1.2- Diphenylethane radical cation

Carbon-Carbon Bond Cleavage in Radical Cations of Diphenylethane Derivatives... 

In this connection, it is interesting to compare the cation-radicals of 1,2-diphenyl- and 1,1,2,2-tetraphenylethanes in their ability to expel a proton or to cleave the exocyclic C-C bond. The former cation-radical preferentially reacts by deprotonation (Camaioni and Franz 1984, Baciocchi et al. 1986). The C-C bond strength of 121.5 kJ moC in 1,2-diphenylethane cation-radical is too high. At the same time, the C-C scission induced by electron transfer is only feasible if the strength of this bond is lesser than 42 kJ mol In the case of 1,1,2,2-tetraphenylethane cation-radical, this magnitude is equal to 38 kJ mol only, and the C-C scission indeed takes place (Arnold and Lamont 1989). 

The quenching of - -t by 1-methylpyrrole in nonpolar solvents results in the formation of a fluorescent exciplex, but no adduct formation (117). Irradiation in acetonitrile (anhydrous or aqueous) solution produces 1,2,3,4-tetraphenylbutane (65) in low yield. Formation of adducts 75 and 76 and 1,2-diphenylethane (64) is observed upon irradiation in acetic acid solution and attributed to protonation of t-lT followed by coupling of the 1,2-diphenylethyl radical and 1-methylpyrrole cation radical and deprotonation of the coupling product ... 

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