Ethylmercury
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3D model (JSmol)
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| 3903035 | |||
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| EC Number |
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| 323460 | |||
PubChem CID
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CompTox Dashboard (EPA)
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| Properties | |||
| C2H5Hg+ | |||
| Molar mass | 229.65 g/mol | ||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Ethylmercury (sometimes ethyl mercury) is a cation composed of an organic CH3CH2— species (an ethyl group) bound to a mercury(II) centre, making it a type of organometallic cation, and giving it a chemical formula C2H5Hg+. The main source of ethylmercury is thimerosal.[1]
Synthesis and structure
[edit]
Ethylmercury (C2H5Hg+) is a substituent of compounds: it occurs as a component of compounds of the formula C2H5HgX where X = chloride, thiolate, or another organic group. Most famously X = the mercaptide group of thiosalicylic acid as in thiomersal. In the body, ethylmercury is most commonly encountered as derivatives with a thiolate attached to the mercury.[2] In these compounds, Hg(II) has a linear or sometimes trigonal coordination geometry. Given the comparable electronegativities of mercury and carbon, the mercury-carbon bond is described as covalent.[3]: p. 79
Toxicity
[edit]The toxicity of ethylmercury is well studied.[4][1] Like methylmercury, ethylmercury distributes to all body tissues, crossing the blood–brain barrier and the placental barrier, and ethylmercury also moves freely throughout the body.[5] Risk assessment for effects on the human nervous system have been made by extrapolating from dose-response relationships for methylmercury.[1] Estimates have suggested that ethylmercury clears from blood with a half-life of 3—7 days in adult humans.[6][7] In monkeys, it clears from brain tissue with a half-life of 24 days and blood in 7 days.[8]
It is a fungicide but has been banned from use in the U.S. on food grain and even on seeds only used to grow crops.[9]
Public health concerns
[edit]Concerns based on extrapolations of the effect of methylmercury caused thimerosal to be removed from U.S. childhood vaccines in 1999, but it remains in use in all multi-dose vaccines and flu shots (though many single use vaccines without thimerosal are available).[10] Researchers have argued that risk assessments based on methylmercury were overly conservative in light of observations that ethylmercury is eliminated from the body and the brain significantly faster than methylmercury.[1] Moreover, the same researchers have argued that inorganic mercury metabolized from ethylmercury, despite its much longer half-life in the brain, is much less toxic than the inorganic mercury produced from mercury vapor, for reasons not yet understood.[1]
See also
[edit]References and notes
[edit]- ^ a b c d e Clarkson, Thomas W.; Magos, Laszlo (September 2006). "The toxicology of mercury and its chemical compounds". Critical Reviews in Toxicology. 36 (8): 609–62. doi:10.1080/10408440600845619. PMID 16973445. S2CID 37652857.
- ^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
- ^ Elschenbroich C (2016). "Main-Group Organometallics [§6.2.3 Organomercury Compounds]". Organometallics (3rd ed.). New York, NY: John Wiley & Sons. pp. 78–86. ISBN 978-3-527-80514-3. Retrieved 13 February 2017.
- ^ Counter, S.Allen; Buchanan, Leo H. (2004). "Mercury exposure in children: A review". Toxicology and Applied Pharmacology. 198 (2): 209–230. doi:10.1016/j.taap.2003.11.032. PMID 15236954.
- ^ Clarkson TW, Vyas JB, Ballatori N (October 2007). "Mechanisms of mercury disposition in the body". American Journal of Industrial Medicine. 50 (10): 757–64. doi:10.1002/ajim.20476. PMID 17477364.
- ^ Clifton JC (April 2007). "Mercury exposure and public health". Pediatric Clinics of North America. 54 (2): 237–69, viii. doi:10.1016/j.pcl.2007.02.005. PMID 17448359.[verification needed]
- ^ "Weekly Epidemiological Record, vol. 87, 30 (pp 277–288)". WHO. 2012-07-27. Archived from the original on October 19, 2014. Retrieved 2020-05-10.
- ^ Burbacher, Thomas M. (2005). "Comparison of Blood and Brain Mercury Levels in Infant Monkeys Exposed to Methylmercury or Vaccines Containing Thimerosal". Environmental Health Perspectives. 113 (8): 1015–1021. doi:10.1289/ehp.7712. ISSN 0091-6765. PMC 1280342. PMID 16079072.
See researchgate.net/figure/A-semilogarithmic-plot-of-washout-of-total-Hg-in-blood-and-the-brain-after-four-weekly-im_fig6_7681091
- ^ "Organic Mercury--TEACH Chemical Summary--U.S. EPA, Toxicity and Exposure Assessment for Children's Health" (PDF).
Methyl- and ethylmercury have been used previously as fungicides on seeds used for growing crops, but such use is currently cancelled in the U.S.
- ^ Research, Center for Biologics Evaluation and (2019-04-05). "Thimerosal and Vaccines". FDA.
Further reading
[edit]- Mitchell WJ (2005). "Carbohydrate assimilation by saccharolytic clostridia". Environmental Health Perspectives. 143 (3): 245–50. doi:10.1289/ehp.113-a543. PMC 1280369.
- DHHS ATSDR, US (March 2013). "Addendum to the Toxicological Profile for Mercury (Alkyl and Dialkyl Compounds)" (PDF). CDC.gov. Retrieved 13 February 2017.
- EPA, OA, US (9 September 2015). "Thimerosal in Vaccines". EPA.gov. Retrieved 13 February 2017.
- Santos JC, da Silva IM, Braga TC, de Fátima Â, Figueiredo IM, Santos JC (February 2018). "Thimerosal changes protein conformation and increase the rate of fibrillation in physiological conditions: Spectroscopic studies using bovine serum albumin (BSA)". International Journal of Biological Macromolecules. 113: 1032–1040. doi:10.1016/j.ijbiomac.2018.02.116. PMID 29476861.