Ethylmercury (sometimes ethyl mercury) is a

cation An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...

composed of an organic CH₃CH₂- species (an

ethyl group In organic chemistry, an ethyl group (abbr. Et) is an alkyl substituent with the formula , derived from ethane (). ''Ethyl'' is used in the International Union of Pure and Applied Chemistry's nomenclature of organic chemistry for a saturated ...

) bound to a mercury(II) centre, making it a type of

organometallic Organometallic chemistry is the study of organometallic compounds, chemical compounds containing at least one chemical bond between a carbon atom of an organic molecule and a metal, including alkali, alkaline earth, and transition metals, and so ...

cation, and giving it a chemical formula C₂H₅Hg⁺. The main source of ethylmercury is

thimerosal Thiomersal (INN), or thimerosal (USAN, JAN), is an organomercury compound. It is a well-established antiseptic and antifungal agent. The pharmaceutical corporation Eli Lilly and Company gave thiomersal the trade name Merthiolate. It has been us ...

Synthesis and structure

Ethylmercury (C₂H₅Hg⁺) is a substituent of compounds: it occurs as a component of compounds of the formula C₂H₅HgX where X = chloride,

thiolate In organic chemistry, a thiol (; ), or thiol derivative, is any organosulfur compound of the form , where R represents an alkyl or other organic substituent. The functional group itself is referred to as either a thiol group or a sulfhydryl grou ...

, or another organic group. Most famously X = the mercaptide group of thiosalicylic acid as in

thiomersal Thiomersal (INN), or thimerosal (USAN, JAN), is an organomercury compound. It is a well-established antiseptic and antifungal agent. The pharmaceutical corporation Eli Lilly and Company gave thiomersal the trade name Merthiolate. It has been u ...

. In the body, ethylmercury is most commonly encountered as derivatives with a thiolate attached to the mercury. In these compounds, Hg(II) has a linear or sometimes trigonal coordination geometry. Given the comparable

electronegativities Electronegativity, symbolized as , is the tendency for an atom of a given chemical element to attract shared electrons (or electron density) when forming a chemical bond. An atom's electronegativity is affected by both its atomic number and the d ...

of mercury and carbon, the mercury-carbon bond is described as covalent.

Toxicity

The toxicity of ethylmercury is well studied. Like methylmercury, ethylmercury distributes to all body tissues, crossing the

blood–brain barrier The blood–brain barrier (BBB) is a highly selective semipermeable membrane, semipermeable border of endothelium, endothelial cells that prevents solutes in the circulating blood from ''non-selectively'' crossing into the extracellular fluid of ...

and the

placental barrier The placenta is a temporary embryonic and later fetal organ that begins developing from the blastocyst shortly after implantation. It plays critical roles in facilitating nutrient, gas and waste exchange between the physically separate materna ...

, and ethylmercury also moves freely throughout the body. Risk assessment for effects on the human nervous system have been made by extrapolating from dose-response relationships for methylmercury. Estimates have suggested that ethylmercury clears from blood with a

half-life Half-life (symbol ) is the time required for a quantity (of substance) to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable ato ...

of 3–7 days in adult humans; however, this area has not been well studied.

Public health concerns

Concerns based on extrapolations from methylmercury caused thimerosal 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 without thimerosal are available). 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.

References and notes

External links

EPA Organic Mercury TEACH Chemical Summary, 2007.

EPA Chemistry Dashboard, Ethyl Mercury Ion, 2017.

ATSDR Toxicological Profile for Mercury, search "Organic Mercury".
{{Mercury compounds Organomercury compounds Cations Mercury(II) compounds

Synthesis and structure

Toxicity

Public health concerns

See also

References and notes

Further reading

External links