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The same reaction is catalysed by the enzyme catalase, found in the liver, whose main function in the body is the removal of toxic byproducts ofmetabolism and the reduction of oxidative stress. The decomposition occurs more rapidly in alkali, so acid is often added as a stabilizer. The liberation of oxygen and energy in the decomposition has dangerous side-effects. Spilling high concentrations of hydrogen peroxide on a flammable substance can cause an immediate fire, which is further fueled by the oxygen released by the decomposing hydrogen peroxide. High test peroxide, or HTP (also called high-strength peroxide) must be stored in a suitable, vented container to prevent the buildup of oxygen gas, which would otherwise lead to the eventual rupture of the container. In the presence of certain catalysts, such as Fe2+ or Ti3+, the decomposition may take a different path, with free radicals such as HO· (hydroxyl) and HOO· (hydroperoxyl) being formed. A combination of H2O2 and Fe2+ is known as Fenton’s reagent. A common concentration for hydrogen peroxide is 20-volume, which means that, when 1 volume of hydrogen eroxide is decomposed, it produces 20 volumes of oxygen. A 20-volumeconcentration of hydrogen peroxide is equivalent to 1. 667 mol/dm3 (Molar solution) or about 6%. Redox reactions In acidic solutions, H2O2 is one of the most powerful oxidizers known—stronger than chlorine, chlorine dioxide, and potassium permanganate. Also, through catalysis, H2O2 can be converted intohydroxyl radicals (•OH), which are highly reactive. Oxidant/Reduced product| Oxidation potential, V| Fluorine/Hydrogen fluoride| 3. 0| Ozone/Oxygen| 2. 1| Hydrogen peroxide/Water| 1. 8| Potassium permanganate/Manganese dioxide. Chlorine dioxide/HClO| 1. 5| Chlorine/Chloride| essay writing discount 1. 4| In aqueous solutions, hydrogen peroxide can oxidize or reduce a variety of inorganic ions. When it acts as a reducing agent, oxygen gas is also produced. In acidic solutions Fe2+ is oxidized to Fe3+ (hydrogen peroxide acting as an oxidizing agent), 2 Fe2+(aq) + H2O2 + 2 H+(aq) ; 2 Fe3+(aq) + 2H2O(l) and sulfite (SO2? 3) is oxidized to sulfate (SO2? 4). However, potassium permanganate is reduced to Mn2+ by acidic H2O2. Under alkaline conditions, however, some of these reactions reverse; for example, Mn2+ is oxidized to Mn4+ (as MnO2). Other examples of hydrogen peroxide’s action as a reducing agent are reaction with sodium hypochlorite or potassium permanganate, which is a convenient method for preparing oxygen in the laboratory. NaOCl + H2O2 > O2 + NaCl + H2O 2 KMnO4 + 3 H2O2 > 2 MnO2 + 2 KOH + 2 H2O + 3 O2 Hydrogen peroxide is frequently used as an oxidizing agent in organic chemistry. One application is for the oxidation of thioethers to sulfoxides. For example, methyl phenyl sulfidecan be readily oxidized in high yield to methyl phenyl sulfoxide: Ph? S? CH3 + H2O2 > Ph? S(O)? CH3 + H2O Alkaline hydrogen peroxide is used for epoxidation of electron-deficient alkenes such as acrylic acids, and also for oxidation of alkylboranes to alcohols, the second step of hydroboration-oxidation. Formation of peroxide compounds Hydrogen peroxide is a weak acid, and it can form hydroperoxide or peroxide salts or derivatives of many metals. For example, on addition to an aqueous solution of chromic acid (CrO3) or acidic solutions of dichromate salts, it will form an unstable blue peroxide CrO(O2)2. In aqueous solution it rapidly decomposes to form oxygen gas and chromium salts. It can also produce peroxoanions by reaction with anions; for example, reaction with borax leads to sodium perborate, a bleach used in laundry detergents: Na2B4O7 + 4 H2O2 + 2 NaOH > 2 Na2B2O4(OH)4 + H2O H2O2 converts carboxylic acids (RCOOH) into peroxy acids (RCOOOH), which are themselves used as oxidizing agents. Hydrogen peroxide reacts with acetone to form acetone peroxide, and it interacts with ozone to form hydrogen trioxide, also known as trioxidane. Reaction with urea produces carbamide peroxide, used for whitening teeth. An acid-base adduct with triphenylphosphine oxide is a useful “carrier” for H2O2 in some reactions. Alkalinity Hydrogen peroxide can still form adducts with very strong acids. The superacid HF/SbF5 forms unstable compounds containing the [H3O2]+ ion. Domestic uses * Diluted H2O2 (between 3% and 8%) is used to bleach human hair when mixed with ammonium hydroxide, hence the phrase “peroxide blonde”. * It is absorbed by skin upon contact and creates a local skin capillary embolism that appears as a temporary whitening of the skin. * It is used to whiten bones that are to be put on display. 3% H2O2 is effective at treating fresh (red) blood-stains in clothing and on other items. It must be applied to clothing before blood stains can be accidentally “set” with heated water. Cold water and soap are then used to remove the peroxide treated blood. Some horticulturalists and users of hydroponics advocate the use of weak hydrogen peroxide solution in watering solutions. Its spontaneous decomposition releases oxygen that enhances a plant’s root development and helps to treat root rot (cellular root death due to lack of oxygen) and a variety of other pests. Laboratory tests conducted by fish culturists in recent years have demonstrated that common household hydrogen peroxide can be used safely to provide oxygen for small fish. Hydrogen peroxide releases oxygen by decomposition when it is exposed to catalysts such as manganese dioxide. * Hydrogen peroxide is a strong oxidizer effective in controlling sulfide and organic-related odors in wastewater collection and treatment systems. It is typically applied to a wastewater system where there is a retention time of 30 minutes to 5 hours before hydrogen sulfide is released. 1. 4