Cacodyl
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IUPAC name
Tetramethyldiarsane
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| Other names
Tetramethyldiarsenic(As—As)
Tetramethyldiarsine |
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| Identifiers | |||
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3D model (Jmol)
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| ChemSpider | |||
| ECHA InfoCard | 100.006.766 | ||
| EC Number | 207-440-4 | ||
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PubChem CID
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| Properties | |||
| C4H12As2 | |||
| Molar mass | 209.98 g·mol−1 | ||
| -99.9·10−6 cm3/mol | |||
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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 (what is   ?) |
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| Infobox references | |||
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.
Cacodyl is also the name of the functional group or radical (CH3)2As.
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 reaction forming the oxide is something like:
A far better synthesis was later developed which started from the dimethyl arsine chloride and dimethyl arsine:
Jöns Jakob Berzelius coined the name kakodyl (later modified to cacodyl in English) for the dimethylarsinyl radical, (CH3)2As, from the Greek kakodes (evil-smelling) and hyle (matter).
It was investigated by Edward Frankland and (over six years) by Robert Bunsen and is considered the earliest organometallic compound ever discovered (even though arsenic is not a true metal).
From it other compounds were made, such as cacodyl fluoride, 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".
Work on cacodyl led Bunsen to the postulation of "methyl radicals" as part of the then-current radical theory.
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Wikipedia