Ab initio calculations analyze the interaction between dimethyl ether and hydroperoxy radical, and closed-shell analogues HOOH and OOH−. The two minima on each surface contain more than one H-bond. The more strongly bound structure contains a OH⋯O bond, along with blue-shifting CH⋯O; the other minimum contains exclusively CH⋯O. The strongest complex occurs with the anionic OOH−, followed by OOH and then HOOH. Alterations of the covalent bond lengths, vibrational frequency shifts and electronic charge shifts are associated with strengths of individual H-bonds. The data help explain how the H-bonds are affected by the open-shell character of the OOH radical.