COMPUTER-AIDED MECHANISM ELUCIDATION OF ACETYLENE HYDROCARBOXYLATION TO ACRYLIC-ACID BASED ON A NOVEL UNION OF EMPIRICAL AND FORMAL METHODS

In the elucidation of complex multistep reactions, it is easy to overl ook significant mechanistic hypotheses. Hence, the use of computer pro grams to search for mechanisms is attractive, but these programs must respect the prior knowledge held by the investigator. Virtually all kn owledge-based programs accommodate prior knowledge of either what can or what cannot happen, but there are advantages in exploiting both typ es of knowledge simultaneously. We report a novel alliance of two prog rams that enables these advantages and which represents an advance in the capabilities of computational chemistry, as illustrated here on th e complex synthesis of acrylic acid from acetylene, CO, and water cata lyzed by palladium complexes. The pathways reported by the programs we re categorized as hydride, hydroxycarbonyl (alcoholate-like), and meta llocyclic, the mechanistic types that are known from publications on h ydrocarboxylation and hydrocarbalkoxylation of unsaturated molecules i n solutions of transition metal complexes. Many specific pathways were not considered before in the absence of comprehensive computerized se arches.