Cacodyl

Cacodyl

Names
Preferred IUPAC name Tetramethyldiarsane
Other names Tetramethyldiarsenic(As—As) Bis(dimethylarsenic)(As—As) Tetramethyldiarsine
Identifiers
CAS Number	471-35-2 Y
3D model (JSmol)	Interactive image Interactive image
ChemSpider	71351 Y
ECHA InfoCard	100.006.766
EC Number	207-440-4
PubChem CID	79018
UNII	11N299093L Y
CompTox Dashboard (EPA)	DTXSID30197038
InChI InChI=1S/C4H12As2/c1-5(2)6(3)4/h1-4H3 Y Key: RSKPLCGMBWEANE-UHFFFAOYSA-N Y InChI=1/C4H12As2/c1-5(2)6(3)4/h1-4H3 Key: RSKPLCGMBWEANE-UHFFFAOYAG
SMILES [As]([As](C)C)(C)C C[As](C)[As](C)C
Properties
Chemical formula	C4H12As2
Molar mass	209.983 g·mol−1
Magnetic susceptibility (χ)	-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).
Y  (what is YN ?)
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.

Preparation[]

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:

${\displaystyle \mathrm {4\ CH_{3}COOK\ +\ As_{2}O_{3}\ \longrightarrow \ ((CH_{3})_{2}As)_{2}O\ +\ 2\ K_{2}CO_{3}\ +\ 2\ CO_{2}} }$

A far better synthesis was later developed which started from the dimethyl arsine chloride and dimethyl arsine:

${\displaystyle \mathrm {\ As(CH_{3})_{2}Cl\ +\ As(CH_{3})_{2}H\ \longrightarrow \ As_{2}(CH_{3})_{4}\ +\ HCl} }$

History[]

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").^[1]

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).

From it other compounds were made, such as cacodyl fluoride, , 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.

Applications[]

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 World War I the use of cacodyl as a chemical weapon was considered, but it was never used in the war. Inorganic chemists discovered the properties of cacodyl as a ligand for transition metals.

See also[]

• Cacodylic acid
• Dimethyl(trifluoromethylthio)arsine
• Lewisite
• Trimethylarsine

References[]

• 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.
• Seyferth, Dietmar (2001). "Cadet's Fuming Arsenical Liquid and the Cacodyl Compounds of Bunsen". Organometallics. 20 (8): 1488–1498. doi:10.1021/om0101947.