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{{Chembox
{{Chembox
| ImageFile =
| ImageFile = MeAsO3H2.png
| ImageSize =
| ImageSize = 144
| ImageAlt =
| ImageAlt =
| PIN = Methylarsonic acid<ref>{{cite book |author=[[International Union of Pure and Applied Chemistry]] |date=2014 |title=Nomenclature of Organic Chemistry: IUPAC Recommendations and Preferred Names 2013 |publisher=[[Royal Society of Chemistry|The Royal Society of Chemistry]] |pages=916, 918 |doi=10.1039/9781849733069 |isbn=978-0-85404-182-4}}</ref>
| IUPACName =
| OtherNames =
| OtherNames = Methanearsonic acid<br/>Monomethylarsonic acid
|Section1={{Chembox Identifiers
|Section1={{Chembox Identifiers
| CASNo = 124-58-3
| CASNo = 124-58-3
| PubChem =
| PubChem = 8948
| InChI=1S/CH5AsO3/c1-2(3,4)5/h1H3,(H2,3,4,5)
⚫
| SMILES = }}
| InChIKey=QYPPRTNMGCREIM-UHFFFAOYSA-N
| EC_number=204-705-6
| RTECS=PA1575000
| UNNumber=1557
| UNII=J37VJ5709S
| Beilstein=4-04-00-03682
| ChemSpiderID=8604
⚫
| SMILES = C[As](=O)(O)O}}
|Section2={{Chembox Properties
|Section2={{Chembox Properties
| C=1|H=5|As=1|O=3
| C=1|H=5|As=1|O=3
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'''Methanearsonic acid''' is an [[organoarsenic compound]] with the formula CH<sub>3</sub>AsO<sub>3</sub>H<sub>2</sub>. It is a colorless, water-soluble solid. Salts of this compound, e.g. [[disodium methyl arsonate]], have been widely used in as a herbicides and fungicides in growing cotton and rice.<ref name=Ullmann>{{Ullmann | author = Grund, S. C.; Hanusch, K.; Wolf, H. U. | title = Arsenic and Arsenic Compounds | doi = 10.1002/14356007.a03_113.pub2 }}</ref>
'''Methylarsonic acid''' is an [[organoarsenic compound]] with the formula CH<sub>3</sub>AsO<sub>3</sub>H<sub>2</sub>. It is a colorless, water-soluble solid. Salts of this compound, e.g. [[disodium methyl arsonate]], have been widely used in as herbicides and fungicides in growing cotton and rice.<ref name=Ullmann>{{Ullmann | author = Grund, S. C. | author2 = Hanusch, K. | author3 = Wolf, H. U. | title = Arsenic and Arsenic Compounds | doi = 10.1002/14356007.a03_113.pub2 }}</ref>

==Reactions==
Near physiological pH, methanearsonic acid converts to its conjugate bases, the '''methylarsonates'''. These include CH<sub>3</sub>AsO<sub>3</sub>H<sup>−</sup> and {{chem|CH|3|AsO|3|2−}}.

==Synthesis and biosynthesis==
{{Confuse|Meyer synthesis}}
Reaction of [[arsenous acid]] with [[methyl iodide]] gives methylarsonic acid. This historically significant conversion is called the '''Meyer reaction''':<ref>{{cite journal|title=Ueber einige anomale Reaktionen|author=G. Meyer|journal=Berichte der deutschen chemischen Gesellschaft|pages=1439–1443|volume=13|year=1883|doi=10.1002/cber.188301601316}}</ref>
:As(OH)<sub>3</sub> + CH<sub>3</sub>I + NaOH → CH<sub>3</sub>AsO(OH)<sub>2</sub> + NaI + H<sub>2</sub>O
The then-novel aspect of the reaction was that alkylation occurs at arsenic, leading to oxidation of arsenic from [[oxidation state]] +3 to +5.


Near physiological pH, methanearsonic acid converts to its conjugate bases called '''methanearsonates'''. These include CH<sub>3</sub>AsO<sub>3</sub>H<sup>-</sup> and CH<sub>3</sub>AsO<sub>3</sub><sup>2-</sup>. The [[biomethylation]] of arsenic compounds is thought to start with the formation of methanearsonates. Thus, trivalent arsenic compounds are methylated to give methanearsonate. [[S-adenosylmethionine]] is the methyl donor. The methanearsonates are the precursors to dimethylarsonates, again by the cycle of reduction (to methylarsonous acid) followed by a second methylation.<ref name=Cullen/>
The [[biomethylation]] of arsenic compounds is thought to start with the formation of methanearsonates. Thus, trivalent arsenic compounds are methylated to give methanearsonate. [[S-Adenosylmethionine|''S''-Adenosylmethionine]] is the methyl donor. The methanearsonates are the precursors to [[cacodylate]]s, again by the cycle of reduction (to methylarsonous acid) followed by a second methylation.<ref name=Cullen/>


==Safety==
==Safety==
Like all arsenic compounds it is highly toxic.<ref name=Cullen>{{cite journal|title=Comparative toxicity of trivalent and pentavalent inorganic and methylated arsenicals in rat and human cells|authors=Styblo, M.; Del Razo, L. M.; Vega, L.; Germolec, D. R.; LeCluyse, E. L.; Hamilton, G. A.; Reed, W.; Wang, C.; Cullen, W. R.; Thomas, D. J.|title=Archives of Toxicology|year=2000|volume=74|pages=289-299|doi=10.1007/s002040000134}}</ref>.
Like most arsenic compounds, it is highly toxic.<ref name=Cullen>{{cite journal|title=Comparative toxicity of trivalent and pentavalent inorganic and methylated arsenicals in rat and human cells|author1=Styblo, M. |author2=Del Razo, L. M. |author3=Vega, L. |author4=Germolec, D. R. |author5=LeCluyse, E. L. |author6=Hamilton, G. A. |author7=Reed, W. |author8=Wang, C. |author9=Cullen, W. R. |author10=Thomas, D. J. |journal=Archives of Toxicology|year=2000|volume=74|pages=289–299|doi=10.1007/s002040000134}}</ref>


==References==
==References==
{{Reflist}}
<references />


[[Category:Arsonic acids| ]]
[[Category:Arsonic acids]]

Revision as of 13:33, 20 September 2023

Methylarsonic acid
Names
Preferred IUPAC name
Methylarsonic acid[1]
Other names
Methanearsonic acid
Monomethylarsonic acid
Identifiers
3D model (JSmol)
4-04-00-03682
ChemSpider
ECHA InfoCard 100.004.278 Edit this at Wikidata
EC Number
  • 204-705-6
RTECS number
  • PA1575000
UNII
UN number 1557
  • InChI=1S/CH5AsO3/c1-2(3,4)5/h1H3,(H2,3,4,5)
    Key: QYPPRTNMGCREIM-UHFFFAOYSA-N
  • C[As](=O)(O)O
Properties
CH5AsO3
Molar mass 139.970 g·mol−1
Appearance white solid
Melting point 160.5 °C (320.9 °F; 433.6 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Methylarsonic acid is an organoarsenic compound with the formula CH3AsO3H2. It is a colorless, water-soluble solid. Salts of this compound, e.g. disodium methyl arsonate, have been widely used in as herbicides and fungicides in growing cotton and rice.[2]

Reactions

Near physiological pH, methanearsonic acid converts to its conjugate bases, the methylarsonates. These include CH3AsO3H− and CH
3AsO2−
3.

Synthesis and biosynthesis

Not to be confused with Meyer synthesis.

Reaction of arsenous acid with methyl iodide gives methylarsonic acid. This historically significant conversion is called the Meyer reaction:[3]

As(OH)3 + CH3I + NaOH → CH3AsO(OH)2 + NaI + H2O

The then-novel aspect of the reaction was that alkylation occurs at arsenic, leading to oxidation of arsenic from oxidation state +3 to +5.

The biomethylation of arsenic compounds is thought to start with the formation of methanearsonates. Thus, trivalent arsenic compounds are methylated to give methanearsonate. S-Adenosylmethionine is the methyl donor. The methanearsonates are the precursors to cacodylates, again by the cycle of reduction (to methylarsonous acid) followed by a second methylation.[4]

Safety

Like most arsenic compounds, it is highly toxic.[4]

References

  1. ^ International Union of Pure and Applied Chemistry (2014). Nomenclature of Organic Chemistry: IUPAC Recommendations and Preferred Names 2013. The Royal Society of Chemistry. pp. 916, 918. doi:10.1039/9781849733069. ISBN 978-0-85404-182-4.
  2. ^ Grund, S. C.; Hanusch, K.; Wolf, H. U. "Arsenic and Arsenic Compounds". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a03_113.pub2. ISBN 978-3527306732.
  3. ^ G. Meyer (1883). "Ueber einige anomale Reaktionen". Berichte der deutschen chemischen Gesellschaft. 13: 1439–1443. doi:10.1002/cber.188301601316.
  4. ^ a b Styblo, M.; Del Razo, L. M.; Vega, L.; Germolec, D. R.; LeCluyse, E. L.; Hamilton, G. A.; Reed, W.; Wang, C.; Cullen, W. R.; Thomas, D. J. (2000). "Comparative toxicity of trivalent and pentavalent inorganic and methylated arsenicals in rat and human cells". Archives of Toxicology. 74: 289–299. doi:10.1007/s002040000134.
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