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I wonder, what happens when sodium reacts with alcohol? What is the reaction mechanism?

I think that sodium is an electrophile that attacks the nucleophile oxygen atom in the -OH-group of the alcohol. Sodium will take one electron and bond with the oxygen molecule, while the bond between the oxygen and hydrogen will break. Am I correct?

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    $\begingroup$ Forms the sodium alkoxide and hydrogen gas. Its a standard way of making fresh sodium alkoxides with methanol/ethanol/propanols etc $\endgroup$
    – Waylander
    Feb 1, 2021 at 11:24
  • $\begingroup$ @Waylander - Have you ever done the reaction? I'm guessing that you'd have to do it under a blanket of nitrogen or CO2 to keep the alcohol from catching fire. $\endgroup$
    – MaxW
    Feb 1, 2021 at 11:51
  • $\begingroup$ @Waylander - Thanks, so the reaction mechanism that I guessed is correct? $\endgroup$
    – Csharpyikes
    Feb 1, 2021 at 11:51
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    $\begingroup$ @MaxW Many times. Depends on the scale, certainly under N2 for larger scale and with cooling as it is exothermic. Smaller scale in a f/c and just let the hydrogen bubble off. $\endgroup$
    – Waylander
    Feb 1, 2021 at 12:03
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    $\begingroup$ @Csharpyikes It is a moot point whether the nucleophilic alcohol is the attacking species as it is in solution and free to move around v the sodium is on the surface of a solid and immobile. $\endgroup$
    – Waylander
    Feb 1, 2021 at 12:05

1 Answer 1

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Sodium will not take one electron, as you propose. No, it is a redox reaction : the sodium atom will donate one electron to the Oxygen atom of the $\ce{ROH}$ alcohol, so as to repel one $\ce{H}$ atom and make an alkoxide ion. At the end, a $\ce{Na^+}$ cation and a $\ce{RO^-}$ alkoxide anion are produced in the solution. Of course the $\ce{H}$ atom will join the next $\ce{H}$ atom to produce $\ce{H2}$ bubbles that gets out of the solution. $$\ce{Na + ROH -> Na^+ + RO^- + \frac{1}{2}H_2}$$ The reaction is not dangerous. It will not catch fire if done in a sufficiently large amount of alcohol. I have done it plenty of times in the lab. No problem ! It is even a good way for getting rid of old residues of partially oxidized pieces of metallic sodium, in case you don't know what to do with them.

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