the industrial process. on the other hand, the catalyst deactivates rapidly by the formation of iron (hydr)oxide particles and the turnover numbers are low. A solvent system has to be found which avoids the hydrolysis of the catalyst while maintaining the high selectivity and the efficiency of the process.o TEXTO COMPLETO DESTE ARTIGO, ESTARÁ DISPONÍVEL À PARTIR DE AGOSTO DE 2015.1071371