Analysis of the gas‐phase addition of water to formaldehyde: A semiempirical and ab initio study of bifunctional catalysis by H 2 O

Semiempirical AM1, MNDO‐PM3, and MNDO/M, as well as ab initio Hartree–Fock and Möller–Plesset calculations using the 4‐31G, 6‐31G(d,p), and 6‐31 +G(d,p) basis sets have been done on the water‐assisted addition of water to formaldehyde. ab initio methods predict a reduction of 30% of the bimolecular Δ G 0,‡ (from 48 to 33 kcal/mol) when an ancillary water molecule is used as catalyst. AM1 and MNDO‐PM3 predict anticatalysis instead; Δ G 0,‡ for the termolecular addition is larger than the one for the bimolecular reaction. MNDO/M predicts a modest decrease, from 42 to 39 kcal/mol. We conclude that, as predicted by the ab initio calculations, there is a bifunctional catalysis caused by the ancillary water. Two of the semiempirical methods are qualitatively (and all of them quatitatively) in disagreement with this conclusion. © 1992 by John Wiley & Sons, Inc.