Ethylmercury

Ethylmercury
Identifiers
3D model (JSmol)
3903035
ChEBI
ChemSpider
EC Number
  • chloride: 203-478-0
  • bromide: 203-477-5
  • iodide: 219-471-0
323460
UNII
  • InChI=1S/C2H5.Hg/c1-2;/h1H2,2H3;/q;+1 checkY
    Key: MJOUBOKSWBMNGQ-UHFFFAOYSA-N checkY
  • chloride: InChI=1S/C2H5.ClH.Hg/c1-2;;/h1H2,2H3;1H;/q;;+1/p-1
    Key: QWUGXIXRFGEYBD-UHFFFAOYSA-M
  • bromide: InChI=1S/C2H5.BrH.Hg/c1-2;;/h1H2,2H3;1H;/q;;+1/p-1
    Key: UREACWLAXSOUKG-UHFFFAOYSA-M
  • iodide: InChI=1S/C2H5.Hg.HI/c1-2;;/h1H2,2H3;;1H/q;+1;/p-1
    Key: BYIGJUQTUPMNMF-UHFFFAOYSA-M
  • CC[Hg+]
  • chloride: CC[Hg]Cl
  • bromide: CC[Hg]Br
  • iodide: CC[Hg]I
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).
☒N verify (what is checkY☒N ?)

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

Structures of two main types of complexes derived from "ethylmercury". X− = anion, L = neutral Lewis base.

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

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

Main article: Thiomersal and vaccines

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

References and notes

  1. ^ 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.
  2. ^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
  3. ^ 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.
  4. ^ 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.
  5. ^ 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.
  6. ^ 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]
  7. ^ "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.
  8. ^ 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
  9. ^ "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.
  10. ^ Research, Center for Biologics Evaluation and (2019-04-05). "Thimerosal and Vaccines". FDA.

Further reading