Abstract: Esters or carboxylic acids are prepared from olefins containing at least two carbon atoms by reacting the olefin with carbon monoxide in the presence of:(i) a first complex of a selected Lewis acid with the ester or carboxylic acid, whichever is the reaction product recovered;(ii) a second complex of the Lewis acid with an alcohol, if an ester is being prepared, or with water, if a carboxylic acid is being prepared; and(iii) a metal carbonyl compound containing a Group IB transition metal in the first oxidation state; andby recovering the reaction product(s).The preferred olefin is propylene, the preferred ester to be prepared is methylisobutyrate, the preferred metal is copper and the preferred Lewis acid is boron trifluoride.