First step of formose or Butlerov reaction involves C–C bond formation between two formaldehyde molecules resulting in glycolaldehyde. This reaction happens under basic conditions in solution. A tandem mass spectrometry investigation of dissociation of deprotonated glycolaldehyde in the gas phase, to study the formose reaction in a retro-synthetic point of view, has been reported. In the present work, we have carried out electronic structure theory calculations and quasi-classical direct chemical dynamics simulations to model the gas phase dissociation of the conjugate base of glycolaldehyde. The dynamics simulations were performed on-the-fly using the hybrid density functional B3LYP theory with the 6-31+G∗ basis set under collision induced dissociation (CID) conditions. Trajectories were launched with two different deprotonated forms of glycolaldehyde for a range of collision energies mimicking experiments. Reverse formose reaction was observed primarily from the slightly higher energy isomer via a non-statistical pathway. Intramolecular hydrogen transfer was ubiquitous in the trajectories. Simulation results were compared with experiments and detailed atomic level dissociation mechanisms are presented. © 2020 Elsevier B.V.