Cacodyl
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| Names | |||
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| Preferred IUPAC name
Tetramethyldiarsane | |||
| Other names
Tetramethyldiarsenic(As—As)
Bis(dimethylarsenic)(As—As) | |||
| Identifiers | |||
3D model (JSmol)
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| ECHA InfoCard | 100.006.766 | ||
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PubChem CID
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CompTox Dashboard (EPA)
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| Properties | |||
| C4H12As2 | |||
| Molar mass | 209.983 g·mol−1 | ||
| -99.9·10−6 cm3/mol | |||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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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.[1]
Cacodyl is also the name of the functional group or radical (CH3)2As.
Preparation
[edit]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. A subsequent reduction yields a mixture of several methylated arsenic compounds including dicacodyl.
The global reaction (mass balance) corresponding to the oxide formation is the following:
- 4 CH3COOK + As2O3 → ((CH3)2As)2O + 2 K2CO3 + 2 CO2
A more efficient synthesis was later developed which started from the dimethyl arsine chloride and dimethyl arsine:
- As(CH3)2Cl + As(CH3)2H → As2(CH3)4 + HCl
History
[edit]Robert Wilhelm Bunsen coined the name kakodyl (later modified to cacodyl in English) for the dimethylarsinyl radical, (CH3)2As, from the Greek κακώδης kakōdēs ("evil-smelling") and ὕλη hylē ("matter").[2]
It was investigated by Edward Frankland and (for over six years) by Robert Bunsen and is considered the earliest organometallic compound ever discovered (even though arsenic is not a true metal). Bunsen began studying it in the 1830's and had determined its chemical composition by 1843, during this time Bunsen discovered cacodyl's flammability and extreme unpleasant odor.[3] As this was prior to the invention of the fume hood, to avoid the unpleasant odor of the chemical Bunsen worked quickly and breathed through a long glass tube that extended to the outside of his laboratory. Despite these precautions Bunsen learned the hard way just how dangerous and toxic cacodyl could be, he nearly died of arsenic poisoning and lost sight in one of his eyes after a glass vial of cacodyl exploded in close proximity to his face.[3]
From it other compounds were made, such as cacodyl fluoride, cacodyl chloride, et cetera. One compound, cacodyl cyanide, was particularly awful. In Bunsen's words "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".[3]
Work on cacodyl led Bunsen to the postulation of "methyl radicals" as part of the then-current radical theory.
Applications
[edit]Cacodyl was used to try to prove the radical theory of Jöns Jacob Berzelius, which resulted in a wide use of cacodyl in research laboratories. Afterward interest in the toxic, malodorous compound decreased. During the Civil War & World War I the use of cacodyl as a chemical weapon was considered, but it was never used in either war.[4] However it was used during the Vietnam War under the codename Agent Blue as an herbicide to kill crops and deprive the Vietcong of food.[5] Inorganic chemists discovered the properties of cacodyl as a ligand for transition metals.[6]
Toxicity
[edit]All of the cacodyl compounds are toxic, and overall typically cause some of the same symptoms as arsenic poisoning, with severe side effects occurring with, ingestion, skin contact and inhalation and can cause extreme skin irritation & itching.[7] Acute exposure can be fatal, initial symptoms of exposure include headache, eye irritation & redness, and strong garlic odor from the breath.[8] Additional symptoms include muscle weakness, malaise, increased thirst, muscle cramps, seizures, toxic delirium and shock. Symptoms of chronic exposure can also include nausea, vomiting, weight loss, abdominal pain, and diarrhea. Severe exposure also causes systemic symptoms like hypotension, tachycardia, pulmonary edema and ventricular fibrillation.[8] Cacodyl is also a known carcinogen, chronic exposure has been known to cause bladder cancer, kidney cancer, liver cancer and thyroid cancer.[9]
See also
[edit]- Cacodylic acid
- Dimethyl(trifluoromethylthio)arsine
- Lewisite
- Trimethylarsine
- Cacodyl cyanide
- Cacodyl oxide
References
[edit]- ^ Seyferth, Dietmar (2001). "Cadet's Fuming Arsenical Liquid and the Cacodyl Compounds of Bunsen". Organometallics. 20 (8): 1488–1498. doi:10.1021/om0101947.
- ^ Berzelius, Jöns Jacob (1841). "Kakodyl". Jahresberichte über die Fortschritte der Physischen Wissenschaften. 20: 526–539.
- ^ a b c Nichsolson, John (30 June 2007). "Historical highlights in organoarsenic chemistry". Education in Chemistry. Royal Society of Chemistry. Retrieved 11 February 2025.
- ^ Hasegawa, PharmD, Guy R. (May 2008). "Proposals for Chemical Weapons during the American Civil War". Military Medicine. 173 (5): 499–506. doi:10.7205/MILMED.173.5.499. Retrieved 11 February 2025.
- ^ Freemantle, Michael (25 January 2019). "Cacodyl Chemistry Podcast". Chemistry World. Retrieved 11 February 2025.
- ^ Seyferth, Dietmar (9 April 2001). "Cadet's Fuming Arsenical Liquid and the Cacodyl Compounds of Bunsen". Organometallics. 20 (8). American Chemical Society. Part III. Later Work on Cadet's Fuming Liquid and the Cacodyl Compounds. doi:10.1021/om0101947. Retrieved 11 February 2025.
- ^ Seyferth, Dietmar (9 April 2001). "Cadet's Fuming Arsenical Liquid and the Cacodyl Compounds of Bunsen". Organometallics. 20 (8). Cambridge, Massachusetts: Department of Chemistry Massachusetts Institute of Technology. Part II. The Investigations of R. W. Bunsen. doi:10.1021/om0101947. Retrieved 11 February 2025.
- ^ a b "SODIUM CACODYLATE MATERIAL SAFETY DATASHEET". Cameo Chemicals. Retrieved 11 February 2025.
- ^ Yamamoto, S.; Konishi, Y.; Matsuda, T.; Murai, T.; Shibata, M.A.; Matsui-Yuasa I; Otani, S.; Kuroda, K.; Endo, G.; Fukushima, S. (15 March 1995). "Cancer induction by an organic arsenic compound, dimethylarsinic acid (cacodylic acid), in F344/DuCrj rats after pretreatment with five carcinogens". Cancer Research. 55 (6). First Department of Pathology, Osaka City University Medical School. PMID 7882321. Retrieved 11 February 2025.
- John H. Burns and Jürg Waser (1957). "The Crystal Structure of Arsenomethane" (PDF). J. Am. Chem. Soc. 79 (4): 859–864. doi:10.1021/ja01561a020. hdl:1911/18207.