Ab initio molecular dynamics study of the reaction of water with formaldehyde in sulfuric acid solution

Ab initio molecular dynamics methods have been used to study the reaction mechanism of acid-catalyzed addition of water to formaldehyde in a model system of an aqueous solution of sulfuric acid. Using the method of constraints
we find that an H2O molecule can be added to formaldehyde by a controlled transfer of a catalytic proton from a hydronium ion in acid solution to the carbonyl oxygen. The CO bond formation occurs at a stage midway in the
proton transfer process. The process can be reversed by removing the H+ from the protonated product diol, leading
to CO bond breaking at approximately the same stage of proton transfer. This state is a combined transition state for protonation and addition, suggesting that the kinetics of these two steps in the acid-catalyzed reaction is concerted.