Processes for the production of acetic acid by carbonylation of methanol and reactive derivatives thereof in a liquid phase reaction medium, wherein the reaction medium comprises a finite amount of water, a homogeneous catalyst, an alkyl halide promoter, and a catalyst stabilizer/co-promoter comprising an imidazolium cation R1R2Im+ as an iodide salt, wherein R1 and R2 are each independently a substituted or unsubstituted alkyl or cycloalkyl, with the proviso that R1 and R2 are not the same.