Narrow Results

The study of haemin-catalysed oxidation reactions was extended to substituted aromatic rings. Both electron-donating and electron-withdrawing substituents on aromatic rings act as para- and meta-directing agents in the presence of tetrakis(2,6-dichlorophenyl)porphyrin iron(III) chloride as catalyst and m-chloroperbenzoic acid as oxidant. A new kinetic method for measuring relative rates of epoxidation of alkenes and related compounds has been developed; while steric hindrance results in decreasing the rate of hydroxylation, electron-rich and electron-withdrawing substituents were found to increase the rate of hydroxylation. A linear relationship between the logarithm of the relative rate of hydroxylation and σ Hammet is obtained, although electron-donating and electron-withdrawing substituents fit separate lines. Addition of pyridine to haemin was shown to increase the yield of epoxidation but decrease the yield of aromatic hydroxylation.

The selective oxidation of sulfides with hydrogen peroxide to give sulfoxides was carried out in aqueous solution by water-soluble manganese porphyrin as mimics of cytochrome P450-like catalyst. Different factors that influencing the selective oxidation of sulfides, for example, catalyst, amount of catalyst, solvent and reaction temperature were investigated. MnTE4PyP (meso-tetrakis(N-ethylpyridinium-4-yl) manganese porphyrin) was efficient and selective catalyst for oxidation of various sulfides. The reaction showed first-order dependence in both [sulfide] and [H₂O₂], and a fractional order respect to catalyst. Oxygen atom transfer mechanism involves high-valence intermediate was proposed, which was supported by kinetic orders and spectrophotometric evidences.