most preferred co catalysts are ruthenium compounds preferably the co catalysts are chloride free such as acetates the carbonylation catalyst is used in an amount preferably within the range of 0 0001 to 10 and more preferably within the range of 0 001 to 1 of the total weight of the reaction medium preferably the carbonylation is performed in the presence of a catalyst promoter preferably the catalyst promoter is an iodide more preferably the catalyst promoter is an alkyl iodide most preferably the catalyst promoter is methyl iodide preferably the concentration of methyl iodide is from about 0 6 wt to about 36 wt based on the total weight of the reaction medium more preferably the concentration of methyl iodide is from about 4 wt to about 24 wt most preferably the concentration of methyl iodide is from about 6 wt to about 20 wt preferably the reaction is performed in the presence of a catalyst stabilizer suitable catalyst stabilizers include those known to the industry in general there are two types of catalyst stabilizers the first type of catalyst stabilizer is metal iodide salt such as lithium iodide the second type of catalyst stabilizer is a non salt stabilizer preferred non salt stabilizers are pentavalent group va oxides see u s pat no 5 817 869 phosphine oxides are more preferred triphenylphosphine oxides are most preferred the catalyst stabilizer is present in a molar ratio of stabilizer catalyst preferably within a range of 1 1 to 5000 1 more preferably within the range of 60 1 to 5000 1 and most preferably within the range of 60 1 to 500 1 optionally.