Triazine
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Preparation of Potassium Ferricyanide
I'm using K3Fe(III)CN6 and KOH as an oxidant for a reaction, but I'd like to make my own on scale to save money. It seems like
it be as easy as adding 6 eq KCN to FeCl3, but I can find zero references for this procedure.
Every source oxidizes ferrocyanide instead. I'd rather work with solid KCN than chlorine, bromine, or cyanide gas, and using a solid oxidant like
K2MnO4 would require tedious purification.
Are my instincts right, or am I over looking something?
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woelen
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That reaction could work, but its not as clean as you may expect. There will be side reactions, such as formation of (CN)2 and formation of HCN. I
tried the reaction myself (using NaCN instead of KCN, but that does not really matter) and you don't get a nice clear solution of ferricyanide if you
mix cyanide and ferric chloride in the right stoichiometric ratio, but some turbid solution. You need to add excess KCN in order to get a clear
solution. From that you need to isolate the K3Fe(CN)6.
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blogfast25
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Are you sure you need hexacyanoferrate (III)? It's a very, shall we say, 'exotic' choice of oxidiser...
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Triazine
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Thanks woelen! That really makes synthesizing my own a whole lot less attractive; I really don't want to deal with HCN or cyanogen.
@blogfast25: For my purposes it probably is. I'm oxidizing a diarylmethane to the quione methide (gives a beautiful yellow color). There might be
small molecule oxidants that would work, but an advantage of the potassium ferricyanide is that its a biphasic reaction which really helps with
purification. I've gotten the reaction to work with 2eq silver(I) oxide too, but that gets really pricey. I think cerium(IV) ammonium nitrate should
also work, but haven't tried it yet and I think it's more expensive too.
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blogfast25
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Quote: Originally posted by Triazine  | | I think cerium(IV) ammonium nitrate should also work, but haven't tried it yet and I think it's more expensive too. |
Ah, but it's probably easier to home synthesise, than K3Fe(CN)6. As a polishing powder, CeO2 is quite OTC.
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