PropertiesThe boiling point of has been extrapolated as being , approximately higher than water. In practice, hydrogen peroxide will undergo potentially explosive if heated to this temperature. It may be safely distilled at lower temperatures under reduced pressure.
StructureHydrogen peroxide () is a nonplanar molecule with (twisted) C2 ; this was first shown by in 1950 using . Although the O−O bond is a , the molecule has a relatively high of 386 cm−1 (4.62 kJ/ mol) for rotation between s via the ''trans'' configuration, and 2460 cm−1 (29.4 kJ/mol) via the ''cis'' configuration. These barriers are proposed to be due to repulsion between the s of the adjacent oxygen atoms and dipolar effects between the two O–H bonds. For comparison, the rotational barrier for is 1040 cm−1 (12.4 kJ/mol). The approximately 100° between the two O–H bonds makes the molecule . It is the smallest and simplest molecule to exhibit ism. It has been proposed that the enantiospecific interactions of one rather than the other may have led to amplification of one enantiomeric form of s and therefore an origin of in an . The molecular structures of gaseous and are significantly different. This difference is attributed to the effects of , which is absent in the gaseous state. Crystals of are with the ''D'P''4121.
Aqueous solutionsIn s, hydrogen peroxide differs from the pure substance due to the effects of hydrogen bonding between water and hydrogen peroxide molecules. Hydrogen peroxide and water form a eutectic mixture, exhibiting down as low as –56 °C; pure water has a freezing point of 0 °C and pure hydrogen peroxide of −0.43 °C. The boiling point of the same mixtures is also depressed in relation with the mean of both boiling points (125.1 °C). It occurs at 114 °C. This boiling point is 14 °C greater than that of pure water and 36.2 °C less than that of pure hydrogen peroxide.
Discoveryreported one of the first synthetic peroxides, , in 1799 as a by-product of his attempts to decompose air. Nineteen years later recognized that this compound could be used for the preparation of a previously unknown compound, which he described as ("oxygenated water") – subsequently known as hydrogen peroxide. Today, the term "oxygenated water" may appear on retail packaging referring to mixtures containing either water and hydrogen peroxide or water and dissolved oxygen. This could cause personal injury if the difference is not properly understood by the user. An improved version of Thénard's process used , followed by addition of to precipitate the byproduct. This process was used from the end of the 19th century until the middle of the 20th century. Thénard and synthesized in 1811. The bleaching effect of peroxides and their salts on s became known around that time, but early attempts of industrial production of peroxides failed. The first plant producing hydrogen peroxide was built in 1873 in . The discovery of the synthesis of hydrogen peroxide by with introduced the more efficient electrochemical method. It was first commercialized in 1908 in , , Austria. The , which is still used, was developed during the 1930s by the German chemical manufacturer in . The increased demand and improvements in the synthesis methods resulted in the rise of the annual production of hydrogen peroxide from 35,000 tonnes in 1950, to over 100,000 tonnes in 1960, to 300,000 tonnes by 1970; by 1998 it reached 2.7 million tonnes. Early attempts failed to produce neat hydrogen peroxide. Anhydrous hydrogen peroxide was first obtained by . Determination of the molecular structure of hydrogen peroxide proved to be very difficult. In 1892, the Italian physical chemist Giacomo Carrara (1864–1925) determined its molecular mass by , which confirmed that its molecular formula is H2O2. At least half a dozen hypothetical molecular structures seemed to be consistent with the available evidence. In 1934, the English mathematical physicist and the Scottish physicist Gordon Sutherland proposed a molecular structure for hydrogen peroxide that was very similar to the presently accepted one. Previously, hydrogen peroxide was prepared industrially by of , which was itself obtained by the of a solution of () in : :
ProductionToday, hydrogen peroxide is manufactured almost exclusively by the , which was originally developed by in 1939. It begins with the reduction of an (such as or the 2-amyl derivative) to the corresponding anthrahydroquinone, typically by on a . In the presence of , the anthrahydroquinone then undergoes : the labile hydrogen atoms of the s transfer to the oxygen molecule, to give hydrogen peroxide and regenerating the anthraquinone. Most commercial processes achieve oxidation by bubbling through a solution of the anthrahydroquinone, with the hydrogen peroxide then extracted from the solution and the anthraquinone recycled back for successive cycles of hydrogenation and oxidation.H. Riedl and G. Pfleiderer, U.S. Patent 2,158,525 (2 October 1936 in USA, and 10 October 1935 in Germany) to I. G. Farbenindustrie, Germany The net reaction for the anthraquinone-catalyzed process is : : + → The economics of the process depend heavily on effective recycling of the extraction solvents, the catalyst and the expensive .
Other sourcesSmall, but detectable, amounts of hydrogen peroxide can be formed by several methods. Small amounts are formed by electrolysis of dilute acid around the where hydrogen evolves if oxygen is bubbled around it. It is also produced by exposing water to from a , or an while confining it in a UV transparent vessel (e.g. quartz). It is detectable in ice water after burning a hydrogen gas stream aimed towards it and is also detectable on floating ice. Rapidly cooling humid air blown through an approximately 2,000 °C results in detectable amounts. A commercially viable process to produce hydrogen peroxide directly from the environment has been of interest for many years. Efficient direct synthesis is difficult to achieve, as the reaction of hydrogen with oxygen thermodynamically favours production of water. Systems for direct synthesis have been developed, most of which employ finely dispersed metal catalysts similar to those used for hydrogenation of organic substrates. One economic obstacle has been that direct processes give a dilute solution uneconomic for transportation. None of these has yet reached a point where they can be used for industrial-scale synthesis.
AvailabilityHydrogen peroxide is most commonly available as a solution in water. For consumers, it is usually available from pharmacies at 3 and 6 wt% concentrations. The concentrations are sometimes described in terms of the volume of oxygen gas generated; one milliliter of a 20-volume solution generates twenty milliliters of oxygen gas when completely decomposed. For laboratory use, 30 wt% solutions are most common. Commercial grades from 70% to 98% are also available, but due to the potential of solutions of more than 68% hydrogen peroxide to be converted entirely to steam and oxygen (with the temperature of the steam increasing as the concentration increases above 68%) these grades are potentially far more hazardous and require special care in dedicated storage areas. Buyers must typically allow inspection by commercial manufacturers. In 1994, world production of was around 1.9 million tonnes and grew to 2.2 million in 2006, most of which was at a concentration of 70% or less. In that year, bulk 30% sold for around 0.54 / kg, equivalent to US$1.50/kg (US$0.68/ lb) on a "100% basis". Hydrogen peroxide occurs in surface water, groundwater and in the . It forms upon illumination or natural action by substances contained in water. Sea water contains 0.5 to 14 μg/L of hydrogen peroxide, freshwater 1 to 30 μg/L and air 0.1 to 1 parts per billion.
DecompositionHydrogen peroxide decomposes to form water and oxygen with a Δ''H''
Redox reactionsThe redox properties of hydrogen peroxide depend on pH as acidic conditions exacerbate the power of s and basic conditions the power of s. As hydrogen peroxide exhibits ambivalent properties, being simultaneously an oxidizer or a reductant, its redox behavior immediately depends on pH. In acidic solutions, is a powerful , stronger than , , and . When used for cleaning laboratory glassware, a solution of hydrogen peroxide and sulfuric acid is referred to as . is a source of s (•OH), which are highly reactive. is used in the Briggs–Rauscher and Bray–Liebhafsky oscillating reactions. In ic solutions, is oxidized to (hydrogen peroxide acting as an oxidizing agent): :2 (aq) + + 2 (aq) → 2 (aq) + 2 (l) and () is oxidized to (). However, is reduced to by acidic . Under conditions, however, some of these reactions reverse; for example, is oxidized to (as ). In basic solutions, hydrogen peroxide is a strong and can reduce a variety of inorganic ions. When acts as a reducing agent, gas is also produced. For example, hydrogen peroxide will reduce and , which is a convenient method for preparing in the laboratory: :NaOCl + → + NaCl + :2 + 3 → 2 + 2 KOH + 2 + 3
Organic reactionsHydrogen peroxide is frequently used as an . Illustrative is oxidation of s to s: :Ph + → Ph + Alkaline hydrogen peroxide is used for of electron-deficient alkenes such as derivatives, and for the oxidation of alkylboranes to s, the second step of . It is also the principal reagent in the Dakin oxidation process.
Precursor to other peroxide compoundsHydrogen peroxide is a weak acid, forming or with many metals. It also converts metal oxides into the corresponding peroxides. For example, upon treatment with hydrogen peroxide, ( and ) forms a blue peroxide CrO(. This kind of reaction is used industrially to produce peroxoanions. For example, reaction with leads to , a bleach used in laundry detergents: : + 4 + 2 NaOH → 2 + converts s (RCO2H) into peroxy acids (RC(O)O2H), which are themselves used as oxidizing agents. Hydrogen peroxide reacts with to form and with to form . Hydrogen peroxide forms stable s with ( Hydrogen peroxide - urea), sodium carbonate (sodium percarbonate) and other compounds. An acid-base adduct with triphenylphosphine oxide is a useful "carrier" for in some reactions. Hydrogen peroxide is both an oxidizing agent and reducing agent. The oxidation of hydrogen peroxide by sodium hypochlorite yields singlet oxygen. The net reaction of a ferric ion with hydrogen peroxide is a ferrous ion and oxygen. This proceeds via single electron oxidation and hydroxyl radicals. This is used in some organic chemistry oxidations, e.g. in the Fenton's reagent. Only catalytic quantities of iron ion is needed since peroxide also oxidizes ferrous to ferric ion. The net reaction of hydrogen peroxide and permanganate or manganese dioxide is manganous ion; however, until the peroxide is spent some manganese ions are reoxidized to make the reaction catalytic. This forms the basis for common monopropellant rockets.
Biological functionHydrogen peroxide is formed in humans and other animals as a short-lived product in biochemical processes and is Toxicity, toxic to Cell (biology), cells. The toxicity is due to oxidation of proteins, membrane lipids and DNA by the peroxide ions. The class of biological s called superoxide dismutase (SOD) is developed in nearly all living cells as an important antioxidant agent. They promote the disproportionation of superoxide into and hydrogen peroxide, which is then rapidly decomposed by the enzyme to oxygen and water. : 2 + 2 → + : 2 H2O2 → O2 + 2 H2O Peroxisomes are organelles found in virtually all eukaryotic cells. They are involved in the catabolism of very long chain fatty acids, Branched-chain-fatty-acid kinase, branched chain fatty acids, D-amino acid, D-amino acids, polyamines, and biosynthesis of plasmalogens, ether phospholipids critical for the normal function of mammalian brains and lungs. Upon oxidation, they produce hydrogen peroxide in the following process catalyzed by flavin adenine dinucleotide (FAD): :
BleachingAbout 60% of the world's production of hydrogen peroxide is used for bleaching of wood pulp, pulp- and paper-bleaching. The second major industrial application is the manufacture of sodium percarbonate and , which are used as mild bleaches in laundry detergents. Sodium percarbonate, which is an adduct of sodium carbonate and hydrogen peroxide, is the active ingredient in such laundry products as OxiClean and Tide (detergent), Tide laundry detergent. When dissolved in water, it releases hydrogen peroxide and sodium carbonate, By themselves these bleaching agents are only effective at wash temperatures of or above and so, often are used in conjunction with bleach activators, which facilitate cleaning at lower temperatures. It has also been used as a flour bleaching agent
Production of organic compoundsIt is used in the production of various organic peroxides with dibenzoyl peroxide being a high volume example. Peroxy acids, such as peracetic acid and meta-chloroperoxybenzoic acid also are produced using hydrogen peroxide. Hydrogen peroxide has been used for creating organic peroxide-based explosives, such as . It is used as an initiator in Radical polymerization, polymerizations.
Sewage treatmentHydrogen peroxide is used in certain waste-water treatment processes to remove organic impurities. In advanced oxidation processing, the Fenton reaction gives the highly reactive (·OH). This degrades organic compounds, including those that are ordinarily robust, such as Aromatic hydrocarbon, aromatic or halogenated compounds. It can also oxidize sulfur based compounds present in the waste; which is beneficial as it generally reduces their odour.
DisinfectantHydrogen peroxide may be used for the sterilization of various surfaces, including surgical tools, and may be deployed as a vapour (Vaporized hydrogen peroxide, VHP) for room sterilization. H2O2 demonstrates broad-spectrum efficacy against viruses, bacteria, yeasts, and bacterial spores. In general, greater activity is seen against Gram-positive than Gram-negative bacteria; however, the presence of or other peroxidases in these organisms may increase tolerance in the presence of lower concentrations. Lower levels of concentration (3%) will work against most spores; higher concentrations (7 to 30%) and longer contact times will improve sporicidal activity. Hydrogen peroxide is seen as an environmentally safe alternative to -based bleaches, as it degrades to form oxygen and water and it is generally recognized as safe as an antimicrobial agent by the U.S. Food and Drug Administration (FDA).
PropellantHigh-concentration is referred to as "high-test peroxide" (HTP). It can be used either as a monopropellant (not mixed with fuel) or as the oxidizer component of a bipropellant rocket. Use as a monopropellant takes advantage of the decomposition of 70–98% concentration hydrogen peroxide into steam and oxygen. The propellant is pumped into a reaction chamber, where a catalyst, usually a silver or platinum screen, triggers decomposition, producing steam at over , which is expelled through a nozzle, generating thrust. monopropellant produces a maximal specific impulse (''I''sp) of 161 s (1.6 newton-second, kN·s/kg). Peroxide was the first major monopropellant adopted for use in rocket applications. Hydrazine eventually replaced hydrogen-peroxide monopropellant thruster applications primarily because of a 25% increase in the vacuum specific impulse. Hydrazine (toxic) and hydrogen peroxide (less-toxic [ACGIH TLV 0.01 and 1 ppm respectively]) are the only two monopropellants (other than cold gases) to have been widely adopted and utilized for propulsion and power applications. The Bell Rocket Belt, reaction control systems for Bell X-1, X-1, X-15, Centaur (rocket stage), Centaur, Project Mercury, Mercury, Little Joe (rocket), Little Joe, as well as the turbo-pump gas generators for X-1, X-15, Jupiter, Redstone and Viking used hydrogen peroxide as a monopropellant. As a bipropellant, is decomposed to burn a fuel as an oxidizer. Specific impulses as high as 350 s (3.5 kN·s/kg) can be achieved, depending on the fuel. Peroxide used as an oxidizer gives a somewhat lower ''I''sp than liquid oxygen, but is dense, storable, non-cryogenic and can be more easily used to drive gas turbines to give high pressures using an efficient ''closed cycle''. It may also be used for regenerative cooling of rocket engines. Peroxide was used very successfully as an oxidizer in World War II German rocket motors (e.g. T-Stoff, containing oxyquinoline stabilizer, for both the Walter HWK 109-500 ''Starthilfe'' RATO externally podded monopropellant booster system, and for the Walter HWK 109-509 rocket motor series used for the Me 163B), most often used with C-Stoff in a self-igniting hypergolic combination, and for the low-cost British Black Knight (rocket), Black Knight and Black Arrow launchers. In the 1940s and 1950s, the Hellmuth Walter Kommanditgesellschaft, Hellmuth Walter KG-conceived gas turbine, turbine used hydrogen peroxide for use in submarines while submerged; it was found to be too noisy and require too much maintenance compared to Submarine#Propulsion, diesel-electric power systems. Some torpedoes used hydrogen peroxide as oxidizer or propellant. Operator error in the use of hydrogen-peroxide torpedoes was named as possible causes for the sinking of HMS Sidon (P259), HMS ''Sidon'' and the Russian submarine Kursk, Russian submarine ''Kursk''. SAAB Underwater Systems is manufacturing the Torpedo 2000. This torpedo, used by the Swedish Navy, is powered by a piston engine propelled by HTP as an oxidizer and kerosene as a fuel in a bipropellant system.
Household useHydrogen peroxide has various domestic uses, primarily as a cleaning and disinfecting agent. ;Hair bleaching Diluted (between 1.9% and 12%) mixed with aqueous ammonia has been used to bleach human hair. The chemical's bleaching property lends its name to the phrase "peroxide blonde". Hydrogen peroxide is also used for tooth whitening. It may be found in most whitening toothpastes. Hydrogen peroxide has shown positive results involving teeth lightness and chroma shade parameters. It works by oxidizing colored pigments onto the Tooth enamel, enamel where the shade of the tooth may become lighter. Hydrogen peroxide may be mixed with baking soda and salt to make a homemade toothpaste. ;Removal of blood stains Hydrogen peroxide reacts with blood as a bleaching agent, and so if a blood stain is fresh, or not too old, liberal application of hydrogen peroxide, if necessary in more than single application, will bleach the stain fully out. After about two minutes of the application, the blood should be firmly blotted out. ;Acne treatmment Hydrogen peroxide may be used to treat Acne vulgaris, acne, although benzoyl peroxide is a more common treatment.
Niche uses;Glow sticks Hydrogen peroxide reacts with certain di-esters, such as phenyl oxalate ester (cyalume), to produce chemiluminescence; this application is most commonly encountered in the form of glow sticks. ;Horticulture 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. For general watering concentrations around 0.1% is in use and this can be increased up to one percent for anti-fungal actions. Tests show that plant foliage can safely tolerate concentrations up to 3%. ;Fishkeeping Hydrogen peroxide is used in aquaculture for controlling Fish mortality, mortality caused by various microbes. In 2019, the U.S. FDA approved it for control of ''Saprolegniasis'' in all coldwater finfish and all fingerling and adult coolwater and warmwater finfish, for control of external columnaris disease in warm-water finfish, and for control of ''Gyrodactylus'' spp. in freshwater-reared salmonids. Laboratory tests conducted by fish culturists have demonstrated that common household hydrogen peroxide may be used safely to provide oxygen for small fish. The hydrogen peroxide releases oxygen by decomposition when it is exposed to catalysts such as .
SafetyRegulations vary, but low concentrations, such as 5%, are widely available and legal to buy for medical use. Most over-the-counter peroxide solutions are not suitable for ingestion. Higher concentrations may be considered hazardous and typically are accompanied by a safety data sheet (SDS). In high concentrations, hydrogen peroxide is an aggressive oxidizer and will corrode many materials, including human skin. In the presence of a , high concentrations of will react violently. High-concentration hydrogen peroxide streams, typically above 40%, should be considered hazardous due to concentrated hydrogen peroxide's meeting the definition of a United States Department of Transportation, DOT oxidizer according to U.S. regulations, if released into the environment. The United States Environmental Protection Agency, EPA Reportable Quantity (RQ) for D001 hazardous wastes is , or approximately , of concentrated hydrogen peroxide. Hydrogen peroxide should be stored in a cool, dry, well-ventilated area and away from any flammable or combustible substances. It should be stored in a container composed of non-reactive materials such as stainless steel or glass (other materials including some plastics and aluminium alloys may also be suitable). Because it breaks down quickly when exposed to light, it should be stored in an opaque container, and pharmaceutical formulations typically come in brown bottles that block light. Hydrogen peroxide, either in pure or diluted form, may pose several risks, the main one being that it forms explosive mixtures upon contact with organic compounds. Distillation of hydrogen peroxide at normal pressures is highly dangerous. It is also corrosive, especially when concentrated, but even domestic-strength solutions may cause irritation to the eyes, mucous membranes, and skin.For example, see a
Adverse effects on woundsHistorically hydrogen peroxide was used for disinfecting wounds, partly because of its low cost and prompt availability compared to other s. Now it is thought to inhibit healing and to induce scarring, because it destroys newly formed skin cells. One study found that only very low concentrations (0.03% solution, this is a dilution of typical 3% Peroxide by 100 times) may induce healing, and only if not applied repeatedly. A 0.5% solution was found to impede healing. Surgical use can lead to gas embolism formation. Despite this, it is still used for wound treatment in many developing countries, and, in the United States, is prevalent as a major first aid antiseptic. Dermal exposure to dilute solutions of hydrogen peroxide causes whitening or bleaching of the skin due to microembolism caused by oxygen bubbles in the capillaries.
Use in alternative medicinePractitioners of alternative medicine have advocated the use of hydrogen peroxide for various conditions, including emphysema, influenza, AIDS, and in particular cancer. There is no evidence of effectiveness and in some cases it has proved fatal.Hydrogen Peroxide, 3%. 3. Hazards Identification
Historical incidents* On 16 July 1934, in Kummersdorf, Germany, a propellant tank containing an experimental monopropellant mixture consisting of hydrogen peroxide and ethanol exploded during a test, killing three people. * During the World War II, Second World War, doctors in Nazi concentration camps, German concentration camps experimented with the use of hydrogen peroxide injections in the killing of human subjects. * In April 1992, an explosion occurred at the hydrogen peroxide plant at Jarrie in France, due to technical failure of the computerised control system and resulting in one fatality and wide destruction of the plant. * Several people received minor injuries after a hydrogen peroxide spill on board a flight between the U.S. cities of Orlando and Memphis on 28 October 1998. * The Russian submarine Russian submarine Kursk (K-141), K-141 ''Kursk'' sailed to perform an exercise of firing dummy torpedoes at the Russian battlecruiser Pyotr Velikiy, Pyotr Velikiy, a Kirov-class battlecruiser, ''Kirov''-class battlecruiser. On 12 August 2000, at 11:28 local time (07:28 UTC), Russian submarine Kursk explosion, there was an explosion while preparing to fire the torpedoes. The only credible report to date is that this was due to the failure and explosion of one of the Kursk's hydrogen peroxide-fueled torpedoes. It is believed that High test peroxide, HTP, a form of highly concentrated hydrogen peroxide used as propellant for the torpedo, seeped through its container, damaged either by rust or in the loading procedure back on land where an incident involving one of the torpedoes accidentally touching ground went unreported. The vessel was lost with all hands. A similar incident was responsible for the loss of HMS Sidon (P259), HMS ''Sidon'' in 1955. * On 15 August 2010, a spill of about of cleaning fluid occurred on the 54th floor of 1515 Broadway, in Times Square, New York City. The spill, which a spokesperson for the New York City fire department said was of hydrogen peroxide, shut down Broadway between West 42nd and West 48th streets as fire engines responded to the HAZMAT, hazmat situation. There were no reported injuries.
See also* FOX reagent, used to measure levels of hydrogen peroxide in biological systems. * Hydrogen chalcogenide * Retr0bright, a process utilizing hydrogen peroxide to restore yellowed items such as plastic Home computer, computer cases and Video game console, game consoles.
ReferencesNotes Bibliography * * A great description of properties & chemistry of . * *