Sciencemadness Discussion Board

edta and permanganate

andyloris - 23-11-2022 at 05:45

Hi, I tried mixing edta and potassium permanganate to see if I could make any manganese complexes. Instead of that, a very violent and exothermic reaction occured which produced an unknown green gas which smelled like chlorine.
I have no idea from where the chlorine comes.
Has anyone an idea of what could have occured ?

Thanks in advance.

Endo - 23-11-2022 at 06:36

A quick search yielded the following paper.

"Potassium permanganate oxidizes ethylenediaminetetraacetic acid (EDTA) to ethylenediamine-Ar,A',Ar'-triacetic acid (EDTRI)
and C02 in acidic (pH 3-5) perchlorate media."

"The overall EDTA-Mn04" redox reaction can then be represented by
6Mn(VII) + 5EDTA = 6Mn(II) + 5EDTRI + 10CO2

for which we expect theoretical yields of 1.67 mol of C02 and 0.83
mol of EDTRI/mol of Mn04". Lower yields for both products
in triplicate measurements indicate the occurrence of minor side

Were you doing your reaction in distilled water? If in tap water is there a chance you were getting chlorine from a side reaction with dissolved chloride or chlorine from a municipal water source?

Texium - 23-11-2022 at 07:12

Permanganate is not a good choice for forming complexes. In the permanganate ion, manganese is covalently bound to four oxygens. It is effectively a coordinatively-saturated, quite stable 16-electron complex. Therefore, there is no room for another ligand. The only way to make room for a ligand is by losing those oxygens, which can only be done by oxidizing something.

andyloris - 23-11-2022 at 08:00

I was doing the reaction in tap water. I'm going to try in distilled water.

Bedlasky - 23-11-2022 at 14:18

If you want to make Mn(III) EDTA complex, mix MnCl2, EDTA and KMnO4 solutions together.