Cacodylic acid
Encyclopedia
Cacodylic acid is the chemical compound
with the formula
(CH3)2AsO2H. Derivatives of cacodylic acid, cacodylates, were frequently used as herbicide
s. For example, "Agent Blue
," one of the chemicals used during the Vietnam War
, is a mixture of cacodylic acid and sodium cacodylate. Sodium cacodylate is frequently used as a buffering agent
in the preparation and fixation of biological samples for electron microscopy.
s was done 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 radical
.
Cacodyloxide, ((CH3)2As)2O, is often considered the first organometallic compound to be prepared synthetically.
(CH3CO2K) gives a product called "Cadet's fuming liquid
" which contains cacodyl oxide
, ((CH3)2As)2O and cacodyl
, ((CH3)2As).
Cacodylic acid can be reduced to dimethylarsine (III) derivatives, which are versatile intermediates for the synthesis of other organoarsenic compounds:2AsO2H + 2 Zn + 4 HCl → (CH3)2AsH + 2 ZnCl2 + 2 H2O2AsO2H + SO2 + HI → (CH3)2AsI + SO3 + H2O
and also decreased DNA production and shorter DNA strands. While not itself a strong carcinogen, cacodylic acid does promote tumors in the presence of carcinogens in organs such as the kidneys and liver.
Chemical compound
A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...
with the formula
Chemical formula
A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....
(CH3)2AsO2H. Derivatives of cacodylic acid, cacodylates, were frequently used as herbicide
Herbicide
Herbicides, also commonly known as weedkillers, are pesticides used to kill unwanted plants. Selective herbicides kill specific targets while leaving the desired crop relatively unharmed. Some of these act by interfering with the growth of the weed and are often synthetic "imitations" of plant...
s. For example, "Agent Blue
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 was sprayed on rice paddies and other crops in an attempt to deprive the Viet Cong of valuable crops. Agent Blue is a mixture of two arsenic-containing compounds, sodium...
," one of the chemicals used during the Vietnam War
Vietnam War
The Vietnam War was a Cold War-era military conflict that occurred in Vietnam, Laos, and Cambodia from 1 November 1955 to the fall of Saigon on 30 April 1975. This war followed the First Indochina War and was fought between North Vietnam, supported by its communist allies, and the government of...
, is a mixture of cacodylic acid and sodium cacodylate. Sodium cacodylate is frequently used as a buffering agent
Buffering agent
A buffering agent is a weak acid or base used to maintain the acidity of a solution at a chosen value. The function of a buffering agent is to prevent a rapid change in pH when acids or bases are added to the solution. Buffering agents have variable properties—some are more soluble than others;...
in the preparation and fixation of biological samples for electron microscopy.
History
Significant early research into cacodylCacodyl
Cacodyl, dicacodyl, tetramethyldiarsine, alkarsine or minor part of the "Cadet's fuming liquid" 2As—As2 is a poisonous oily liquid with a garlicky odor...
s was done by Robert Bunsen
Robert Bunsen
Robert Wilhelm Eberhard Bunsen was a German chemist. He investigated emission spectra of heated elements, and discovered caesium and rubidium with Gustav Kirchhoff. Bunsen developed several gas-analytical methods, was a pioneer in photochemistry, and did early work in the field of organoarsenic...
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 radical
Methyl radical
Methyl radical is a trivalent radical derived from methane, produced by the ultraviolet disassociation of halomethanes....
.
Cacodyloxide, ((CH3)2As)2O, is often considered the first organometallic compound to be prepared synthetically.
Synthesis and reactions
In the 18th century it was known that combining As2O3 and four equivalents of potassium acetatePotassium acetate
Potassium acetate is the potassium salt of acetic acid.-Preparation:It can be prepared by reacting a potassium-containing base such as potassium hydroxide or potassium carbonate with acetic acid:...
(CH3CO2K) gives a product called "Cadet's fuming liquid
Cadet's fuming liquid
Cadet's fuming liquid was the first organometallic compound to be synthesized. In 1760, the French chemist Louis Claude Cadet de Gassicourt synthesized a red liquid by the reaction of potassium acetate with arsenic trioxide....
" which contains cacodyl oxide
Cacodyl oxide
Cacodyl oxide is a chemical compound of the formula [2As]2O. This organoarsenic compound is primarily of historical significance as it is sometimes considered to be the first organometallic compound synthesized in relatively pure form....
, ((CH3)2As)2O and cacodyl
Cacodyl
Cacodyl, dicacodyl, tetramethyldiarsine, alkarsine or minor part of the "Cadet's fuming liquid" 2As—As2 is a poisonous oily liquid with a garlicky odor...
, ((CH3)2As).
Cacodylic acid can be reduced to dimethylarsine (III) derivatives, which are versatile intermediates for the synthesis of other organoarsenic compounds:2AsO2H + 2 Zn + 4 HCl → (CH3)2AsH + 2 ZnCl2 + 2 H2O2AsO2H + SO2 + HI → (CH3)2AsI + SO3 + H2O
Health effects
Cacodylic acid is highly toxic by ingestion, inhalation, or skin contact. Once thought to be a byproduct of inorganic arsenic detoxification, it is now believed to have serious health consequences of its own. It has been shown to be teratogenic in rodents, most often causing cleft palate but also fetal fatality at high doses. It has been shown to be genotoxic in human cells, causing apoptosisApoptosis
Apoptosis is the process of programmed cell death that may occur in multicellular organisms. Biochemical events lead to characteristic cell changes and death. These changes include blebbing, cell shrinkage, nuclear fragmentation, chromatin condensation, and chromosomal DNA fragmentation...
and also decreased DNA production and shorter DNA strands. While not itself a strong carcinogen, cacodylic acid does promote tumors in the presence of carcinogens in organs such as the kidneys and liver.