| The oxidation of saturated C-H bond is an important technical method to obtain oxygenous organic compounds. With the development of petroleum chemical industry, many oxidation technologies have been applied triumphantly. For example, cyclohexane can be oxidized into a mixture of cyclohexanol and cyclohexanone, p-xylene to terephthalic acid and the toluene to benzoic acid and so on. In addition, the oxidation of the side chain on alkybenzene is a promising route to get ketone product.Arocmatic ketones as an important material are mainly gained from the Friedel-Crafts acylation of arene in chimecal industry. During the Friedel-Crafts acylation of arene, much acidic waste water was produced from the hydrolys of AlCl3, which caused the harm to the environment. With the development of the oxidation technologies, saturated C-H bond can be oxidized with high conversion and excellent selectivity. More and more attention has been paid to the oxidation of the side chain on the ethylbenzene and its derivatives. A typical example is the oxidation of ethylbenzene to prepare acetophenone. Furthermore, p-nitroacetophenone and p-diacetylbenzene which can not be obtained through the Friedel-Crafts acylation reaction owing to electron-withdrawing substituent on the phenyl ring. On the contrary, they can be easily prepared by the oxidation of the corresponding alkylbenzene.Cytochromes P-450 as an enzyme can catalyze the oxidation of saturated C-H bond with high conversion and excellent selectivity under mild condition. The active site of cytochromes P-450 is iron porphyrin. In recent years, many metalloporphyrins were synthesized to catalyze the oxidation reaction. Encouraged by these achievements, in this thesis, 12 transitional metalloporphyrins were synthesized in order to mimic the oxidation function of cytochromes P-450. The activation of molecular oxygen and oxidation of the side chain of ethylbenzene or its derivatives catalyzed by these complexes without additive was investigated. The results showed that the higher reduction potential the metalporphyrin has the better catalytic activity. In our case. (5, 10, 15, 20)-tetrakis(pentaflurophenyl)porphyrin cobalt(II) (14) with the highest reduction potential exhibited the highest catalytic activity. Under the optimal conditions (1×10-3 mol/L of 14, 1.5 MPa of O2, 100℃, 24 h), the conversion of ethylbenzene was 38.6%, the selectivity of acetophenone and 1-phenylethynol was 94.0% and 6.0% respectively. It was the best result in the literature. The electron-donating groups on the phenyl ring and the longer side chain on the alkylbenzene decreased the conversion, on the contrary, the electron-withdrawing substituent on the phenyl ring enhanced the conversion.The side chain oxidation reaction of ethylbenzene with molecular oxygen catalyzed by 14 was investigated by UV-Vis spectra. The intermediate specie with signal at 435 nm was further confirmed by 1H NMR to be [TPFPPCo(Ⅲ)]OH. Therefore, it can be deduced that the mechanism of the ethylbenzene oxidation with molecular oxygen catalyzed by 14 is analogous with the oxidation of alkane catalyzed by cytochromes P-450. Firstly, TPFPPCo(Ⅱ) and molecular oxygen generate TPFPPCoOO·species, then the oxidation reaction of ethylbenzene works according to two kinds of mechanisms, i.e. the metal-based mechnism and the radical chain mechanism. During the reaction, TPFPPCo(Ⅲ)O(Ⅲ)CoTPFPP precipitated from the reaction mixture by condensation of two molecular [TPFPPCo(Ⅲ)]OH. The low catalytic activity was assumed to be the catalyst deactivation by the formation ofμ-O dimer complex.The stimulation of K2Cr2O7 for the side chain oxidation of ethylbenzene with molecular oxygen catalyzed by 14 has been investigated. Under the optimal conditions (K2Cr2O7:ethylbenzene = 1:800, 1×10-3 mol/L of 14, 1.5 MPa of O2, 100℃, 24 h), the conversion of ethylbenzene was 55.2%, and the selectivity for acetophenone was 92.4%, better than 14 alone. Experimental results show that the function of K2Cr2O7 is not the promotion of the formation of catalytic species, but accelerating the decomposition of the peroxide.In order to compare their catalytic performance with metalloporphyrins, we synthesized 2,6-bis[(1-phenylimino)ethyl]pyridine dichloride cobalt(Ⅱ) (22),2,6-bis[(1-phenylimino)ethyl]pyridine dichloride manganese(Ⅱ) (23) and bis{2,6-di[(1-phenylimino)ethyl]pyridine}cobalt(Ⅱ) tetrachlorocobaltate (24). The single crystal X-ray structures of these complexes showed that the core metal atom is ligated by three N atoms from ligand in complex 22 and 23, located in a distorted trigonal bypyramidal geometry with the three N atoms and the core metal atom being coplanar. The complex 24 was formed by disproportion from 22 in CH2Cl2. The X-raystructure of complex 24 showed a octahedral geometry in which the Co(Ⅱ) atom is coordinated by six N atoms from two ligands. The side chain oxidation of ethylbenzene with molecular oxygen catalyzed by these complexes in the absence of any additives was also investigated, where Co complex (22) showed the highest catalytic activity. Under the optimal conditions (1.5×10-3 mol/L of 22, 1.0 MPa of O2, 120℃, 20 h), the conversion of ethylbenzene was 37.8%, and the selectivity for acetophenone and 1-phenylethynol was 82.5% and 13.5% respectively. The catalytic activity of Mn complex (23) was inferior to its Cobalt counterpart 22. The complex 24 had exihibited the lowest catalytic activity because the Co atom was coordinated six N atoms.
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