Benzene derivatives, pulse radiolysis

Aromatic radical-cations are generated by pulse-radiolysis of benzene derivatives in aqueous solution. Radiolysis generates solvated electrons, protons and hydroxyl radicals. The electrons are converted by reaction with peroxydisulpbate ion to form sulphate radical-anion, which is an oxidising species, and sulphate. In another proceedure, electrons and protons react with dissolved nitrous oxide to form hydroxyl radicals and water, Hydroxyl radicals are then made to react with either thallium(i) or silver(i) to generate thallium(ii) or silver(ll) which are powerfully... 

Okamoto K, Kozawa T, Saeki A, Yoshida Y, Tagawa S. (2007) Subpicosecond pulse radiolysis in liquid methyl-substituted benzene derivatives. Radiat Phys Chem 76 818-826. 

The effect of heavy atoms on the relative yields of fluorescence and phosphorescence has been investigated both by inserting Br and I substituents in the ring of deuterioporphyrin IX and its Zn derivative,340 and by adding ethyl iodide to the solution of a number of free base porphyrins.341 Other authors discuss the luminescence of protoporphyrin IX dimethylester after pulse radiolysis in benzene,848 and from monomeric and dimeric ethylenediamine-substituted protoporphyrin IX and some metal derivatives.343 Several reports consider the emission from porphyrins in Shpolskii matrices and other crystalline organic hosts.344-340... 

The technique has been described in detail elsewhere. [26] In short, a pulse of high energy electrons induces a series of chemical reactions that can be monitored, e.g., using time resolved UV-vis spectroscopy. The reaction of interest is usually induced by a reaction between a radical formed from radiolysis of the solvent (usually water) and a solute molecule. The primary radiolysis products in aqueous solution are HO, e q", H, HjOj, H2 and The major radical species, HO and e q, are formed in equimolar concentrations, 0.28 ol/J each, on electron or y-irradiation.[27] As can be seen in reaction 2, the hydroxyl radical does not yield a benzene radical cation instantly upon reaction with a substituted benzene. For this reason, secondary oxidants, such as S04, Brj and N3, are usually used to generate benzene radical cations. To determine one-electron reduction potentials of radical cations, the redox equilibrium between the radical cation of interest and a redox couple with a known one-electron reduction potential is studied. The equilibrium constant can be derived from the rate constants of the electron-transfer reaction and the back reaction and/or the equilibrium concentrations of the two redox couples (reaction 6).[28]... 

---