The potential energy surface for reactions of acyl iodides and acyl chlorides with methanol was studied by quantum-chemical methods. Stereoelectronic parameters of the prereaction bimolecular complexes and possible reaction products were examined. Transition states were localized for the transformation of prereaction complexes into final products. Dual reactivity of acyl iodides toward methanol was explained in terms of similar activation parameters found for the four-center and SN2 reaction mechanisms.