Arsenite

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In chemistry, an arsenite is a chemical compound containing an arsenic oxyanion where arsenic has oxidation state +3. Note that in fields that commonly deal with groundwater chemistry, arsenite is used generically to identify soluble AsIII anions. IUPAC have recommended that arsenite compounds are to be named as arsenate(III), for example ortho-arsenite is called trioxidoarsenate(III). Ortho-arsenite contrasts to the corresponding anions of the lighter members of group 15, phosphite which has the structure HPO2−3 and nitrite, NO−2 which is bent. [1]

Contents

A number of different arsenite anions are known:

In all of these the geometry around the AsIII centers are approximately trigonal, the lone pair on the arsenic atom is stereochemically active. [1] Well known examples of arsenites include sodium meta-arsenite which contains a polymeric linear anion, (AsO−2)n, and silver ortho-arsenite, Ag3AsO3, which contains the trigonal AsO3−3 anion.

Preparation of arsenites

Some arsenite salts can be prepared from an aqueous solution of As2O3. Examples of these are the meta-arsenite salts and at low temperature, hydrogen arsenite salts can be prepared, such as Na2H2As4O8, NaAsO2·4H2O, Na2HAsO3·5H2O and Na5(HAsO3)(AsO3)·12H2O. [5]

Arsenite minerals

A number of minerals contain arsenite anions: reinerite, Zn3(AsO3)2; [2] finnemanite, Pb5Cl(AsO3)3; [2] paulmooreite, Pb2As2O5; [2] stenhuggarite, CaFeSbAs2O7 (contains a complex polymeric anion); [2] schneiderhöhnite, FeII
FeIII
3(AsO3)(As2O5)2; [6] magnussonite, Mn5(OH)(AsO3)3; [2] trippkeite, CuAs2O4; [2] trigonite, Pb3Mn(AsO3)2(HAsO3); [2] tooeleite, Fe6(AsO3)4(SO4)(OH)4·4H2O. [7]

Arsenites in the environment

Arsenic can enter groundwater due to naturally occurring arsenic at deeper levels or from mine workings. Arsenic(III) can be removed from water by a number of methods, oxidation of AsIII to AsV for example with chlorine followed by coagulation with for example iron(III) sulfate. Other methods include ion-exchange and filtration. Filtration is only effective if arsenic is present as particulates, if the arsenite is in solution it passes through the filtration membrane. [8]

Uses

Sodium arsenite is used in the water gas shift reaction to remove carbon dioxide. Fowler's solution first introduced in the 18th century was made up from As2O3 [9] as a solution of potassium meta-arsenite, KAsO2. [10]

Arsenic in its trioxide, As2O3, (brand name Trisenox, ATO) is used as a chemotherapy drug against acute promyelocytic leukaemia (APL), a type of myeloid leukemia. [11] The detailed mechanism of action is unknown, but it is suspected to speed up apoptosis of cancer cells. Arsenic trioxide triggers morphological changes and DNA fragmentations in NB4 in vitro model for APL. It also degrades retinoic acid receptor alpha (RARA). [12] RARA gene is important regulator of premyelocytic immune cell development, differentiation, and apoptosis. [13]

Bacteria using and generating arsenite

Some species of bacteria obtain their energy by oxidizing various fuels while reducing arsenates to form arsenites. The enzymes involved are known as arsenate reductases.

In 2008, bacteria were discovered that employ a version of photosynthesis with arsenites as electron donors, producing arsenates (just like ordinary photosynthesis uses water as electron donor, producing molecular oxygen). The researchers conjectured that historically these photosynthesizing organisms produced the arsenates that allowed the arsenate-reducing bacteria to thrive. [14]

In humans, arsenite inhibits pyruvate dehydrogenase (PDH complex) in the pyruvate-acetyl CoA reaction, by binding to the –SH group of lipoamide, a participant coenzyme. It also inhibits the oxoglutarate dehydrogenase complex by the same mechanism. The inhibition of these enzymes disrupts energy production.

Related Research Articles

<span class="mw-page-title-main">Arsenic</span> Chemical element with atomic number 33 (As)

Arsenic is a chemical element with the symbol As and the atomic number 33. It is a metalloid and one of the pnictogens, and therefore shares many properties with its group 15 neighbors phosphorus and antimony. Arsenic is a notoriously toxic heavy metal. It occurs naturally in many minerals, usually in combination with sulfur and metals, but also as a pure elemental crystal. It has various allotropes, but only the grey form, which has a metallic appearance, is important to industry.

<span class="mw-page-title-main">Phosphite anion</span> Ion

A phosphite anion or phosphite in inorganic chemistry usually refers to [HPO3]2− but includes [H2PO3]− ([HPO2(OH)]−). These anions are the conjugate bases of phosphorous acid (H3PO3). The corresponding salts, e.g. sodium phosphite (Na2HPO3) are reducing in character.

<span class="mw-page-title-main">Tellurate</span> Compound containing an oxyanion of tellurium

In chemistry tellurate is a compound containing an oxyanion of tellurium where tellurium has an oxidation number of +6. In the naming of inorganic compounds it is a suffix that indicates a polyatomic anion with a central tellurium atom.

<span class="mw-page-title-main">Arsenic acid</span> Chemical compound

Arsenic acid or arsoric acid is the chemical compound with the formula H3AsO4. More descriptively written as AsO(OH)3, this colorless acid is the arsenic analogue of phosphoric acid. Arsenate and phosphate salts behave very similarly. Arsenic acid as such has not been isolated, but is only found in solution, where it is largely ionized. Its hemihydrate form (2H3AsO4·H2O) does form stable crystals. Crystalline samples dehydrate with condensation at 100 °C.

<span class="mw-page-title-main">Arsenic pentoxide</span> Chemical compound

Arsenic pentoxide is the inorganic compound with the formula As2O5. This glassy, white, deliquescent solid is relatively unstable, consistent with the rarity of the As(V) oxidation state. More common, and far more important commercially, is arsenic(III) oxide (As2O3). All inorganic arsenic compounds are highly toxic and thus find only limited commercial applications.

<span class="mw-page-title-main">Sodium arsenite</span> Chemical compound

Sodium arsenite usually refers to the inorganic compound with the formula NaAsO2. Also called sodium meta-arsenite, it is the sodium salt of arsenous acid. Sodium ortho-arsenite is Na3AsO3. The compounds are colourless solids.

Selenium trioxide is the inorganic compound with the formula SeO3. It is white, hygroscopic solid. It is also an oxidizing agent and a Lewis acid. It is of academic interest as a precursor to Se(VI) compounds.

There are three sets of Indium halides, the trihalides, the monohalides, and several intermediate halides. In the monohalides the oxidation state of indium is +1 and their proper names are indium(I) fluoride, indium(I) chloride, indium(I) bromide and indium(I) iodide.

Potassium arsenite (KAsO2) is an inorganic compound that exists in two forms, potassium meta-arsenite (KAsO2) and potassium ortho-arsenite (K3AsO3). It is composed of arsenite ions (AsO33− or AsO2−) with arsenic always existing in the +3 oxidation state. Like many other arsenic containing compounds, potassium arsenite is highly toxic and carcinogenic to humans. Potassium arsenite forms the basis of Fowler’s solution, which was historically used as a medicinal tonic, but due to its toxic nature its use was discontinued. Potassium arsenite is still, however, used as a rodenticide.

Thiophosphates (or phosphorothioates, PS) are chemical compounds and anions with the general chemical formula PS
4−xO3−
x (x = 0, 1, 2, or 3) and related derivatives where organic groups are attached to one or more O or S. Thiophosphates feature tetrahedral phosphorus(V) centers.

Thorium(IV) hydroxide is an inorganic compound with a chemical formula Th(OH)4.

Sulfidostannates, or thiostannates are chemical compounds containing anions composed of tin linked with sulfur. They can be considered as stannates with sulfur substituting for oxygen. Related compounds include the thiosilicates, and thiogermanates, and by varying the chalcogen: selenostannates, and tellurostannates. Oxothiostannates have oxygen in addition to sulfur. Thiostannates can be classed as chalcogenidometalates, thiometallates, chalcogenidotetrelates, thiotetrelates, and chalcogenidostannates. Tin is almost always in the +4 oxidation state in thiostannates, although a couple of mixed sulfides in the +2 state are known,

<span class="mw-page-title-main">Caesium ozonide</span> Chemical compound

Caesium ozonide is an oxygen-rich chemical compound of caesium, with the chemical formula CsO3. It consists of caesium cations Cs+ and ozonide anions O−3. It can be formed by reacting ozone with caesium superoxide:

<span class="mw-page-title-main">Rubidium ozonide</span> Chemical compound

Rubidium ozonide is an oxygen rich compound of rubidium. It is an ozonide, meaning it contains the ozonide anion (O3−).

Phosphide iodides or iodide phosphides are compounds containing anions composed of iodide (I−) and phosphide (P3−). They can be considered as mixed anion compounds. They are in the category of pnictidehalides. Related compounds include the phosphide chlorides, arsenide iodides antimonide iodides and phosphide bromides.

Arsenide iodides or iodide arsenides are compounds containing anions composed of iodide (I−) and arsenide (As3−). They can be considered as mixed anion compounds. They are in the category of pnictidehalides. Related compounds include the arsenide chlorides, arsenide bromides, phosphide iodides, and antimonide iodides.

An iodide nitride is a mixed anion compound containing both iodide (I−) and nitride ions (N3−). Another name is metalloiodonitrides. They are a subclass of halide nitrides or pnictide halides. Some different kinds include ionic alkali or alkaline earth salts, small clusters where metal atoms surround a nitrogen atom, layered group 4 element 2-dimensional structures, and transition metal nitrido complexes counter-balanced with iodide ions. There is also a family with rare earth elements and nitrogen and sulfur in a cluster.

Carbide chlorides are mixed anion compounds containing chloride anions and anions consisting entirely of carbon. In these compounds there is no bond between chlorine and carbon. But there is a bond between a metal and carbon. Many of these compounds are cluster compounds, in which metal atoms encase a carbon core, with chlorine atoms surrounding the cluster. The chlorine may be shared between clusters to form polymers or layers. Most carbide chloride compounds contain rare earth elements. Some are known from group 4 elements. The hexatungsten carbon cluster can be oxidised and reduced, and so have different numbers of chlorine atoms included.

The arsenite bromides are mixed anion compounds containing both arsenite and bromide ions. Similar compounds include arsenate bromides, arsenite chlorides, antimonite bromides, antimonite chlorides, and ...

<span class="mw-page-title-main">Arsenic compounds</span> Chemical compounds containing arsenic

Compounds of arsenic resemble in some respects those of phosphorus which occupies the same group (column) of the periodic table. The most common oxidation states for arsenic are: −3 in the arsenides, which are alloy-like intermetallic compounds, +3 in the arsenites, and +5 in the arsenates and most organoarsenic compounds. Arsenic also bonds readily to itself as seen in the square As3−
4 ions in the mineral skutterudite. In the +3 oxidation state, arsenic is typically pyramidal owing to the influence of the lone pair of electrons.

References

  1. 1 2 3 Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN   978-0-08-037941-8.
  2. 1 2 3 4 5 6 7 8 Carmalt, C.J & Norman, N.C. (1998). "Chapter 1: Arsenic, antimony and bismuth". In Norman, N.C. (ed.). Chemistry of Arsenic, Antimony and Bismuth. Blackie Academic and Professional. pp. 118–121. ISBN   07514-0389-X.
  3. 1 2 Hamida, M. Ben; Wickleder, M. S. (2006). "Die neuen Catena-Polyarsenite [As3O7]5− und [As4O9]6−". Zeitschrift für anorganische und allgemeine Chemie. 632 (12–13): 2109. doi:10.1002/zaac.200670065. ISSN   0044-2313.
  4. ↑ Kang, Dong-Hee; Schleid, Thomas (2006). "Sm2As4O9: Ein ungewöhnliches Samarium(III)-Oxoarsenat(III) gemäß Sm4[As2O5]2[As4O8]". Zeitschrift für anorganische und allgemeine Chemie. 632 (1): 91. doi:10.1002/zaac.200500333. ISSN   0044-2313.
  5. ↑ Sheldrick, W. S.; Häusler, H.-J. (1987). "Zur Kenntnis von Natriumarseniten im Dreistoffsystem Na2O–As2O3–H2O bei 6 °C". Zeitschrift für anorganische und allgemeine Chemie. 549 (6): 177–186. doi:10.1002/zaac.19875490618. ISSN   0044-2313.
  6. ↑ Hawthorne, Frank C. "Schneiderhoehnite, Fe2+
    Fe3+
    3    As3+
    5    O
    13    , a densely packed arsenite structure." The Canadian Mineralogist23.4 (1985): 675–679.
  7. ↑ Morin, G.; Rousse, G.; Elkaim, E. (2007). "Crystal structure of tooeleite, Fe6(AsO3)4SO4(OH)4•4H2O, a new iron arsenite oxyhydroxy-sulfate mineral relevant to acid mine drainage". American Mineralogist. 92 (1): 193–197. Bibcode:2007AmMin..92..193M. doi:10.2138/am.2007.2361. ISSN   0003-004X. S2CID   98312889.
  8. ↑ EPA, United states Environmental Protection Agency, Report 815R00012, "Technologies and Costs for the Removal of Arsenic From Drinking Water", December 2000 http://water.epa.gov/drink/info/arsenic/upload/2005_11_10_arsenic_treatments_and_costs.pdf
  9. ↑ Managing Arsenic in the Environment: From Soil to Human Health, R. Naidu, Csiro Publishing, 2006, ISBN   978-0643068681
  10. ↑ Jolliffe, D. M. (1993). "A history of the use of arsenicals in man". Journal of the Royal Society of Medicine. 86 (5): 287–289. PMC   1294007 . PMID   8505753.
  11. ↑ "Arsenic trioxide (Trisenox, ATO)". www.cancerresearchuk.org. Retrieved 2023-08-16.
  12. ↑ EMA (2018-09-17). "Trisenox". European Medicines Agency. Retrieved 2023-08-16.
  13. ↑ "RARA retinoic acid receptor alpha [Homo sapiens (human)] - Gene - NCBI". www.ncbi.nlm.nih.gov. Retrieved 2023-08-16.
  14. ↑ "Arsenic-loving bacteria rewrite photosynthesis rules", Chemistry World, 15 August 2008
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