
Space-filling model of 'cacodyl'
'Cacodyl', 'dicacodyl', 'tetramethyldiarsine', 'alkarsine' or 'Cadet's liquid' (after the French chemist Louis Claude Cadet de Gassicourt) (CH
3)
2As—As(CH
3)
2 is a poisonous oily liquid with a garlicky odor. Cacodyl undergoes spontaneous combustion in dry air.
Jöns Jakob Berzelius coined the name 'kakodyl' (later changed to cacodyl) for the dimethylarsinyl radical, (CH
3)
2As, from the Greek kakodes (evil-smelling) and hyle (matter).
It was investigated by
Edward Frankland and
Robert Bunsen and is considered one of the earliest
organometallic compounds ever discovered. It was originally made from
arsenic distilled with
potassium acetate.
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.
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