|Jmol-3D images||Image 1|
|Molar mass||230.66 g mol−1|
|Density||2.961 g mL−1|
|Melting point||−43 °C (−45 °F; 230 K)|
|Boiling point||93 to 94 °C (199 to 201 °F; 366 to 367 K)|
|Refractive index (nD)||1.543|
|Std enthalpy of
|57.9–65.7 kJ mol−1|
|GHS signal word||DANGER|
|GHS hazard statements||H300, H310, H330, H373, H410|
|GHS precautionary statements||P260, P264, P273, P280, P284, P301+310|
|EU classification||T+ N|
|R-phrases||R26/27/28, R33, R50/53|
|S-phrases||(S1/2), S13, S28, S36, S45|
|Flash point||5 °C (41 °F; 278 K)|
|Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)|
|(what is: / ?)|
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.
Synthesis, structure, reactions
- HgCl2 + 2 LiCH3 → Hg(CH3)2 + 2 LiCl
The molecule adopts a linear structure with Hg-C bond lengths of 2.083 Å.
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
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.
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.
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.
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- 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.
- Holleman, A. F.; Wiberg, E. (2001). Inorganic Chemistry. San Diego: Academic Press. ISBN 0-12-352651-5.
- O'Halloran, T. V.; Singer, C. P. (1998-03-10). "199Hg Standards". Northwestern University. Retrieved 2012-05-24.
- Hoffman, R. (2011-08-01). "(Hg) Mercury NMR". Jerusalem: The Hebrew University. Retrieved 2012-05-24.
- "Delayed Toxic Syndromes" (pdf). Terrorism by Fear and Uncertainty. ORAU.
- "OSHA Safety Hazard Information Bulletin on Dimethylmercury". Safety and Health Information Bulletins (SHIBs), 1997-1998. OSHA. 1991-02-15.
- Cotton, S. (October 2003). "Dimethylmercury and Mercury Poisoning. The Karen Wetterhahn story". Molecule of the Month. Bristol University.
- "The Karen Wetterhahn story". Retrieved 1 September 2014.
- ATSDR - ToxFAQs: Mercury
- ATSDR - Public Health Statement: Mercury
- ATSDR - ALERT! Patterns of Metallic Mercury Exposure, 6/26/97
- ATSDR - MMG: Mercury
- ATSDR - Toxicological Profile: Mercury
- National Pollutant Inventory - Mercury and compounds Fact Sheet