# Dissolving metal reductions

Could reduction of an organic compound by reacting it with sodium dissolved in $\ce{NH3}$ still proceed if a metal such as aluminium were used instead of sodium? I'm not sure about the aluminium amine or amide structure that would be formed.

• Aluminium does not react with anhydrous ammonia even at 500 degrees C. However I don't have a particularly good explanation why Al doesn't dissolve. It may be due to Al forming a thin protecting film on the surface; but from here it seems that the films only form when you have some water (so it's presumably Al2O3) You can dissolve Ca, Sr, Ba, Eu, and Yb in liquid ammonia, as well the alkali metals. All of these elements have relatively low ionization energies. – J. LS May 23 '15 at 16:13
• Thanks I wasn't sure some things work in theory but not in reality! – Technetium May 23 '15 at 16:19
• To me it seems, that aluminium is the odd one out. According to Yu Qiu, Lian Gao it seems that AlN is formed and ammonia is split. I only read the abstract though. I remember vaguely from when I tried the birch reaction, my lab colleague almost dissolved a whole iron/copper spatula by accident.| @J.LS Care to write up an answer. – Martin - マーチン May 25 '15 at 7:14
• What if aluminium amalgamate was used? Or if naoh and a nitrate salt were used with the regular aluminium? – Technetium May 25 '15 at 8:09

Is there a goal here? If you wanted to react aluminium with concentrated aq ammonia, you would get hydrogen but the rate would be proportional to temperature. However, this would be quite a poor way to create a reductive environment and as someone has already alluded, aluminium and sodium hydroxide or a strong mineral acid is better. From what I've seen, if you use alkali, a catalyst is needed. Ethylamine can be more conveniently used in place of ammonia. Calcium can also be used in reductions.I think I've also seen Indium, but that seems a bit expensive.

• The goal is to reduce a carboxylic acid or alcohol to the alkane using aluminium :) – Technetium Jun 16 '15 at 6:59

Sodium in anhydrous ammonia liberate a solvated electron for reductions and produce sodium amide.

If you do the same in the lab with aluminium then the chance is big that nothing would happen because the oxide layer on the aluminium surface and the fact that ammonia is a toxic gas that you don't smell at high concentrations.

Nothing will happen if you just put aluminium in aq. ammonia. You need to transform aluminium in another form with a strong acid to make it reactive.