Dimethylmercury is an extremely toxic organomercury compound with the formula (methyl)2Hg. A volatile, flammable, dense and colorless liquid, dimethylmercury is one of the strongest known . Less than 0.1 mL is capable of inducing severe mercury poisoning resulting in death.
Synthesis, structure, and reactions
The compound was one of the earliest
reported, reflecting its considerable stability. The compound was first prepared by George Buckton in 1857 by a reaction of
methylmercury iodide with potassium cyanide:
- 2 CH3HgI + 2 KCN → Hg(CH3)2 + 2 KI + (CN)2 + Hg
Later,
Edward Frankland discovered that it could be synthesized by treating
sodium amalgam with
methyl :
- Hg + 2 Na + 2 Methyl iodide → Hg(CH3)2 + 2 Sodium iodide
It can also be obtained by
alkylation of mercuric chloride with
methyllithium:
- HgCl2 + 2 LiCH3 → Hg(CH3)2 + 2 Lithium chloride
The molecule adopts a linear structure with Hg–C bond lengths of 2.083 Å.
Reactivity and physical properties
Dimethylmercury is stable in water and reacts with mineral acids at a significant rate only at elevated temperatures,
whereas the corresponding
organocadmium and
organozinc compounds (and most metal alkyls in general) hydrolyze rapidly. The difference reflects the high electronegativity of Hg (Pauling EN = 2.00) and the low affinity of Hg(II) for oxygen ligands. The compound undergoes a redistribution reaction with mercuric chloride to give methylmercury chloride:
- (CH3)2Hg + HgCl2 → 2 CH3HgCl
Whereas dimethylmercury is a
volatile liquids,
methylmercury is a crystalline solid.
Use
Dimethylmercury has few practical applications because of its danger to human life. It has been studied for reactions involving bonding
methylmercury cations to target molecules, forming potent
, but methylmercury's
bioaccumulation and ultimate toxicity has led to it being largely abandoned in favor of the less toxic
ethylmercury and
diethylmercury compounds, which perform a similar function without the bioaccumulation hazard.
In toxicology, it still finds limited use as a reference toxin. It is also used to calibrate NMR spectroscopy instruments for detection of mercury (δ 0 ppm for 199Hg NMR), although diethylmercury and less toxic mercury salts are now preferred.
Around 1960, Phil Pomerantz, a man working at the Bureau of Naval Weapons, suggested that dimethylmercury be used as a fuel mix with red fuming nitric acid.
Safety
Dimethylmercury is extremely toxic and dangerous to handle. Absorption of doses as low as 0.1 mL can result in severe mercury poisoning.
The risks are enhanced because of the compound's high
vapor pressure.
Since it is highly lipophilic, it absorbs through the skin and into body fat very easily and can permeate many materials, including many plastics and rubber compounds.
Permeation tests showed that several types of disposable latex or polyvinyl chloride gloves (typically, about 0.1 mm thick), commonly used in most Laboratory and clinical settings, had high and maximal rates of permeation by dimethylmercury within 15 seconds.
Dimethylmercury is metabolized after several days to methylmercury.
Incidents
-
As early as 1865, two workers in the laboratory of Edward Frankland died after exhibiting progressive neurological symptoms following accidental exposure to the compound.
-
Karen Wetterhahn, a professor of chemistry at Dartmouth College, died in 1997, ten months after spilling only a few drops of dimethylmercury onto her latex gloves.
-
Christoph Bulwin, a 40-year-old German database administrator for IG Bergbau, Chemie, Energie, claimed to have been attacked with a syringe-tipped umbrella on 15 July 2011 in Hanover, Germany. Bulwin, who died a year later from mercury poisoning, had said he confiscated the syringe, which was later found to contain dimethylmercury.
See also
External links
