The early steps of the Formose Reaction are studied computationally using DFT methods. It was found that the dimerization of Formaldehyde takes place via an intramolecular deprotonation reaction, involving the calcium catalyst, and leads to Glycolaldehyde, a critical intermediate in the process.

Abstract

In this work, the initial steps of the mechanism of the Formose reaction (FR) is computationally studied using DFT methods. The FR has been considered to be a relevant process in the prebiotic evolution leading to several types of sugars or carbohydrates. These molecules are some of the basic building blocks of the life. The dimerization of formaldehyde was found to take place via an intramolecular deprotonation reaction, leading to the formation of an intermediate which, after an isomerization, forms a Ca-complex of the cis-enediol tautomer of glycolaldehyde. The aldol reaction of this complex with additional formaldehyde gave glyceraldehyde, the simplest aldotriose. The catalyst Ca(OH)₂ plays a dual role in the reaction, acting as a base (in the intramolecular deprotonation) and as Lewis acid (activating the carbonyl group) in the aldol addition.