scavenging of •OH by excess H+, hence reducing its reaction rate. Whereas at high pH, the reaction slows down due to precipitation of Fe(OH)3, lowering the concentration of the Fe3+ species in solution. Solubility of iron species is directly governed by the solution's pH. Fe3+ is about 100 times less soluble than Fe2+ in natural water at near-neutral pH, the ferric ion concentration is the limiting factor for the reaction rate. Under high pH conditions, the stability of the H2O2 is also affected, resulting in its self-decomposition. Higher pH also decreased the redox potential of •OH thereby reducing its effectiveness. pH plays a crucial role in the formation of free radicals and hence the reaction performance. Thus ongoing research has been done to optimize pH and amongst other parameters for greater reaction rates. {| class="wikitable" |+Impacts of operation pH on reaction rate ! rowspan="2" |Low pH |Formation of [Fe(H2O)6]2+ complex, hence reducing Fe2+ for radical generation |- |Scavenging of •OH by excess H+ |- ! rowspan="3" |High pH |Lower redox potential of •OH |- |Self-decomposition of H2O2 due to decreased stability at high pH |- |Precipitation of Fe(OH)3 species in solution |} Biomedical implications The Fenton reaction has different implications in biology because it involves the formation of free radicals by chemical species naturally present in the cell under in vivo conditions. Transition-metal ions such as iron and copper can donate or accept free electrons via intracellular reactions and so contribute to the formation, or at the contrary to the scavenging, of free radicals. Superoxide ions and transition metals act in a synergistic way in the appearance of free radical damages. Therefore, although the clinical significance is still unclear, it is one of the viable reasons to avoid iron supplementation in patients with active infections, whereas other reasons include iron-mediated infections. Applications Fenton's reagent is used as a sewage treatment agent. Fenton's reagent can be used in different chemical procesess that supply hydroxyl ion or oxidize certain compounds: The first stage of Fenton’s reaction (oxidation of Fe3+ with hydrogen peroxide) is used in Haber–Weiss reaction Fenton's reagent can be used in organic synthesis reactions: e.g. hydroxylation of arenes via a free radical substitution Conversion of benzene into phenol by using Fenton's reagent Oxidation of barbituric acid into alloxan. Coupling reactions of alkanes See also Carbon monoxide-releasing molecules References Further reading External links Reference Library Peroxide Applications Companies that use Fenton's