Stereoelectronic source of the anomalous stability of bis-peroxides

The unusual stability of bis- and tris-peroxides contradicts the conventional wisdom – some of them can melt without decomposition at temperatures exceeding 100 °C. In this work, we disclose a stabilizing stereoelectronic effect that two peroxide groups can exert on each other. This stabilization originates from strong anomeric n_O → σ*_CO interactions that are absent in mono-peroxides but reintroduced in molecules where two peroxide moieties are separated by a CH₂ group. Furthermore, such effects can be induced by other σ-acceptors and amplified by structural constraints imposed by cyclic and bicyclic frameworks.