Leitão EFV, Angelo Fonseca de Souza M, do Monte SA, Ventura E. Competition between electron transfer and base-induced elimination mechanisms in the gas-phase reactions of superoxide with alkyl hydroperoxides.
Phys Chem Chem Phys 2021;
23:5583-5595. [PMID:
33655284 DOI:
10.1039/d0cp05761d]
[Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Understanding the mechanism responsible for peroxides decomposition is essential to explain several biochemical processes. The mechanisms of the intrinsic reactions between the superoxide radical anion (O2˙-) and methyl, ethyl, and tert-butyl hydroperoxides (ROOH, with R = Me, Et, and t-Bu) have been characterized to understand the mechanism responsible for peroxides decomposition. The reaction energy diagrams suggest a competition between the spin-allowed and spin-forbidden electron transfer (ET), and base-induced elimination (ECO2) mechanisms. In all cases, the spin-allowed ET mechanism describes formation of the ozonide anion radical (O3˙-), either complexed with an alcohol molecule or separated. For the O2˙-/MeOOH(EtOOH) reactions, HCO2- (MeCO2-) + H2O + HO˙ and OH- + CH2O(MeCHO) + HO2˙ products are associated with the spin-forbidden ET and ECO2 channels, respectively. On the other hand, for the reaction between O2˙- and t-BuOOH, the spin-forbidden ET route describes formation of the MeCOCH2- enolate (either separated or hydrated) along with the methyl peroxyl (MeO2˙) radical. In addition, the regeneration of O2˙-via spin-forbidden ET and ECO2 channels was also characterized from the decomposition of ROOH, yielding diols (CH2(OH)2 and MeCH(OH)2), aldehydes (CH2O and MeCHO), and oxirane (cyc-CH2CMe2O).
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