Ethylmercury

Ethylmercury
Identifiers
CAS Number	21687-36-5 ;
3D model (JSmol)	Interactive image;
Beilstein Reference	3903035
ChEBI	CHEBI:33204 ;
ChemSpider	5247 ;
Gmelin Reference	323460
PubChem CID	7862 chloride; 66943 bromide;
CompTox Dashboard (EPA)	DTXSID00274466 ;
	InChI InChI=1S/C2H5.Hg/c1-2;/h1H2,2H3;/q;+1 Key: MJOUBOKSWBMNGQ-UHFFFAOYSA-N ;
	SMILES CC[Hg+];
Properties
Chemical formula	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).

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 thiomersal.^[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, however this area has not been well studied.^[6]^[7]

Public health concerns

Concerns based on extrapolations from methylmercury caused thiomersal to be removed from U.S. childhood vaccines, starting in 1999, but remains in all multi dose vaccines and flu shots (though many single use vaccines with no thimerosal are available^[8]). Clarkson has 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. Moreover, Clarkson has 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]

References and notes

^ ^a ^b ^c ^d Clarkson TW, Magos L (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.
^ "Weekly Epidemiological Record, vol. 87, 30 (pp 277–288)". WHO. 2012-07-27. Retrieved 2020-05-10.
^ Research, Center for Biologics Evaluation and (2019-04-05). "Thimerosal and Vaccines". FDA.

External links

[Clarkson-1] Clarkson TW, Magos L (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.

[Elschenbroich16-3] 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.

[Mercury_exposure_in_children:_A_rev-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.

[pmid17477364-5] 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.

[pmid17448359-6] 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.

[7] "Weekly Epidemiological Record, vol. 87, 30 (pp 277–288)". WHO. 2012-07-27. Retrieved 2020-05-10.

[8] Research, Center for Biologics Evaluation and (2019-04-05). "Thimerosal and Vaccines". FDA.

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