PURPOSE: A quinoid compound is added to the reaction system and the reaction between an alcohol, carbon monoxide and oxygen is carried out in the presence of a copper compound or a combination of a copper compound with a platinum compound to produce a carbonate ester advantageously with largely reduced carbon dioxide as a by-product.

CONSTITUTION: Carbon monoxide and oxygen are fed batchwise or continuously to the reaction system which is composed of a copper compound or a combination thereor with a platimum-group compound, preferably a palladium compound, and an alcohol, to which a quinoid or a compound convertible into a quinoid compound under the reaction conditions, to effect the reaction at a pressure of 100 or less atmosphric pressure, 20W250°C, preferably 50W200°C whereby a carbonate ester is obtained. The amount of the quinoid added ranges from 0.1W5wt% based on the total weight of the reaction mixture.