Difference Between Ethylmercury and Methylmercury

Main Difference – Ethylmercury vs Methylmercury

Ethylmercury and methylmercury are two compounds formed by the combination of alkyl groups and mercury atoms. These are cations of mercury, which means these compounds have positive electrical charges. They are known as organometallic cations since they contain organic moieties and metal moieties. Ethylmercury is a cation composed of an ethyl group bonded to a mercury(II) atom. Methylmercury is a cation composed of a methyl group bonded to a mercury(II) atom. The main difference between ethylmercury and methylmercury is that ethylmercury contains an ethyl group whereas methylmercury contains a methyl group.

Key Areas Covered

1. What is Ethylmercury
     – Definition, Chemical Properties, Toxicity
2. What is Methylmercury
     – Definition, Chemical Properties, Toxicity
3. What is the Difference Between Ethylmercury and Methylmercury
     – Comparison of Key Differences

Key Terms: Cation, Ethyl Group, Ethylmercury, Mercury, Methyl Group, Methylmercury, Organometallic Compound, Thimerosal 

What is Ethylmercury

Ethylmercury is an organometallic cation containing an ethyl group bonded to a mercury(II) atom. It is called an organometallic cation because it has an alkyl group attached to a metal atom. The overall electrical charge of this cation is +1.

The chemical formula of ethylmercury is C₂H₅Hg⁺. The molar mass of ethylmercury is 229.65 g/mol. The bond between the mercury atom and carbon atom is considered as a covalent bond. This is due to the slight difference between the electronegativity values of mercury and carbon.

Figure 1: Ethylmercury

Ethylmercury is a metabolite of thimerosal. Thimerosal is a mercury-containing compound used as a preservative in some vaccines. But at present, nearly all childhood vaccines are free of thimerosal.  Other vaccines also consist of only trace amounts. In the past, ethylmercury has been used as a fungicide for growing crops, but it was later cancelled due to its toxicity.

What is Methylmercury

Methylmercury is an organometallic cation that consists of a methyl group bonded to a mercury (II) atom. The chemical formula of methylmercury is [CH₃Hg]⁺. The molar mass of this compound is 215.627 g/mol. The IUPAC name of this compound is methylmercury(1+).

Methylmercury cation has an overall electrical charge of +1. This cation readily combines with halides such as chloride and other reactive anions such as hydroxide (OH^–) and nitrate ions (NO₃^–). The bond between mercury atom and carbon atom is considered as a covalent bond due to the slight difference between the electronegativity values of mercury and carbon.

Figure 2: Methylmercury Bonded to a Halide

Methylmercury is mainly found in fresh or saltwater fish due to bioaccumulation (the accumulation of substances, such as pesticides, or other chemicals in an organism). The amount of methylmercury present in fish varies depending on the type of fish and the size of fish. For example, high amounts are found in larger fish. That is because methylmercury bioaccumulation occurs along the food chain.

Consumption of fish is a major pathway of exposure to methylmercury. This compound is also found in some sediments, but is not a pathway exposes us to its toxicity. Methylmercury is a neurotoxicant. It can affect many areas of the brain.

Difference Between Ethylmercury and Methylmercury

Definition

Ethylmercury: Ethylmercury is an organometallic cation containing an ethyl group bonded to a mercury(II) atom.

Methylmercury: Methylmercury is an organometallic cation containing a methyl group bonded to a mercury (II) atom.

Components

Ethylmercury: Ethylmercury consists of an ethyl group bonded to a mercury(II) atom.

Methylmercury: Methylmercury consists of a methyl group bonded to a mercury(II) atom.

Sources

Ethylmercury: Ethylmercury is a metabolite of thimerosal (thimerosal is a preservative used in vaccines).

Methylmercury: Methylmercury is mainly found in fresh or saltwater fish due to bioaccumulation

Toxicity

Ethylmercury: Ethylmercury is toxic and has neurological effects.

Methylmercury: Methylmercury is a neurotoxicant, and it can affect many areas of the brain.

Conclusion

Ethylmercury and methylmercury are organometallic chemical compounds composed of alkyl groups bonded to mercury(II) atoms. The main difference between ethylmercury and methylmercury is that ethylmercury contains an ethyl group whereas methylmercury contains a methyl group.

Reference:

1. “Methylmercury(1 ).” National Center for Biotechnology Information. PubChem Compound Database, U.S. National Library of Medicine, Available here.
2. “Ethylmercury.” Wikipedia, Wikimedia Foundation, 22 Dec. 2017, Available here.

Image Courtesy:

1. “Methylmercury” By uploaded by User:Rifleman 82 – Unknown (Public Domain) via Commons Wikimedia
2. “Ethylmercury-2D” By Neparis at English Wikipedia (CC BY-SA 3.0) via Commons Wikimedia