Английская Википедия:Dimethylmercury
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Dimethylmercury is an extremely toxic organomercury compound with the formula (CH3)2Hg. A volatile, flammable, dense and colorless liquid, dimethylmercury is one of the strongest known neurotoxins. Less than 0.1 mL is capable of inducing severe mercury poisoning resulting in death.[1]
Synthesis, structure, and reactions
The compound was one of the earliest organometallics 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]
- 2 CH3HgI + 2 KCN → Hg(CH3)2 + 2 KI + (CN)2 + Hg
Later, Frankland discovered that it could be synthesized by treating sodium amalgam with methyl halides:
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]
Reactivity and physical properties
Dimethylmercury is stable in water and reacts with mineral acids at a significant rate only at elevated temperatures,[4][5] 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 liquid, methylmercury chloride is a crystalline solid.[6]
Use
Dimethylmercury has few applications because of the risks involved. It has been studied for reactions involving bonding methylmercury cations to target molecules, forming potent bactericides, 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 instruments for detection of mercury (δ 0 ppm for 199Hg NMR), although diethylmercury and less toxic mercury salts are now preferred.[7][8][9]
Safety
Dimethylmercury is extremely toxic and dangerous to handle. Absorption of doses as low as 0.1 mL can result in severe mercury poisoning.[1] The risks are enhanced because of the compound's high vapor pressure.[1] 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 laboratories and clinical settings, had high and maximal rates of permeation by dimethylmercury within 15 seconds.[10] The American Occupational Safety and Health Administration advises handling dimethylmercury with highly resistant laminated gloves with an additional pair of abrasion-resistant gloves worn over the laminate pair, and also recommends using a face shield and working in a fume hood.[1][11]
Dimethylmercury is metabolized after several days to methylmercury.[10] Methylmercury crosses the blood–brain barrier easily, probably owing to formation of a complex with cysteine.[11] It easily absorbs into the body, and has a tendency to bioaccumulate. The symptoms of poisoning may be delayed by months, resulting in cases in which a diagnosis is ultimately discovered, but only at a point in which it is too late or almost too late for an effective treatment regimen to be successful.[11] Methylmercury poisoning is also known as Minamata disease.
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.[2]
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.[1][12] This incident resulted in improved safety procedures for chemical-protection clothing and fume hood use.[13]
Christoph Bulwin, a 40-year-old German database administrator for IG Bergbau, Chemie, Energie, was reportedly attacked with a syringe-tipped umbrella on 15 July 2011 in Hanover, Germany. Bulwin, who died a year later, claimed to have confiscated the syringe, which was later found to contain dimethylmercury;[14] leading to his death from mercury poisoning.[15][16][17] Police investigations, however, revealed a syringe containing a typical mercury thallium compound in Bulwin's car and mercury and thallium in thermometers at his workplace. Inconclusive antemortem and postmortem blood, urine, and tissue analysis cast doubts on the assault account. The absence of an identified assailant or motive, as well as the presence of different mercury compounds in Bulwin's car, led police to conclude that the intoxication was likely self-administered, thereby terminating the preliminary investigation.[18]
See also
References
External links
- ATSDR – ToxFAQs: Mercury
- ATSDR – Public Health Statement: Mercury
- ATSDR – MMG: Mercury
- ATSDR – Toxicological Profile: Mercury
- National Pollutant Inventory – Mercury and compounds Fact Sheet
- Chemistryworld – Death of Dr. Wetterhahn and resultant improvements in security practices
Шаблон:Chemical agents Шаблон:Mercury compounds Шаблон:Neurotoxins Шаблон:Use dmy dates
- ↑ 1,0 1,1 1,2 1,3 1,4 Шаблон:Cite web
- ↑ 2,0 2,1 Шаблон:Cite book
- ↑ Шаблон:Cite book
- ↑ Шаблон:Cite book
- ↑ Шаблон:Cite book
- ↑ Шаблон:Cite web
- ↑ Шаблон:Cite web
- ↑ Шаблон:Cite web
- ↑ Шаблон:Cite web
- ↑ 10,0 10,1 Шаблон:Cite journal
- ↑ 11,0 11,1 11,2 Шаблон:Cite journal
- ↑ Шаблон:Cite web
- ↑ Шаблон:Cite magazine
- ↑ Шаблон:Cite web
- ↑ Шаблон:Cite journal
- ↑ Шаблон:Cite news
- ↑ Шаблон:Cite magazine
- ↑ Шаблон:Cite journal
