The specific rates of reaction of several aliphatic radicals with Co(NH3)63+ and Ru(NH3)63+ were determined. Radicals on the α carbon relative to OH or NH2 groups were shown to be stronger reducing agents than radicals on the α carbon to a carboxylic or an amide group. The reactivity of the radicals ĊH2OH, CH3-ĊHOH, (CH3)2ĊOH, CH3ĊOHCOO–, and CH3COĊ(O–)CH3, toward Ru(NH3)63+ increases along this series, whereas the reversed order of reactivities is found for the reactions with Co(NH3)63+ and Cuaq2+. This order is different from the order of reactivities toward nitrobenzene and 2,3-butanedione where the reactivity increases along the series CH3ĊOHCO2–, ĊH2OH, CH3ĊHOH, and (CH3)2ĊOH. The latter order is identical with that of increasing pK of the OH group. The results are interpreted as suggesting that the contribution of π character to the orbital containing the unpaired electron in the radical significantly affects the specific rates of reactions. The implication of the results in radiobiology is discussed.
ASJC Scopus subject areas
- Chemistry (all)
- Colloid and Surface Chemistry