The arsenic trioxide is an inorganic compound whose chemical formula is AstwoOR3. Arsenic in its metallic state is rapidly transformed into this oxide, which is a very toxic poison that can have acute and chronic manifestations..
Since arsenic and oxygen are elements of the p block, with a relatively low electronegativity difference, it is expected that AstwoOR3 is composed of a covalent nature; that is, that the As-O bonds predominate in its solid, over the electrostatic interactions between the As ions3+ metwo-.
Acute intoxication with arsenic trioxide occurs by ingestion or inhalation, the most important manifestations of this being: severe gastrointestinal disorders, cramps, circulatory collapse, and pulmonary edema..
However, despite its toxicity, it has been used industrially; for example, in the conservation of wood, in the production of pigments, semiconductors, etc. Likewise, it was formerly used in the treatment of numerous diseases.
Arsenic trioxide is an amphoteric compound, soluble in dilute acids and alkalis, insoluble in organic solvents, and relatively soluble in water. It occurs as a solid (top image), with two crystalline forms: cubic and monoclinic.
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At room temperature, AstwoOR3 crystallizes into two monoclinic polymorphs, both found in the mineral claudetite. They have trigonal pyramid units AsO3, which are joined by their oxygen atoms to compensate for the electronic deficiency of the unit on its own.
In a polymorph the AsO units3 they are linked forming rows (claudetite I), and in the other they are linked as if they were weaving a net (claudetite II):
When all those structures that define monoclinic crystals are heated, the vibrations are such that several As-O bonds are broken, and a smaller molecule ends up prevailing: As4OR6. Its structure is shown in the image below.
It could be said to consist of a dimer of AstwoOR3. Its stability is such that it supports 800 ° C in the gas phase; but, above this temperature it fragments into As moleculestwoOR3.
The same Ace4OR6 can interact with each other to crystallize into a cubic solid, the structure of which is found in the mineral arsenolite.
Note that the image is showing the structure from a higher plane. Comparing with claudetite, its structural difference with arsenolite is evident. Here, they are discrete molecules of As4OR6 that units are maintained by Van der Waals forces.
-Arsenolite
-Arsodent
-Trisenox
-Claudetita
197.84 g / mol.
-White cubic crystals (arsenolite).
-Colorless monoclinic crystals (Claudetite).
-White or transparent solid, vitreous, amorphous lumps or crystalline powder.
Toilet.
Tasteless.
460 ºC.
-313 ºC (Claudetite).
-274 ºC (Arsenolite).
485 º C (sublimates).
17 g / L at 18 ºC (20 g / L at 25 ºC).
Soluble in acids (especially hydrochloric acid) and alkalis. Practically insoluble in chloroform and ether.
-3.85 g / cm3 (cubic crystals);
-4.15 g / cm3 (rhombic crystals).
2.47 10-4 mmHg at 25 ºC.
It is not combustible, but on heating it can create toxic smoke that may include arsine..
In the presence of moisture it can be corrosive to metals.
77 kJ / mol.
1,110-4 at 25 ºC.
-1,755 (Arsenolite)
-1.92-2.01 (Claudetite).
-Arsenic trioxide is an amphoteric compound, but it functions preferentially as an acid.
-May react with hydrochloric acid or hydrofluoric acid, forming arsenic trichloride or arsenic trifluoride.
-Likewise, it reacts with strong oxidants, such as nitric acid, causing arsenic acid and nitrous oxide..
-Arsenic trioxide can react with nitric acid, producing arsine or the element arsenic, depending on the reaction conditions..
AcetwoOR3 + 6 Zn + 12 HNO3 => 2 AsH3 + 6 Zn (NO3)two + 3 HtwoOR.
This reaction served as the basis for the creation of the Marsh Test, used to detect arsenic poisoning..
AttwoOR3 It can be named according to the following nomenclatures, knowing that arsenic works with valence +3:
-Arsenous oxide (traditional nomenclature).
-Arsenic (III) oxide (stock nomenclature).
-Diarsenic trioxide (systematic nomenclature).
-It is used in the manufacture of glass, specifically as a bleaching agent. It is also used in the manufacture of ceramics, electronic products, and fireworks.
-It is added as a minor component to copper-based alloys, to increase the corrosion resistance of the alloy metals.
-The AcetwoOR3 is the starting material for the preparation of elemental arsenic, to improve electrical connections, and for the production of arsenide semiconductors
-The AcetwoOR3, as well as copper arsenate, they are used as wood preservatives. It was used in combination with copper acetate to make the Paris green pigment, used to make paints and rodenticides..
-Arsenic trioxide is a compound that has been used for centuries in the treatment of many diseases. It was used as a tonic in the treatment of nutritional disorders, neuralgia, rheumatism, arthritis, asthma, chorea, malaria, syphilis and tuberculosis.
-Likewise, it has been used in the local treatment of skin diseases, being used to destroy some superficial epitheliomas..
-Fowler's solution was used in the treatment of skin diseases and leukemia. The use of this medicine is discontinued..
-In the 1970s, Chinese researcher Zhang Tingdong conducted research on the use of arsenic trioxide in the treatment of acute promyelocytic leukemia (APL). Which led to the production of the drug Trisenox, which was approved by the US FDA.
-Trisenox has been used in APL patients who do not respond to "first-line" treatment, consisting of all-trans retinoic acid (ATRA). Arsenic trioxide has been shown to induce cancer cells to undergo apoptosis.
-Trisenox is used as a cytostatic in the treatment of refractory promyelocytic subtype (M3) from APL.
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