carbonic acid esters are important compounds as a gasoline extender , an octane number improver , an organic solvent and a reacting agent in place of phosgene for production of isocyanates , polycarbonates and various intermediates of agricultural chemicals and pharmaceuticals . according to the present invention , carbonic acid esters can be prepared by reacting an alcohol with carbon monoxide and oxygen in the presence of a catalyst comprising a copper halide and a tertiary organophosphorus compound having phenyl group or alkyl group .