ICS Award
Radical Rea­ctions in Aqueous Solutions/Suspensions: A Personal Perspective

Radicals are key intermediates in a variety of important processes occurring in aqueous solutions, e.g.: biological processes, advanced oxidation processes, catalytic processes, photochemical processes of importance in solar energy conversion, environmental processes, electrochemical processes etc. Radicals are formed in a variety of chemical reactions; in electrochemical and photochemical processes; by absorption of ionizing radiation; in sono-chemical processes; in mechano-chemistry and microwave induced chemical processes. However the most convenient tools to study the properties of a given radical are radiation-chemical techniques. The nature of radicals in aqueous solutions is not fully understood, thus for example it was recently reported that OH^. radicals in aqueous media are bonded to a water molecule by a three electron two center bond, 3e-2c, often also called hemibond. Nearly all radicals are both oxidizing and ­­reducing agents. The redox potentials of radicals span the whole range possible in aqueous solutions. Nearly all the redox reactions proceed via the bridged mechanism and not via the outer-sphere mechanism. The reactions of alkyl radicals with low-valent metal complexes often yield transient complexes with metal-carbon σ bonds. Analogous transients are formed when alkyl radicals react with M°-nanoparticles and metal surfaces. The mechanisms of decomposition of these transients are discussed.

Recent unpublished results concerning the mechanisms of the Fenton Reaction, the properties of hydrogen atoms adsorbed on metal surfaces and the mechanisms of catalytic de-halogenation processes are discussed.