Abstract: Three series of fossil model compounds were synthesized and their oxidation and reduction potentials were determined by CVusing BAS-100Belectrochemical analyzer.Thermodynamic cycles have been developed to determine the enthalpies of the carbon─oxygen bond cleavage of the derived radical ions.It was found that the carbon─oxygen bond is similarly activated in a thermodynamic sense by introducing an electron to the system as what was observed previously in a structurally similar radical cation, except smaller in amplitude.The carbon─oxygen bond cleavages of radical ions are all exothermic or slightly endothermic, implying a low barrier for rupture of the sessile bond,This is important to fossil fuel industry for improving traditional coal gasification routine and selecting new fragmentation path.Correlation analysis shows that plots of △H_eleav[C─O]^·+vs.( △BDE─△E_ox[C─O]) and △H_eleav[C─O]^·+vs.( △E_red[C─O]+△pK_a[HA]) are linear.Bond properties in relation to their structural features for both radical ions and their parent molecules are discussed and are compared with the relevant bond energy data in literature.

Key words: Radical anion, Radical cation, Bond cleavage energy, Activation of carbon─oxygen bond