Preparation of isobutyric acid and esters

Claim 1

In the process for the carbonylation of propylene by contacting the propylene and carbon monoxide with water or a lower alkanol of 1 to 4 carbon atoms in the presence of solvent and a palladium catalyst in complex with a ligand, the improvement which comprises using as said ligand an ortho-substituted ligand of the formula P Ar 3 wherein each Ar is independently selected from ##STR4## and wherein the Ar moieties bear a total of one or two substituents in positions ortho to one or two carbon-phosphorus bonds, the substituents being selected from the group consisting of lower alkyl of 1-4 carbon atoms, lower alkoxy and phenyl, and wherein the Ar groups each contain up to three substituents in positions meta or para to a carbon-phosphorus bond and selected from the group consisting of lower alkyl, lower alkoxy, chloride, fluoride, hydroxyl and carboxyl and provided that when Ar is ##STR5## one or two of the Ar moieties can each bear one substituent selected from phenoxy and a fused aromatic hydrocarbon ring at an ortho position to form 1-naphthyl, and provided further that when the substituent is a fused aromatic hydrocarbon ring, each such Ar moiety can bear one additional substituent at a second ortho position selected from alkyl of 1-4 carbon atoms, alkoxy and phenyl.