Experimental formation of hydroxyacetone (HA) from glycerol over La2CuO4 catalyst under mild experimental conditions (533 K, N2 atmosphere) was correlated with molecular modeling results with the aim to propose reaction pathways. Based on these results, a novel mechanism in terms of elementary reactions is proposed for gaseous phase process. The results suggest that there are two main routes that contribute to HA formation. The main and more feasible reaction pathway corresponds to the direct 1,2-dehydration of glycerol. The second pathway involves the dehydrogenation of glycerol to produce glyceraldehyde, which is then dehydrated toward HA through the formation of a six-membered cyclic transition state during the hydrogenation step. Finally, the pyruvaldehyde formation pathway was found to be a parallel reaction to the HA formation which could be displaced by tuning the reaction conditions. HA formation as a result of pyruvaldehyde hydrogenation was also proposed, but it was found to be a less important route.