The hydrogen peroxide is an inorganic compound whose chemical formula is HtwoORtwo. Of all, it is the simplest peroxide of this family of chemical compounds. Its structural formula is H-O-O-H, being this internal oxygenated bridge characteristic for all peroxides.
In 1818, the HtwoORtwo It was identified by Louies Jacques Thénard, who prepared a chemical compound which he called hydrogen peroxide at the time. It is an unstable compound, it decomposes on exposure to light, heat and some metals.
It is a very useful compound that is used in the disinfection of minor wounds, hair whitening, water treatment, etc. Although it can have harmful actions for humans, it is found in all eukaryotic cells of living beings, where it performs several beneficial functions.
Hydrogen peroxide produces the oxidation of toxic substances such as phenols, ethanol, formaldehyde, etc., products that are eliminated by the liver and kidneys. In addition, it contributes to the destruction of bacteria phagocytosed by neutrophilic leukocytes and macrophages..
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The upper image shows the structure of the H moleculetwoORtwo (H-O-O-H), with the red spheres corresponding to the oxygen atoms, and the white ones the hydrogen atoms. Note that the molecule is not flat, and that the H atoms are not eclipsed in space (facing each other).
Interestingly, to the HtwoORtwo It is difficult for it to rotate its central simple O-O bond, so the positions of these H's cannot be interchanged; one won't go down while the other goes up.
Why? Because in the two oxygen atoms there are two free pairs of electrons, which gives a total of eight very close electrons that repel each other due to their negative charges..
Even so, the O-O bond is susceptible to slight rotation due to interactions with its environment..
For example, by bringing the two thumbs together, with the index fingers extended and the others closed, as if drawing a court, and then turning the thumbs in such a way that one of the index fingers points forward and the other back, you will have a approximate representation of HtwoORtwo.
If a body touches either index finger, the thumbs will rotate in response to this interaction; however, they will immediately return to their original position due to the electronic repulsions mentioned above. These rotations thus frame the dynamic aspects of this molecule.
In the liquid state the HtwoORtwo manages to establish hydrogen bonds (HOOH-OtwoHtwo), since otherwise its high boiling point (150 ºC) compared to water would not be explained.
Once it passes into the gas phase, the H moleculestwoORtwo presumably it can no longer form such bridges, due not only to the greater intermolecular distance, but also the hydrogen atoms would be the first to touch in case of collisions (this can be visualized by resorting to the finger model again).
Meanwhile, in the solid phase, the angle of the planes established by the H is 90º (put the index fingers perpendicular). Now hydrogen bonds become even more important and H moleculestwoORtwo are arranged in a crystal of tetragonal structure.
sBottle with hydrogen peroxide. In pharmacies it is achieved with a concentration of 3% m / v. Source: Pixnio.
-Hydrogen peroxide
-Antioxidan
-Oxidanol
-Perhydroxic acid
-O-hydroxyol
-Peroxide
34.0147 g / mol
Pale blue (concentrated) or colorless liquid. It is slightly more viscous and dense than water. It is distilled for safety at low temperatures and under reduced pressure, since it decomposes on heating in an explosive form.
Sharp or an ozone-like odor.
Bitter
Solid 1.71 g / cm3
The densities of its aqueous solutions depend on their concentration; for example, at 27% it has a density of 1.10 g / cm3, while at 50%, 1.13 g / cm3
- 0.43 ºC
150.2 ° C. This value has been obtained by extrapolation, since hydrogen peroxide decomposes at high temperatures.
Miscible ≥ 100 mg / mL at 25 ºC
It is soluble in ether and alcohols, but insoluble in petroleum ether. Decomposes into water and oxygen in many organic solvents.
Log P = - 0.43
5 mmHg at 30 ºC.
pKa = 11.72
Hydrogen peroxide solutions are slightly acidic. For example, a 35% one has a pH of 4.6; but by concentrating at 90%, the pH becomes less acidic: 5.1.
1,4061
1,245 cPoise at 20 ºC.
1,267 J / gK (gas)
2,619 J / gK (liquid)
1,519 J / gK
Stable under recommended conditions. It is further stabilized by the addition of acetanilide and tin salts.
Corrosive
It decomposes on exposure to light or in the presence of oxidizing and reducing substances. It also decomposes on heating. When it decomposes it releases water and oxygen, and is favored by an increase in pH and temperature, as well as by the presence of the enzyme catalase..
80.4 dynes / cm at 20 ° C
The HtwoORtwo It acts as an oxidizing agent in acidic solutions of ferrous iron (Fetwo+) to ferric iron (F3+); also oxidizes the sulfite ion (SO3two-) to sulfate ion (SO4two-).
It can also act as a reducing agent in the presence of basic solutions, reducing sodium hypochlorite (NaOCl) and potassium permanganate (KMnO4) with the release of oxygen.
Hydrogen peroxide is used in the paper industry in pulp and paper bleaching, which consumes most of its annual production.
Hydrogen peroxide is a mild antiseptic to prevent infection of small wounds, scrapes, and burns. It is also used as a mouthwash and to relieve mild irritation of the mouth due to the presence of canker sores or gingivitis..
It is also used to disinfect surfaces, the interior of refrigerators, water and combat excessive bacterial growth in water systems and cooling towers. Hydrogen peroxide releases free oxygen radicals, which break down pollutants.
Hydrogen peroxide is used in the manufacture of laundry bleaching detergents, including sodium percarbonate. This compound is a complex of sodium carbonate and hydrogen peroxide that, when dissolved in water, separates into its components.
Diluted hydrogen peroxide is used in hair bleaching, prior to staining. It is also used to whiten teeth, as well as part of a homemade toothpaste.
Hydrogen peroxide is used as the monopropellant or oxidizing component of a bipropolent rocket. It decomposes releasing oxygen and water, a characteristic that allowed its use as a propellant.
It is pumped into a reaction cell with the presence of a catalyst that accelerates said decomposition. During this, a high temperature water vapor is produced.
When the steam is expelled through a gap, it produces an impulse. The V-80 submarine, built in 1940, used oxygen generated from hydrogen peroxide in its turbines; called Walter's turbine system.
Initially, hydrogen peroxide was obtained industrially by hydrolysis of ammonium persulfate, [(NH4)twoStwoOR8] or the electrolysis of ammonium bisulfate, NH4HSO4.
Hydrogen peroxide is currently obtained industrially through the use of anthraquinone. The process is carried out in four stages: hydrogenation, filtration, oxidation, extraction and purification..
Alkylantroquinone is hydrogenated by passing hydrogen gas through a hydrogenator loaded with alumina and a small amount of the catalyst (palladium). The temperature is kept at 45 ºC with permanent stirring.
Alkyldroquinone is converted to alkylanthrahydroquinone and tetrahydroalkylanthrahydroquinone, the latter being selected for its greater convenience for the following procedures.
The solution containing the hydrogenated anthraquinone is filtered to remove traces of the catalyst that it may contain..
The filtered solution is oxidized by passing air through it, forming low-purity hydrogen peroxide..
The solution with the hydrogen peroxide passes through a liquid-liquid extraction column. The water flows through the column, while the solution with the hydrogen peroxide is pumped through it.
The water reaches the bottom of the extractor with a hydrogen peroxide concentration between 25 and 35% w / w. Then, it is purified by vacuum distillation, to a hydrogen peroxide concentration of 30%. Finally stabilizes and is stored.
Hydrogen peroxide is a corrosive agent, so on contact with the skin it causes severe irritation, as well as a temporary whitening (image above). It can also cause eye damage, itching, rash, redness, and blistering..
Inhalation causes irritation to the nose, throat and lungs. Meanwhile, repeated exposure can cause bronchitis, cough, phlegm, and shortness of breath. And as if it were not enough, it also generates headaches, dizziness, nausea and vomiting.
Severe exposure to hydrogen peroxide can cause fluid to build up in the lungs, known as pulmonary edema - a serious condition that requires prompt medical attention..
The Occupational Safety and Health Administration (OSHA) has established the maximum allowable for hydrogen peroxide of 1 ppm in a work environment in an 8-hour shift. However, as it is a mutagenic compound, exposure should be kept to a minimum..
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