Possible reactions of GO, GA, and EG with H atoms. The straight lines represent H-atom-addition reactions, while the dotted lines represent H-atom-abstraction reactions. The reactions denoted by colored lines have been observed experimentally. The figure only displays the species formed through one or two H-atom reactions of GO, GA, or EG to enhance clarity. Hydroxyketene, ketene, 1,2-ethenediol, vinyl alcohol, and acetaldehyde are denoted as HK, KE, ED, VA, and AA, respectively. CB₁ and CB₂ refer to carbenes. Additionally, R₅, HK and KE are shown twice in the figure for better transparency.