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Dimethylmercury

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Dimethylmercury
Skeletal formula of dimethylmercury with all explicit hydrogen added
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IUPAC name
Dimethylmercury[1]
Other names
Dimethyl mercury[citation needed]
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3600205
593-74-8 7pxN
ChEBI CHEBI:30786 7pxY
ChemSpider 11155 7pxY
EC number 209-805-3
25889
Jmol-3D images Image
MeSH dimethyl+mercury
PubChem Template:Chembox PubChem/format
RTECS number OW3010000
UN number 3383
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Template:Chem/atomTemplate:Chem/atomTemplate:Chem/atomTemplate:Chem/atom
Molar mass 230.66 g mol−1
Appearance Colorless liquid
Density 2.961 g mL−1
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1.543
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57.9–65.7 kJ mol−1
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GHS pictograms The skull-and-crossbones pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS)The health hazard pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS)The environment pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS)
GHS signal word DANGER
H300, H310, H330, H373, H410
P260, P264, P273, P280, P284, P301+310
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
NFPA 704

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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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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.[2]

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 → Hg(CH3)2 + 2 NaI

It can also be obtained by alkylation of mercuric chloride with methyllithium:

HgCl2 + 2 LiCH3 → Hg(CH3)2 + 2 LiCl

The molecule adopts a linear structure with Hg-C bond lengths of 2.083 Å.[3]

Reactions

The most striking feature of the compound is its nonreactivity toward water, whereas 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 currently has almost no applications because of the risks involved. As with many methyl-organometallics, it is a methylating agent that can donate its methyl groups to an organic molecule; however, the development of less acutely toxic nucleophiles such as dimethylzinc and trimethylaluminium, and the subsequent introduction of Grignard reagents (organometallic halides), has essentially rendered this compound obsolete in organic chemistry. It was formerly studied for reactions in which the methylmercury cation was bonded to the target molecule, forming potent bactericides; however, the bioaccumulation and ultimate toxicity of methylmercury has largely led it to be abandoned for this purpose in favor of the related ethylmercury cation, which perform a similar function without the bioaccumulation hazard.

In toxicology, it was formerly 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.[4][5][6]

Safety

Dimethylmercury is extremely toxic and dangerous to handle. Absorption of doses as low as 0.1 mL has proven fatal.[7] The risks are enhanced because of the high vapor pressure of the liquid.[7]

Dimethylmercury passes through latex, PVC, butyl, and neoprene 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.[7][8]

Dimethylmercury crosses the blood–brain barrier easily, probably owing to formation of a complex with cysteine.[9] 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.[9]

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.[7]

See also

References

  1. ^ "dimethyl mercury - Compound Summary". PubChem Compound. USA: National Center for Biotechnology Information. 16 September 2004. Identification and Related Records. Retrieved 10 March 2012. 
  2. ^ Agency for Toxic Substances and Disease Registry (March 1999). "Toxological profile for mercury". United States Department of Health and Human Services, Public Health Service. Retrieved 16 August 2014. 
  3. ^ Holleman, A. F.; Wiberg, E. (2001). Inorganic Chemistry. San Diego: Academic Press. ISBN 0-12-352651-5. 
  4. ^ O'Halloran, T. V.; Singer, C. P. (1998-03-10). "199Hg Standards". Northwestern University. Retrieved 2012-05-24. 
  5. ^ Hoffman, R. (2011-08-01). "(Hg) Mercury NMR". Jerusalem: The Hebrew University. Retrieved 2012-05-24. 
  6. ^ "Delayed Toxic Syndromes" (PDF). Terrorism by Fear and Uncertainty. ORAU. 
  7. ^ a b c d "OSHA Safety Hazard Information Bulletin on Dimethylmercury". Safety and Health Information Bulletins (SHIBs), 1997-1998. OSHA. 1991-02-15. 
  8. ^ Cotton, S. (October 2003). "Dimethylmercury and Mercury Poisoning. The Karen Wetterhahn story". Molecule of the Month. Bristol University. 
  9. ^ a b "The Karen Wetterhahn story". Retrieved 1 September 2014. 

External links