A process for making ethylene glycol by feeding reactants including 1,2-dioxygenated organic compounds, an organometallic homogeneous catalyst, and hydrogen to a hydrogenation reactor, reacting at least a portion of the reactants with hydrogen in the presence of the organometallic homogeneous catalyst to produce a reaction product mixture containing ethylene glycol, and passivating the catalyst by contacting the catalyst with a carbon monoxide to thereby suppress the formation of by-product diols other that the ethylene glycol primary product, and suppress the formation of by-product tetrols and by-product glycolaldehyde acetals; and separating at least a portion of the ethylene glycol from the reaction product mixture.