Cacodylic acid

Cacodylic acid is an organoarsenic compound with the formula (CH3)2AsO2H. With the formula R2As(O)OH, it is the simplest of the arsinic acids. It is a colorless solid that is soluble in water. Neutralization of cacodylic acid with base gives cacodylate salts, e.g. sodium cacodylate. They are potent herbicides. Cacodylic acid/sodium cacodylate is a buffering agent in the preparation and fixation of biological samples for electron microscopy and in protein crystallography. a In the 18th century it was found that combining and four equivalents of potassium acetate () gives a product called "Cadet's fuming liquid" which contains cacodyl oxide, and cacodyl, . Early research into "cacodyls" was reported by Robert Bunsen at the University of Marburg. Bunsen said of the compounds, "The smell of this body produces instantaneous tingling of the hands and feet, and even giddiness and insensibility... It is remarkable that when one is exposed to the smell of these compounds the tongue becomes covered with a black coating, even when no further evil effects are noticeable". His work in this field led to an increased understanding of the methyl group. Cacodyl oxide, , is often considered the first organometallic compound to be prepared synthetically. Cacodylic acid and its salts were incorporated into herbicides by a large variety of manufacturers under numerous brand names. APC Holdings Corp. sold cacodylic acid and its salts under the Phytar brand name. The variety used in Vietnam (as Agent Blue) was Phytar 560G. "Agent Blue", a mixture of cacodylic acid and sodium cacodylate was used during the Vietnam War as a defoliant. Cacodylic acid is a weak acid with a pKa of around 6.25. Cacodylic acid can be reduced to dimethylarsine , which is a versatile intermediate for the synthesis of other organoarsenic compounds: Cacodylic acid is highly toxic by ingestion, inhalation, or skin contact. The U.S. EPA states that all forms of arsenic are a serious risk to human health and the United States Agency for Toxic Substances and Disease Registry ranked arsenic as number 1 in its 2001 Priority List of Hazardous Substances at Superfund sites.

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Organoarsenic chemistry

Organoarsenic chemistry is the chemistry of compounds containing a chemical bond between arsenic and carbon. A few organoarsenic compounds, also called "organoarsenicals," are produced industrially with uses as insecticides, herbicides, and fungicides. In general these applications are declining in step with growing concerns about their impact on the environment and human health. The parent compounds are arsane and arsenic acid. Despite their toxicity, organoarsenic biomolecules are well known.

Cacodyl

Cacodyl, also known as dicacodyl or tetramethyldiarsine, (CH3)2As–As(CH3)2, is an organoarsenic compound that constitutes a major part of "Cadet's fuming liquid" (named after the French chemist Louis Claude Cadet de Gassicourt). It is a poisonous oily liquid with an extremely unpleasant garlicky odor. Cacodyl undergoes spontaneous combustion in dry air. Cacodyl is also the name of the functional group or radical (CH3)2As. A mixture of dicacodyl and cacodyl oxide ((CH3)2As–O–As(CH3)2) was first prepared by Cadet by the reaction of potassium acetate with arsenic trioxide.

Arsine

Arsine (IUPAC name: arsane) is an inorganic compound with the formula AsH3. This flammable, pyrophoric, and highly toxic pnictogen hydride gas is one of the simplest compounds of arsenic. Despite its lethality, it finds some applications in the semiconductor industry and for the synthesis of organoarsenic compounds. The term arsine is commonly used to describe a class of organoarsenic compounds of the formula AsH3−xRx, where R = aryl or alkyl. For example, As(C6H5)3, called triphenylarsine, is referred to as "an arsine".

Arsenic methylation dynamics in a rice paddy soil anaerobic enrichment culture

Rizlan Bernier-Latmani, Julien Maillard, Alexandre Bagnoud, Leia Soraya Véronique Falquet, Matthew Charles Reid

Methylated arsenic (As) species represent a significant fraction of the As accumulating in rice grains, and there are geographic patterns in the abundance of methylated arsenic in rice that are not understood. The microorganisms driving As biomethylation i ...

Amer Chemical Soc2017

Geochemical and hydrologic controls on the mobilization of arsenic derived from herbicide application

Janet Gordon Hering

The fate and transport of As was examined at an industrial site where soil- and groundwater contamination are derived from the application of As2O3 as a herbicide. Application of arsenical herbicides was discontinued in the 1970s and soils in the source ar ...

2009