In this study we revisit one of the simplest reactions: the self-reaction of the ethene-derived hydroxyperoxy radical formed via sequential addition of ˙OH and O₂ to ethene. Previous studies of this reaction suggested that the branching to ‘accretion products’, compounds containing the carbon backbone of both reactants, was minimal. Here, CF₃O⁻ GC-CIMS is used to quantify the yields of ethylene glycol, glycolaldehyde, a hydroxy hydroperoxide produced from , and a C₄O₄H₁₀ accretion product. These experiments were performed in an environmental chamber at 993 hPa and 294 K. We provide evidence that the accretion product is likely dihydroxy diethyl peroxide (HOC₂H₄OOC₂H₄OH 00000000 00000000 00000000 00000000 11111111 00000000 11111111 00000000 00000000 00000000 ROOR) and forms in the gas-phase with a branching fraction of 23 ± 5%. We suggest a new channel in the chemistry leading directly to the formation of (together with glycolaldehyde and an alkoxy radical). Finally, by varying the ratio of the formation rate of and in our chamber, we constrain the ratio of the rate coefficient for the reaction of to that of and find that this ratio is 0.22 ± 0.07, consistent with previous flash photolysis studies.