5953. Methanearsonic Acid

Nomenclature

CAS number: 124-58-3
Methylarsonic acid; methylarsinic acid; monomethylarsinic acid.
CH5AsO3; mol wt 139.97.
C 8.58%, H 3.60%, As 53.53%, O 34.29%.

Description and references

Prepd from sodium arsenite and methyl iodide: A. J. Quick, R. Adams, J. Am. Chem. Soc. 44, 805 (1922). The disodium salt is easily prepd by treating sodium arsenite with dimethyl sulfate at 85°: R. H. Uhlinger, R. V. Cook, Ind. Eng. Chem. 11, 105 (1919) DOI. Other routes are by the reaction of methyl chloride with sodium arsonate under pressure: Miller et al., US 2442372 (1948); by the reaction of dimethyl sulfate with a solution of arsenic trioxide in sodium hydroxide: Schwerdle, US 2889347 (1959). Acute toxicity: T. B. Gaines, R. E. Linder, Fundam. Appl. Toxicol. 7, 299 (1986) DOI PubMed. Review of toxicology and human exposure: Toxicological Profile for Arsenic (PB2000-108021, 2000) 468 pp.

Chemical structure

Properties

Monoclinic, spear-shaped plates from abs alcohol. Pleasant acid taste. mp 161°. Strong dibasic acid. Freely sol in water; sol in alcohol.

Derivative

Monosodium salt.

Nomenclature

CAS number: 2163-80-6
Monosodium methylarsonate; MSMA; Ansar 6.6 (ISK Biosci); Bueno (ISK Biosci); Daconate (ISK Biosci); Weed Hoe (Vineland).
CH4AsNaO3; mol wt 161.95.
C 7.42%, H 2.49%, As 46.26%, Na 14.20%, O 29.64%.

Properties

LD50 in adult male, female rats (mg/kg): 1105, 1059 orally (Gaines, Linder).

Derivative

Disodium salt.

Nomenclature

CAS number: 144-21-8
Disodium methylarsonate; DSMA; Ansar 8100 (ISK Biosci); Arrhenal (Cleary); Arsinyl (Cleary); Clout (Scott); Crab-E-Rad (Vineland); Dal-E-Rad (Vineland); Sodar.
CH3AsNa2O3; mol wt 183.93.
C 6.53%, H 1.64%, As 40.73%, Na 25.00%, O 26.10%.

Properties

Hydrated crystals contg 5H2O or 6H2O. One gram dissolves in about one ml water; slightly sol in alcohol. LD50 in adult male, female rats (mg/kg): 928, 821 orally (Gaines, Linder).

Use

Herbicide.