AbstractThe strength of the H‐O bond in H−O2should be a good indicator of the chemical reactivity of superoxide, O−2, as a hydrogen atom abstractor. This quantity can be calculated if the electron affinity of HO2is known. A recent experimental determination of the electron affinity of HO2[V. M. Bierbaum, R. J. Schmitt and C. H. DePuy,J. Am. Chem. Soc.,103, 6262–6263 (1981)] gave that value as 27.4 ± 0.2 kcal mol−1. The H‐O bond energy of HO−−2can then be calculated from that value to be approximately 66 kcal mol−1. Various theoretical methods may also be used to approximate the value of the electron affinity of HO2. These methods generally give values in accord with the experimental result. Based on the low H—O bond energy of 66 kcal mol−1for HO−2, superoxide is expected to be relatively unreactive, comparable to iodine atoms but less reactive than bromine atoms or HO2and much less reactive than chlorine atoms or hydroxyl radicals. Based on our analysis, we predict that superoxide can only react as a hydrogen atom abstractor with substrates that contain relatively weak bonds to hydrogen such as hydrox
展开▼
