Cacodylic acid is an

organoarsenic compound Organoarsenic chemistry is the chemistry of Chemical compound, compounds containing a chemical bond between arsenic and carbon. A few organoarsenic compounds, also called "organoarsenicals," are produced industrially with uses as insecticides, herb ...

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 ...

. 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 weed killers, 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 is a solution where the pH does not change significantly on dilution or if an acid or base is added at constant temperature. Its pH changes very little when a small amount of strong acid or base is added to it. Buffer solution ...

in the preparation and fixation of biological samples for

electron microscopy An electron microscope is a microscope that uses a beam of electrons as a source of illumination. It uses electron optics that are analogous to the glass lenses of an optical light microscope to control the electron beam, for instance focusing i ...

and in

protein crystallography X-ray crystallography is the experimental science of determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to diffract in specific directions. By measuring the angles and ...

History

In the 18th century it was found that combining

arsenic trioxide Arsenic trioxide is an inorganic compound with the formula . As an industrial chemical, its major uses include the manufacture of wood preservatives, pesticides, and glass. It is sold under the brand name Trisenox among others when used as a m ...

() and four equivalents of

potassium acetate Potassium acetate (also called potassium ethanoate), (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 ...

() gives a product called "

Cadet's fuming liquid Cadet's fuming liquid was a red-brown oily liquid prepared in 1760 by the French chemist Louis Claude Cadet de Gassicourt (1731-1799) by the reaction of potassium acetate with arsenic trioxide. It consisted mostly of dicacodyl (((CH3)2As)2) ...

" 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 () is a public research university located in Marburg, Germany. It was founded in 1527 by Philip I, Landgrave of Hesse, which makes it one of Germany's oldest universities and the oldest still operating Prote ...

. 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 (whereas normal methane has the formula ). In formulas, the group is often abbreviated a ...

. 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 ...

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

s 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 Phytar 560G, a mixture of cacodylic acid and sodium cacodylate, was used during the

Vietnam War The Vietnam War (1 November 1955 – 30 April 1975) was an armed conflict in Vietnam, Laos, and Cambodia fought between North Vietnam (Democratic Republic of Vietnam) and South Vietnam (Republic of Vietnam) and their allies. North Vietnam w ...

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 d ...

under the name "

Agent Blue Agent Blue is one of the " rainbow herbicides" that is known for 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 water. ...

Reactions

Cacodylic acid is a

weak acid Acid strength is the tendency of an acid, symbolised by the chemical formula , to dissociate into a proton, , and an anion, . The dissociation or ionization of a strong acid in solution is effectively complete, except in its most concentrated s ...

with a pK_a of around 6.25. Cacodylic acid can be reduced to dimethylarsine , which is a versatile intermediate for the synthesis of other organoarsenic compounds: : : When treated with

hydrogen sulfide Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is toxic, corrosive, and flammable. Trace amounts in ambient atmosphere have a characteristic foul odor of rotten eggs. Swedish chemist ...

, dithiocacodylic acid results: :

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, inge ...

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 U.S. Department of Health and Human Services (HHS). The agency focuses on minimizing human health risks associated with exposure to hazar ...

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 agent that promotes the development of cancer. Carcinogens can include synthetic chemicals, naturally occurring substances, physical agents such as ionizing and non-ionizing radiation, and biologic agents such as viruse ...

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