mfilip62
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NaI best method?
Hi guys,
I am having trouble doing Finkelstein swap using KI.
NaI is best for this reaction since NaI solubility in acetone is much greater than solubility of KI.
Is there known and symple procedrue taht works well where you can use KI and NaX to get KX and NaI by ion exchane!?
I also thought about generating HI gas using KI and H2SO4 and bubbling it into NaCO3 or NaOH.
I know it's not very hard to get but does anyone know realy simple and efficient method!? Iodide are expensive and scarce here...
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Mixell
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You need a to find an anion that forms a highly soluble salt with Na and a lot less soluble salt with K.
I haven't found such halides that have distinct solubilities between their Na or K salt.
But NaNO3 solubility is 730 g/L (0°C) and KNO3 is 133 g/L (0 °C) I think thats distinct enough.
Now, I'm not sure about the following procedure, but maybe it could work: Take a flask with the needed amount of water, cool it to 0C and dissolve KI
in it (to saturation). Heat it up to 70-90C and dissolve the molar equivalent of NaNO3. Wait it to cool to a safe temperature and freeze it again to
0C. most of the KNO3 should drop out of solution, and you will remain with a solution of NaI.
But you will still have some potassium and nitrate ions in your solution. I don't know about KNO3/NaNO3 solubility in acetone, but you could evaporate
the solution and try to dissolve the solid in acetone (get information on KNO3 and NaNO3 solubilities in acetone beforehand). And if the nitrate
anions will not affect your reaction or end product, you could ignore them.
Edit: Maybe you could find a replacement for the nitrate on this page: http://en.wikipedia.org/wiki/Solubility_table .
[Edited on 29-4-2011 by Mixell]
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Mixell
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Oh, lucky you (if Wikipedia does not lie): NaClO4 solubility: 167g/100ml 0C and KClO4 solubility 0.76g/100ml 0C.
There is a chlorate option too, but the differences are smaller than the perchlorate's (check the table).
So check out which of the anions does not affect your reaction or is insoluble in acetone.
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mfilip62
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Thanks Mixell,
I know how this technique works in general,I done it befroe,I am just asking if someone did same to get NaI and how good are they jields.
Lucky me...not! If I could only get KClO4 or NaClO4 here!
Looks like HI+NaOH technique is alos something to avoid since HI would eat my expensive glassware.
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Mixell
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HI attacks glass? Your not confusing it with HF?
So do the nitrate method if it doesn't interferes with your reaction...
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mfilip62
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I probably did...but still,problem is that H2SO4 alone will oxydize I- to I2 and I don't have phosphoric acid...
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ldanielrosa
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Why not oxidize KI to elemental iodine with H2O2 and HCl, wash, and recombine with NaOH for the salt you need: NaI?
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mfilip62
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I have elementar I2.
You mean you can simply react it with NaOH!?
How!?
I got another idea,but don't know if this one is even plausible,what you guys think:
Take 1mol KI and 1,1mol NaCl,dissolve both in minimum ammount of water.
Add acetone,most of the KCl should crash out and most of NaI should stay in acetone/water.
Filter it,washing filter cake with some more acetone.
Combine filtrate and washes,add just enough Na2SO4 to filtrate unitil it no more clumping is observed (Na2SO4 sucks up water).
Rest of the KCl and some NaCl should crash from the acetone,filter again,discard the cake and evaporate acetone to get NaI.
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Sedit
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That will give you a mixture of Iodide and iodate. You can reduce the Iodate with carbon or heat.
Knowledge is useless to useless people...
"I see a lot of patterns in our behavior as a nation that parallel a lot of other historical processes. The fall of Rome, the fall of Germany — the
fall of the ruling country, the people who think they can do whatever they want without anybody else's consent. I've seen this story
before."~Maynard James Keenan
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ldanielrosa
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Myst32yt shows it pretty well at http://www.youtube.com/user/myst32YT#p/u/17/HKWvgfMhmUI
Just use NaOH instead and you'll get NaI.
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mfilip62
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Interesting! But problem is that he adds liberal ammounts of hydroxide to unknown concetration of I2.
I will do the opposite...
Make known concetration of NaOH in water and add elementar I2 with stirring until no more dissolves/clor change.
Cool it to percipitate insoluble NaIO3 and get NaI from solution.
Problem with his method is that leftover hydroxide contaminant will wreck the main reaction.
I allready done this reaction using Cl2 and KOH to get KClO3 and KCl.
[Edited on 2-5-2011 by mfilip62]
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Mixell
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Iodine dissolves in water in the presence of of iodide ions, they form the I3 1- anion (triiodide).
Better use stoichiometric amounts.
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mfilip62
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I know about triiodide thing,that is how tinctures are made.
I think that best way is to use stoichiometric ammounts,mabe just a little bit more I2
in hot solution of NaOH while stiring.
If there is some NaOH left I would use any HX acid to get pH=7,evaporate the water
and dissolve remaining solid in acetone,filtrate,than evaporate acetone using heat.
Some NaIO3 that is formed during this reaction will react with acetone while heating
to produce NaI.
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