John Rafelt

Recent advances in the partial oxidation of organic molecules using heterogeneous catalysis

With increasing environmental legislation, the synthesis of catalysts that can be easily recovered, give high selectivity and produce low levels of waste is highly desirable. Immobilising an active species on a support material can ease the separation from a reaction, allowing the material to be used again. A constant goal for the selective oxidation of organic substrates is the design of new and improved heterogeneous catalysts. Recent highlights of research towards this goal are reviewed.

The use of Reichardt's dye as an indicator of surface polarity

Reichardts dye can be used to determine the surface characteristics of a range of inorganic and organic materials. This simple, rapid technique gives information regarding the polarity of the surface.

Catalytic oxidation of alkyl aromatics using a novel silica supported Schiff base complex

A new heterogeneous catalyst based on a chemically modified mesoporous silica gel and possessing immobilised chromium ions has been prepared and successfully applied to the aerial oxidation of alkyl aromatics at atmospheric pressure and in the absence of solvent.

Environmentally friendly liquid phase oxidation : enhanced selectivity in the aerial oxidation of alkyl aromatics, epoxidations and the Baeyer-Villiger oxidation using novel silica supported transition metal ions

Active transition metal species (Co, Cu, Cr, Ni or Mn) supported on a chemically modified silica gel are used as heterogeneous catalysts in a range of liquid phase oxidation reactions: alkyl aromatic side chain oxidations, epoxidations of alkenes and Baeyer–Villiger oxidations of linear ketones to esters and cyclic ketones to lactones. The catalyst employs metal centres bound to the silica surface via a hydrophobic spacer chain and is thus chemically robust and has a relatively high loading for a supported reagent (c 0.4 mmol g−1). The Cr version of the catalyst promotes the oxidation of ethylbenzene to acetophenone in a solvent-free system at a rate of 5.5% h−1 (>370 turnover h−1). It is also active for the oxidation of p-chlorotoluene and p-xylene to p-chlorobenzoic acid and p-toluic acid respectively. Cyclohexene is converted to its oxide at room temperature at a rate of c 28% h−1 (c 12 turnover h−1) using either the Ni or Cu versions of the catalyst. The room temperature Baeyer–Villiger oxidation of cyclohexanone is achieved at a rate of 44% h−1 (49 turnover h−1) using the Ni-containing catalyst. The same material also promotes the Baeyer–Villiger oxidation of linear aliphatic ketones and aromatic side chains. All the above systems use either air or molecular oxygen as the oxidant rather than peroxides or peracids. © 1999 Society of Chemical Industry

Liquid phase oxidations using novel surface functionalised silica supported metal catalysts

Metal species supported on a surface functionalised silica gel are active heterogeneous catalysts for the liquid phase, room temperature epoxidation of cyclohexene and the aerobic oxidation of ethylbenzene.

Self-assembly of novel supramolecular networks formed by 1-[(1-propyl)iminomethyl]-2,4-dihydroxybenzene

The condensation of propylamine and 2,4-dihydroxybenzaldehyde in absolute ethanol leads to the formation of a unique supramolecular structure, whose crystal structure is reported here. The material displays an unusual synergistic combination of intra- and intermolecular hydrogen bonding.