L. Matachowski

The effect of peripheral substituents in metalloporphyrins on their catalytic activity in Lyons system

Manganese porphyrin catalysts with different number of halogens atoms substituted at the phenyl and pyrrole rings were investigated in the Lyons system in oxidation of cyclooctane with molecular oxygen (as air) to cyclooctanone and cyclooctanol without the use of sacrificial co-reductant. The catalytic activity of metalloporphyrins increases with the increase of the redox potential of metalloporphyrins in the investigated system and shows almost linear relationship with the number of the halogens on porphyrin macrocycle. On the basis of obtained results the new reaction mechanism is discussed and proposed.

Manganese porphyrins as catalysts for oxidation of cyclooctane in Lyons system

Abstract Oxidation of cyclooctane with molecular oxygen (as air) in the presence of first generation manganese porphyrins XMn III (TTP), where X=F − , Cl − , Br − , I − , OH − , CH 3 COO − , as catalysts was investigated in the Lyons system. The catalytic activities of the metalloporphyrins in the oxidation of cyclooctane to cyclooctanone and cyclooctanol are covariant with electronegativity of halides as axial ligands and increase with the decrease of the redox potential of metalloporphyrins. It was concluded that axial ligands are involved in the reaction initiating the reaction by generating the radicals with simultaneous reduction of the manganese porphyrin. Relatively high yields of products were obtained without the use of sacrificial co-reductant.

Ethylene oxidation over lead(II) oxide

Abstract A search has been made for the centre of the catalytic epoxidation of ethylene over thin films of PbO. A square of surface oxygen ions is possibly the centre of epoxidation on silver. Similar units are present on 001 PbO. Experiments have shown that on PbO ethylene can be converted to ethylene oxide. Selectivity to ethylene oxide was low, most of the ethylene being converted to CO and CO 2 . Possible mechanisms for the oxidation are discussed.