Cacodylic acid is an

organoarsenic compound 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 fun ...

with the

formula In science, a formula is a concise way of expressing information symbolically, as in a mathematical formula or a ''chemical formula''. The informal use of the term ''formula'' in science refers to the general construct of a relationship betwe ...

(CH₃)₂ AsO₂H. With the formula R₂As(O)OH, it is the simplest of the

arsinic acids Arsinic acids are organoarsenic compounds with the formula R2AsO2H. They are formally, but not actually, related to arsinic acid, a hypothetical compound of the formula H2AsO2H. Arsinic acids are monoprotic, weak acids. They react with sodium s ...

. 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

herbicide Herbicides (, ), also commonly known as weedkillers, are substances used to control undesired plants, also known as weeds.EPA. February 201Pesticides Industry. Sales and Usage 2006 and 2007: Market Estimates. Summary in press releasMain page f ...

s. Cacodylic acid/sodium cacodylate is a

buffering agent A buffer solution (more precisely, pH buffer or hydrogen ion buffer) is an aqueous solution consisting of a mixture of a weak acid and its conjugate base, or vice versa. Its pH changes very little when a small amount of strong acid or base is ...

in the preparation and fixation of biological samples for

electron microscopy An electron microscope is a microscope that uses a beam of accelerated electrons as a source of illumination. As the wavelength of an electron can be up to 100,000 times shorter than that of visible light photons, electron microscopes have a hi ...

History

In the 18th century it was found that combining and four equivalents of

potassium acetate Potassium acetate (CH3COOK) is the potassium salt of acetic acid. It is a hygroscopic solid at room temperature. Preparation It can be prepared by treating a potassium-containing base such as potassium hydroxide or potassium carbonate with acetic ...

() gives a product called " Cadet's fuming liquid" which contains

cacodyl oxide Cacodyl oxide is a chemical compound of the formula CH3)2Assub>2O. This organoarsenic compound is primarily of historical significance since it is sometimes considered to be the first organometallic compound synthesized in relatively pure form. ...

, and

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 poisono ...

, . Early research into "

s" was reported by

Robert Bunsen Robert Wilhelm Eberhard Bunsen (; 30 March 1811 – 16 August 1899) was a German chemist. He investigated emission spectra of heated elements, and discovered caesium (in 1860) and rubidium (in 1861) with the physicist Gustav Kirchhoff. The Bu ...

at the

University of Marburg The Philipps University of Marburg (german: Philipps-Universität Marburg) was founded in 1527 by Philip I, Landgrave of Hesse, which makes it one of Germany's oldest universities and the oldest still operating Protestant university in the wor ...

. 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 In organic chemistry, a methyl group is an alkyl derived from methane, containing one carbon atom bonded to three hydrogen atoms, having chemical formula . In formulas, the group is often abbreviated as Me. This hydrocarbon group occurs in ma ...

. Cacodyl oxide, , is often considered the first

organometallic compound Organometallic chemistry is the study of organometallic compounds, chemical compounds containing at least one chemical bond between a carbon atom of an organic molecule and a metal, including alkali, alkaline earth, and transition metals, and s ...

to be prepared synthetically. Cacodylic acid and its salts were incorporated into

s by 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 Vietnam or Viet Nam ( vi, Việt Nam, ), officially the Socialist Republic of Vietnam,., group="n" is a country in Southeast Asia, at the eastern edge of mainland Southeast Asia, with an area of and population of 96 million, making ...

(as

Agent Blue Agent Blue is one of the " rainbow herbicides" that is known for its use by the United States during the Vietnam War. It contained a mixture of dimethylarsinic acid (also known as cacodylic acid) and its related salt, sodium cacodylate, and w ...

) was Phytar 560G. "

," a mixture of cacodylic acid and sodium cacodylate was used during the

Vietnam War The Vietnam War (also known by #Names, other names) was a conflict in Vietnam, Laos, and Cambodia from 1 November 1955 to the fall of Saigon on 30 April 1975. It was the second of the Indochina Wars and was officially fought between North Vie ...

as a

defoliant A defoliant is any herbicidal chemical sprayed or dusted on plants to cause their leaves to fall off. Defoliants are widely used for the selective removal of weeds in managing croplands and lawns. Worldwide use of defoliants, along with the ...

Reactions

Cacodylic acid is a

weak acid Acid strength is the tendency of an acid, symbolised by the chemical formula HA, to dissociate into a proton, H+, and an anion, A-. The dissociation of a strong acid in solution is effectively complete, except in its most concentrated solutions ...

with a pK_a of 6. Cacodylic acid can be reduced to dimethylarsine , which is a versatile intermediate for the synthesis of other organoarsenic compounds:Burrows, G. J. and Turner, E. E., "A New Type of Compound containing Arsenic", Journal of the Chemical Society Transactions, 1920, 1374-1383 : :

Health effects

Cacodylic acid is highly toxic by

ingestion Ingestion is the consumption of a substance by an organism. In animals, it normally is accomplished by taking in a substance through the mouth into the gastrointestinal tract, such as through eating or drinking. In single-celled organisms in ...

inhalation Inhalation (or Inspiration) happens when air or other gases enter the lungs. Inhalation of air Inhalation of air, as part of the cycle of breathing, is a vital process for all human life. The process is autonomic (though there are exceptions ...

, 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 The Agency for Toxic Substances and Disease Registry (ATSDR) is a federal public health agency within the United States Department of Health and Human Services. The agency focuses on minimizing human health risks associated with exposure to haz ...

ranked arsenic as number 1 in its 2001 Priority List of Hazardous Substances at Superfund sites. Arsenic is classified as a Group-A

carcinogen A carcinogen is any substance, radionuclide, or radiation that promotes carcinogenesis (the formation of cancer). This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes. Several radioactive sub ...

References

External links

Case Studies in Environmental Medicine - Arsenic Toxicity

{{DEFAULTSORT:Cacodylic Acid Arsenical herbicides Organoarsenic compounds IARC Group 2B carcinogens

History

Reactions

Health effects

See also

References

Further reading

External links