Potassium Permanganate

[Mumbles]

Congratulations, you're now on mod approval for 2 weeks. Say anything stupid like that again and you're banned indefinatly.

[leosedf]

I have almost 500g KMnO4, only made some silicone fuses with it.

In my country it's a bit difficult to find perchlorates, but i never made flash or anything else related to pyro with this.

Pretty nasty stuff!

[Mumbles]

We discussed this a bit more in chemistry the other day and just thought I'd pass on some info. I knew it was something like this, but I couldn't quite put my finger on it.

 

Anyway, the reason that MnO4- is so unstable is because of the extreme difference in electronegativity. Oxygen is extremely electronegative, and Manganese is not. The majority of the electron density lies in the oxygen, making the bonds unstable. The bond angles and shape make the molecule similar to ozone, and it reacts accordingly. It's oxidative potential is close to if not greater than that of ozone. This explains the high reactivity with organics, specifically ones containing pi bonds, in which case it can actually cleave the bond, releasing a large amount of energy and heat.

 

Perchlorate is much more stable due to it's electronegativity. It is comparable to that of oxygen resulting in a stable well distributed bond. This makes it much more stable, and less reactive, but actually containing more energy.

 

There, now you have your answer. I hope it shows how unstable it is, and you will never use it. The high electron density at the oxygens make it react way too easily.

[KevFla2001]

Thanks, I appreciate your help in trying to understand Kmno4.

 

If I follow you correctly, it's almost like a tug of war between the oxygen and manganese within the permanganate itself, making it unstable. Therefore it only takes a minor disruption in this balancing act to initiate a reaction, whereas Perchlorate, being much better balanced would require a more stronger disruption to initiate a reaction.

 

By coming to this site I have learned quite a few things about Kmno4 I couldn't find elsewhere.

 

Thank you

 

Kev

[Mumbles]

Well all covalet bonds are a tug of war. Think of Perchlorate like a 400lb guy against a 390lb guy. Fairly similar, pretty even. Now think of Manganese like weighing 150lbs. Not nearly as even, and oxygen would have a lot more of the rope on it's side. All reactions involve exchange of electrons. Oxygen in Permanganate has more electrons to use, than Perchlorate due to more being pulled toward it.

[Boomer]

So those are covalent bonds, that's why?

 

I always thought the bigger the difference in electronegativity the more stable the bond. That is then true only for ionic bonds, the high difference = high attraction makes the partners hard to separate again.

 

While e.g. substitution on aromatics works better if there's a partial charge due to one partner drawing the electrons closer.

[DeAdFX]

I think the only ionic bonding is between the potassium ion and the permanganate ion. However manganese is electronegative enough to form an ionic bond between Mn and O.

[Mumbles]

The bonds in permanganate are covalent. Even in MnO2, the bonds are more covalent than they are ionic. The transition metals do just that. Transition between ionic and covalent bonds. There is no magic line where on one side they make covalent and the other they make ionic. It is a transition.