Dimethylmercury


Dimethylmercury
Dimethylmercury
Identifiers
CAS number 593-74-8 YesY
PubChem 11645
ChemSpider 11155 YesY
UNII C60TQU15XY YesY
EC number 209-805-3
UN number 3383
MeSH Dimethyl+mercury
ChEBI CHEBI:307​86 YesY
RTECS number OW3010000
Beilstein Reference 3600205
Gmelin Reference 25889
Jmol-3D images Image 1
Image 2
Properties
Molecular formula C2H6Hg
Molar mass 230.66 g mol−1
Exact mass 232.017575796 g mol-1
Appearance Colorless liquid
Density 2.961 g cm-3
Melting point

-43 °C, 230 K, -45 °F

Boiling point

93-94 °C, 366-367 K, 199-201 °F

Hazards
EU Index 080-007-00-3
EU classification Very Toxic T+Dangerous for the Environment (Nature) N
R-phrases R26/27/28, R33, R50/53
S-phrases (S1/2), S13, S28, S36, S45, S60, S61
NFPA 704
NFPA 704.svg
4
4
1
Flash point 5 °C
 YesY (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Dimethylmercury ((CH3)2Hg) is an organomercury compound. This colorless liquid is one of the strongest known neurotoxins. It is described as having a slightly sweet smell, although inhaling enough vapor to detect its odor would be hazardous.

Contents

Synthesis, structure, reactions

The compound was one of the earliest organometallic complexes reported, reflecting its considerable stability. It is formed by treating sodium amalgam with methyl halides:

Hg + 2 Na + 2 CH3I → (CH3)2Hg + 2 NaI

It can also be obtained by alkylation of mercuric chloride with methyllithium. The molecule adopts a linear structure with Hg-C bond lengths of 2.083 Å.[1]

Reactions

The most striking feature of the compound is its nonreactivity toward water. The corresponding organocadmium and organozinc compounds hydrolyze rapidly. The difference reflects the low affinity of Hg(II) for oxygen ligands. The compound reacts with mercuric chloride to give the mixed chloro-methyl compound:

(CH3)2Hg + HgCl2 → 2 CH3HgCl

Whereas dimethylmercury is a volatile liquid, CH3HgCl is a crystalline solid.

Use

Dimethylmercury has almost no applications because of the risks involved. In toxicology, it is used as a reference toxin. It has also been used to calibrate NMR instruments for detection of mercury, although less toxic mercury salts are preferred.[2][3]

Safety

Dimethylmercury is extremely dangerous. Absorption of doses as low as 0.1 mL has proven fatal.[4] The risks are enhanced because of the high vapor pressure of the liquid.

Dimethylmercury passes through latex, PVC, butyl, and neoprene rapidly (within seconds) and is absorbed through the skin. Therefore, most laboratory gloves do not provide adequate protection from it, and the only safe precaution is to handle dimethylmercury while wearing highly resistant laminated gloves underneath long-cuffed neoprene or other heavy-duty gloves. A long face shield and work under a fume hood are also indicated.[4][5]

Dimethylmercury crosses the blood–brain barrier easily, probably owing to formation of a complex with cysteine. It is eliminated from the organism slowly, and therefore has a tendency to bioaccumulate. The symptoms of poisoning may be delayed by months, possibly too late for effective treatment.

The toxicity of dimethylmercury was highlighted with the death of the inorganic chemist Karen Wetterhahn of Dartmouth College in 1997, months after spilling no more than a few drops of this compound on her latex-gloved hand.[4]

See also

References

  1. ^ Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
  2. ^ Chris Singer (1998-03-10). "199Hg Standards". http://www.chem.northwestern.edu/~ohallo/HgNMRStandards/. Retrieved 2009-05-03. 
  3. ^ Roy Hoffman (2007-02-21). "Mercury NMR". http://chem.ch.huji.ac.il/nmr/techniques/1d/row6/hg.html. Retrieved 2009-05-03. 
  4. ^ a b c Hazard Information Bulletin - Dimethylmercury. OSHA Safety and Health Information Bulletins (SHIBs), 1997-1998
  5. ^ Simon Cotton, Dimethylmercury and mercury poisoning. The Karen Wetterhahn story. Molecule of the Month.

External links


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