I was reading about methyl iodide and I saw a warning to not let it come into contact with sodium amalgam or it will create dimethylmercury. I'm wondering if that's really all that it takes to create such a dangerous substance. Does simply dropping sodium mercury amalgam into a container and then pouring in some methyl iodide create dimethylmercury? I'm not really sure if these chemicals would ever need to be around each other, so I don't think an accident is super likely, but it's still kind of crazy to me.

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    $\begingroup$ Yes it really is that easy $\endgroup$
    – Waylander
    Mar 14 at 19:19
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    $\begingroup$ $\ce{Hg + 2 Na + 2 CH3I -> 2 NaI + (CH3)2Hg}$ seems quite straightforward to me. Similar reaction was used to make $\ce{(CH3CH2)4Pb}$ for gasoline, before the lead-free one. $\endgroup$
    – Poutnik
    Mar 14 at 19:36
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    $\begingroup$ Dimethylmercury is very toxic. Read about Karen Wetterhahn $\endgroup$
    – user55119
    Mar 14 at 22:14
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    $\begingroup$ You seem to have a wrong perspective on dangerous substances. Yes they are very easy to come by, they are all around us, they are more common than the opposite. The Nature is not friendly to us. $\endgroup$ Mar 15 at 20:44

2 Answers 2


Yes, it is. However, it is not crazy since these precursors are not something easily obtainable directly from nature.

This illustrates the fact that sodium itself is not that simple to find, the final step in the creation of dimethylmercury is very easy, but fortunately there are some obstacles before that, which prevent accidents.


Yes, dimethylmercury is that easy. Roughly speaking, sodium amalgam is mercury endowed with excess electrons from the electropositive sodium, and methyl iodide (an electrophile) can react with the excess electrons and the mercury atoms to form dimethylmercury. The iodide ions displaced by this reduction end up precipitated from the mercury as sodium iodide.

Dimethylmercury is especially dangerous as mercury sources go because it is much more easily absorbed through the skin or inhaled than elemental mercury or inorganic mercury compounds.

The good news is there is not a lot of sodium amalgam in nature. The bad news is that there are plenty of natural processes for forming dimethylmercury; see for instance Jonsson et al[1].


  1. Jonsson, S., Mazrui, N. & Mason, R. Dimethylmercury Formation Mediated by Inorganic and Organic Reduced Sulfur Surfaces. Sci Rep 6, 27958 (2016). https://doi.org/10.1038/srep27958
  • $\begingroup$ How quick is that reaction? If someone spills one on the other can it be cleaned up fast? Or should one assume its been created and treat it as worst case scenario? $\endgroup$
    – long4d99
    Mar 18 at 16:47

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