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  • Title: Superoxide radical anion adduct of 5,5-dimethyl-1-pyrroline N-oxide. 5. Thermodynamics and kinetics of unimolecular decomposition.
    Author: Villamena FA.
    Journal: J Phys Chem A; 2009 Jun 04; 113(22):6398-403. PubMed ID: 19425559.
    Abstract:
    The unimolecular decomposition of the superoxide radical anion adducts of 5,5-dimethyl-1-pyrroline N-oxide (DMPO), 5-carbamoyl-5-methyl-1-pyrroline N-oxide (AMPO), 5-ethoxycarbonyl-5-methyl-1-pyrroline N-oxide (EMPO), and 5-diethoxyphosphoryl-5-methyl-1-pyrroline N-oxide (DEPMPO) were computationally investigated by using PCM/BHandLYP/6-311G(d,p)//B3LYP/6-31G(d) and PCM/ROMP2/cc-PVDZ//B3LYP/6-31G(d) levels of theory. Results indicate that the O-O bond scission for nitrone-O(2)H to form the hydroxyl radical and the biradical is endoergic, and that the ring-opening step to form the nitrosoaldehyde is highly exoergic. The energy barriers for the O-O bond scission and ring-opening processes indicate that the former is the rate-limiting step of the reaction. The overall energetics for DMPO-O(2)H decomposition in the presence and absence of explicit water interactions was found to be the most preferred; however, no significant differences in the energetics of decomposition among the various isomers of AMPO-O(2)H, EMPO-O(2)H, and DEPMPO-O(2)H were observed.
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