Toluene radical cation value

Direct esr evidence for the intermediacy of radical-cations was obtained on flowing solutions of Co(III) acetate and a variety of substituted benzenes and polynuclear aromatics together in glacial acetic acid or trifluoroacetic acid solution . A p value of —2.4 was reported for a series of toluenes but addition of chloride ions, which greatly accelerated the reaction rate, resulted in p falling to —1.35. Only trace quantities of -CH2OAC adducts were obtained and benzyl acetate is the chief product from toluene, in conformity with the equation given above. 

Radical cations of weak acids may react either by heterolytic cleavage (loss of a proton to produce a radical) or homolytic cleavage (loss of a hydrogen atom to form a carbocation). In a polar solvent heterolytic cleavage is usually favored because of the favorable solvation energy of the proton, and radical cations are ordinarily much more acidic than the corresponding neutral compounds. For example, the pfC value of toluene in DMSO is 43, while the pfC " value for the radical cation of toluene is —20. Therefore, the difference in pK values of toluene and its radical cation is 63. 

Aryl and aliphatic amines are perhaps the best known D molecules primarily due to the availability of the nonbonded electrons on nitrogen for PET processes. The simplest bond cleavage reaction for amine cation-radicals is heterolytic C—H cleavage or deprotonation. It is well known that the acidity of protons on a species after loss of an electron, i.e., after one-electron oxidation, is greatly enhanced [7]. For example, the pKa of the benzylic protons in the toluene cation-radical have been estimated to be —10 [7] compared to pKa value of 35 before oxidation. The process of proton loss can be extremely fast, on the time scale of picoseconds [8]. 

---