For stabilized triphenylphosphonium keto ester ylides acyl stretching frequencies of the anti ester group from HF/6-31G (d) calculations fit experimental values with Scale Factor, SF= 0.866, as estimated earlier for the diester ylides, but Scale Factor= 0.834 has to be used to fit data for the syn-keto group and for syn–anti diketo ylides. The DFT functional BLYP/6-31G (d), with the literature Scale Factor= 0.9945, generally gives good fits for both keto ester ...