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Easy question to kick off my chemexchange membership!

I'm learning chemistry in my spare time, and fittingly for a video art project I'm doing, decided to try a simple inorganic(?) procedure to make some crimson flames.

My research lead me to believe that lithium methoxide works wonders for this, especially in solution with methanol which only has a very faint blue flame on its own. I basically already know it works, based on some demonstrations seen on YouTube, but I'm unable to find much anything in literature about the lithium salt of methanol. So I'd like to verify my understanding of the equation:

To my understanding, dissolving lithium metal in methanol should yield:

$$\ce{Li + CH4O -> CH3LiO + H}$$

...Lithium methoxide in solution with methanol, assuming an excess of methanol, and some released hydrogen gas.

Am I correct? Can someone shortly explain the actual reaction that takes place?

Additionally: I think the solution should be relatively stable and easy to store and handle, like methanol, unless there's a reason to believe otherwise? Also, if one wanted to produce dry lithium methoxide powder from this, what might be a good precipitant to crash it out of methanol?

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    $\begingroup$ You are basically correct. As with the other group I metals lithium reacts with proton sources such as alcohols and water to give hydrogen and the metal salt. This may be useful to you orgsyn.org/demo.aspx?prep=cv6p0795 $\endgroup$
    – Waylander
    Commented May 12, 2018 at 20:03
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    $\begingroup$ You are aware that methanol is rather toxic and easily penetrates your skin? And that this reaction you are thinking of is quite vigorous and can easily lead to an explosion with air of the H2 produced? $\endgroup$
    – Karl
    Commented May 12, 2018 at 21:58
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    $\begingroup$ @Karl I should probably have clarified that eventually setting fire to some amounts of the solution is obviously an entirely separate thing! Of course, the dissolving has to be done in a fume hood with proper exhaust and have fire nowhere near it. I will edit my question to rectify the misunderstanding. As for methanol, yes, I follow good lab practice and generally try not to pour solvents (or anything, really) on myself. I do appreciate the concern though. If there's something I've yet overlooked, let me know. $\endgroup$
    – untitled8468927
    Commented May 13, 2018 at 15:03
  • $\begingroup$ @Waylander thanks! I haven't worked with alkali metals before. $\endgroup$
    – untitled8468927
    Commented May 13, 2018 at 15:03
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    $\begingroup$ And be also ware, methyl- and methoxy- inorganic compounds are notoriously toxic, flammable and explosive. Something as light as lithium is fairly benign, but many aspiring and successful chemists have perished exploring the methyl-metal world. $\endgroup$
    – Stian
    Commented May 14, 2018 at 20:48

1 Answer 1

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I have not done it with lithium but many times with sodium. Lithium is the less reactive, so it should not give more problems. We use sodium to dry methanol, so it is a common operation in the lab. The reaction is:

$\ce{2Li + 2CH3OH -> 2LiOCH3 + H2}$

Of course, hydrogen is dangerous, especially in the presence of oxygen and still more in this exothermic reaction. So, be careful.

The solution is stable, but attracts water and carbon dioxide, so it must be stored well closed.

To get dry lithium methoxide, the easiest is just to evaporate the excess of methanol. You put it in a round bottomed flask, attach it to the rotary evaporator, open the vacuum and distill it of. With sodium it works perfectly well. A white solid remains. Again, this solid will attract water and carbon dioxide, so it must be stored properly.

Finally, if the only purpose is to have a methanolic solution of lithium, you can better use lithium chloride which is very soluble in methanol, and much safer (no reaction, no hydrogen, no heating).

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