The different forms of the anion are the next ones:
- ortho-arsenite: AsO33−
- meta-arsenite: AsO2−
Arsenite contrasts to the corresponding anions of the lighter members of group 15, phosphite which has the structure HPO32− and nitrite, NO2− which is bent. Sodium arsenite is used in the water gas shift reaction to remove carbon dioxide. Arsenites are salts of arsenious acid.
Note that in fields that commonly deal with groundwater chemistry, arsenite commonly refers to As2O3, the acid anhydride of arsenious acid. Its white odorless crystals are toxic and very soluble in water. It occurs in nature as arsenolite and claudetite, and is also a byproduct of metal smelting. Its main use is in producing chromated copper arsenate (CCA) to treat timber. It is also used for arsenic pesticides, glass production, pharmaceuticals and non-ferrous alloys.
Bacteria using and generating arsenate
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.
In humans, arsenite inhibits pyruvate dehydrogenase (PDH complex) in the pyruvate acetyl CoA reaction, and binds to the SH group of lipoamide, a participant coenzyme. In this inhibition, arsenite poisoning affects energy production in the body.
- Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 0080379419.
- Arsenic-loving bacteria rewrite photosynthesis rules, Chemistry World, 15 August 2008
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