# Does aluminium carbonate exist?

I read in a west African chemistry textbook (New School chemistry by Osei-Yaw Ababio) that aluminium trioxocarbonate (IV) (aluminium carbonate) does not exist. I need verified confirmations or oppositions.

• Trioxocarbonate(IV) = carbonate($\ce{CO3^{2-}}$). Aluminium carbonate($\ce{Al2(CO3)3}$) does not exist. However its basic form does exist in basic form as Dawsanite mineral. Check wikipedia. – Nilay Ghosh Jun 12 '17 at 13:48
• – Gaurang Tandon Jun 13 '18 at 9:49

It does not exist in nature, but you could make it in the lab by adding pressure.

From a traditional pencil and paper calculation I found the pressure needed for

Al2/3O (s) + CO2 (g) = Al2/3CO3 (s)

Or you could make an Al2(CO3)3 (aq) solution with concentration of $10^{-5}$ M.

Well, still not impossible. And there should be some special solvents and/or complex structures that easily allow this reaction (postulation).

• Could you add more detail, such as what pressure is required? Is there a specific procedure? – pentavalentcarbon Jun 12 '17 at 22:05
• I don't have the computational software I used to have. But you could calculate the free energy and find temperature/ CO2 pressure where the Al2(CO3)3 could be stable – High GPA Jun 12 '17 at 22:14

The reason why aluminium carbonate cannot exist is because it is simply too unstable and would rather be broken down instead.

Firstly, the aluminium ion is highly polarising with a high positive charge density (as it is a small ion which is triply charged). Thus, distortion of the carbonate ion's electron cloud is very great.

This is a very crude way of putting it but how the reaction happens is in fact in this manner: Aluminium ion "pulls" one of the oxygen atoms, which has a single bond to the carbon, in carbonate, towards it and that single bond breaks, allowing one of the other oxygens to form a double bond with the carbon. And this gives carbon dioxide.

Also, the reaction is favourable due to entropy considerations as well. The carbon dioxide formed is in the gaseous phase.

Thus, the reaction between aluminium and carbonate would gladly proceeds forward. This is why it "does not exist" as claimed by your textbook.

Hope this clarifies it.