The Studies On Amine-promoted Benzene Oxidation Hydroxylation With Dioxygen

Hydroxylation of benzene is a very important organic reaction for the activation C-H bonds of unsaturated atoms and the production of important chemicals. Meanwhile, it is the one of the most issues to be studied in synthesis. Owning to the high energy of C-H bond in benzene ring, benzene can be hardly oxygenated by common oxidants. At present, more powerful oxidants such as N2O and H2O2 have been used in order to realize the oxidation of benzene. And the hydroxylation of benzene with dioxygen or air has become a research hot, because of molecular oxygen economically and environmentally favorable.Here, we reported a new method of direct hydroxylation of benzene to phenol with dioxygen in presence of amine based on the results gained by formers in our group on the benzene hydroxylation. A systematic study on the reaction characteristic and effect factors of benzene hydroxylation was carried out using a stainless steel autoclave designed and made by our group as a reactor. And the initial reaction mechanism was provided based on our experimental results.The contents of this thesis are presented as follows:1. Firstly, the methods and recent advances in the field of benzene hydroxylation were summarized, and the process and mechanism of benzene oxidation were discussed.2. A GC-MS qualitative analysis and RP-HPLC internal quantitatively analyze method were built, and the quantitatively analyze method was optimized and tested.3. The promoted effect of different organic amines on aerobic oxidation hydroxylation benzene and substituted benzenes was studied. The results showed, in general, aliphatic amines were better than aromatic amines and tertiary amines were better than secondary or primary amines. Meanwhile, triethylamine as an example, the autoxidation process of amines was studied.4. In order to further explore this process of benzene hydroxylation, amides, as the primary intermediate of amines oxidation, were synthesized and purified according to documented procedures and used to oxidation of benzene. The results showed that the contribution of amides to benzene hydroxylation was quite low.5. The effect of HAc and water on amine-promoted benzene oxidation hydroxylation with air was studied. The results showed that HAc had promotive effect and water had negative effect on the amine-promoted benzene hydroxylation system. 6. The effect ofα-H in the amine on the process of benzene oxidation was studied combined with the promoted effect of heteroatom compounds including N or O on benzene hydroxylation.7. A possible mechanism of hydroxyl radical presence on the new method of amine-promoted benzene oxidation hydroxylation with dioxygen was proposed based on our experimental results and combined with the discussion and test. Meanwhile, the mechanism was carried out initial test.