Cacodylic acid is an
organoarsenic compound with the
formula (CH
3)
2 AsO
2H. With the formula R
2As(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
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 ...
.
History
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
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 worl ...
. 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 to be prepared synthetically.
Cacodylic acid and its salts were incorporated into
herbicides 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 it ...
(as
Agent Blue) was Phytar 560G.
"
Agent Blue," 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.
Reactions
Cacodylic acid is a
weak acid 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,
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
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 subst ...
.
See also
*
Arsenic
Arsenic is a chemical element with the symbol As and atomic number 33. Arsenic occurs in many minerals, usually in combination with sulfur and metals, but also as a pure elemental crystal. Arsenic is a metalloid. It has various allotropes, bu ...
*
Arsine
Arsine ( IUPAC name: arsane) is an inorganic compound with the formula As H3. 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 ...
*
Cacodyl oxide
References
Further reading
*
* Elschenbroich, C; Salzer, A. (1992) Organometallics, 2nd Edition
External links
Case Studies in Environmental Medicine - Arsenic Toxicity
{{DEFAULTSORT:Cacodylic Acid
Arsenical herbicides
Organoarsenic compounds
IARC Group 2B carcinogens