Application Of Ionic Compounds-supported Catalysts In The Oxidation Of Cyclohexene

Cyclohexene with an unsaturated C=C double bond and someα-H atoms, can be used as substrate in the oxidation and the reaction place on C=C double bond for epoxidation orα-H atom for allylic oxidation. Due to the poor selectivity in the oxidation of cyclohexene, it needs an efficient system for oxidation of cyclohexene for both academia and industry. Molecular oxygen, being the cheapest and cleanest oxidant, however, could not react with substrates directly. In fact, molecular oxygen must be activated firstly by appropriate catalysts. Hence, the development of the high active and selective catalysts is the key for molecular oxygen oxidation.We designed and synthesized the copper-Salen catalysts modified by ionic compounds. The most appealing features of the catalysts were that the cation of ionic salt connected with the metal center by conjugated double bond and the anion interacted with the cation through hydrogen bond, thus the cation-anion interaction could easily deliver to the metal center. The catalysts were used in the allylic oxidation of cyclohexene, and the oxidation reaction conditions were optimized. We also studied the influences on the catalytic activity of catalysts modified by ionic compounds.In this dissertation, the performances of ionic salt-supported catalysts in different situations on the oxidation of cyclohexne were explored. The results showed that the catalytic activities of these modified catalysts were significantly improved compared with their unmodified counterpart and their selectivity did not lose. Low polarity solvent could improve the activity, however, considering the reaction rate, we used acetonitrile as reaction solvent. Modifying catalysts by ionic salts can improve the catalyst reactivity more significantly by axial ligand, and catalysts modified by ionic compounds could conveniently reused for its excellent thermal stability. Later on, the influences on the catalyst reactivity of the ionic salts-supported catalysts by changing nature of ionic compounds were explored. We found that the anions significantly improved the activity, due to that the cation of ionic salt connected with the metal center by conjugated double bond and the anion interacted with the cation through hydrogen bond, thus the cation-anion interaction could easily deliver to the metal center. The ionic salt-supported catalyst Cu-[Salen-Py][PF₆^-] with the most nucleophilical anion showed the highest catalyst reactivity. The different polarity solvent could change cation-anion interaction in Cu-[Salen-Py][X^-], which could influent on the catalytic activity. The ionic compound can be contacted or separated ion pairs in different solvents. It prefers to be contacted ion pairs in low polarity solvent whereas separated in high polarity solvent. Therefore, the low polarity solvent could improve the catalytic activity.In short, the oxidation of cylohexene by oxygen was studied, and the novel catalysts modified by ionic compounds were involved. The characteristics of designed and micro-structure of ionic compounds could be used to improve the catalytic activity. This pronounced correlation between microstructure and macroscopic properties of ionic compounds may enlighten us to design novel and efficient types of task-specific catalysts to improve the oxidation reaction.