guy
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Can iodine tincture be used for Al(Oi-Pr)3 synthesis?
I'm just wondering because I don't know if the synthesis requires water free conditions.
[Edited on 6/20/2007 by guy]
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not_important
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Do you mean Al(i-Pr)3 or Al(O i-Pr)3 ?
In the first case, the answer is no, in the second the answer is perhaps, but it will be iffy.
It's the usual problem - you've got to cut through the oxide film on the Al. The problem is made worse by the fact that aluminium alkoxides fall apart
in water, driven by the hydrolysis to insoluble Al(OH)3. So, maybe if you used a minimal amount of strong tincture, and extra Al which ends up as
sludge.
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guy
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| Quote: | Originally posted by not_important
Do you mean Al(i-Pr)3 or Al(O i-Pr)3 ?
In the first case, the answer is no, in the second the answer is perhaps, but it will be iffy.
It's the usual problem - you've got to cut through the oxide film on the Al. The problem is made worse by the fact that aluminium alkoxides fall apart
in water, driven by the hydrolysis to insoluble Al(OH)3. So, maybe if you used a minimal amount of strong tincture, and extra Al which ends up as
sludge. |
Ok. I read that I2 is pretty easy to extract from tincture. Let's say I use 10g of Al foil, how much I2 should I use? Will a whole bottle of
tincture be too much?
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hinz
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Use HgCl2 instead, it complexes the oxide surface better than iodine. You only need small amount of it, 0.1g or so. I once made alot of it, I used a
reflux condenser to keep the isopropanol in the flask, you only have to heat it in the beginning, afterwards the heat of the Al which get oxidised
will sustain the reaction if you wrap a piece of fabric around the flask fo isolation.
Don't forget to capture the hydrogen that comes out at the top of reflux condensor, you can make nice H2/O2 balloons from it
If you plan to do the Meerwein-Ponndorf reaction, it would be interresting to hear about it.
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guy
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I used solid iodine and 99% Isopropanol and Al foil. I used 10g of Al foil, 150mL i-PrOH, and a tincture's worth of pure iodine. I heated to boiling
for about 10 minutes and nothing happened. What is wrong?
Edit:
Pshh.. Apparently I need both HgCl2 AND I2. Where the hell am I going to get super toxic mercuric chloride?
[Edited on 6/21/2007 by guy]
[Edited on 6/21/2007 by guy]
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guy
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I tried adding some CuCl2*2H2O to some 99% isopropanol and a bit of I2. Not much happened. I heated it to boiling and copper metal precipitated out.
There was bubbling but I could not tell if it was the boiling or H2. I removed it from heating and only it stopped bubbling except for some tiny
bubbles occasionally. Could I be onto something?
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hinz
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The trick of HgCl2 is that it dissolves al tiny bit of Al (the HgCl2 gets reduced to Hg by Al). The Al-amalgam can't form a protective oxide layer, so
it can react with Ipr-OH.
The Cl- from CuCl2 somehow complexes the oxide layer too, but I'm not sure how much. I once made an interesting experiment in school, I added Al foil
to CuCl2 and CuSO4 solution, in the CuCl2 the Al got oxidised, in the CuSO4 soln. nothing happened, so the Cl- somehow attacks the oxide layer too.
If this still don't help, you can put some quartz sand together with the Al-foil in a flask and stirr it, the quartz sand will then scrap off some of
the Al2O3 on the surface so that the Ipr-Oh can react with the oxide free Al.
I think there are some threats about HgCl2, you can get mercury from switches, thermometers and as HgS as zinnober-pigment.
Dissolve some Hg in hot HNO3 and add some HCl. Then you boil it down and voila your HgCl2.
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not_important
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Gallium works, too.
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Eclectic
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Also that 1% water in your 99% IPA is a real show stopper. If you have some molecular sieves, or silica gel, you can dry 50ml or so, make some
aluminum isopropoxide with that, the use what you have made to dry the remainder of your alcohol.
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guy
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| Quote: | Originally posted by Eclectic
Also that 1% water in your 99% IPA is a real show stopper. If you have some molecular sieves, or silica gel, you can dry 50ml or so, make some
aluminum isopropoxide with that, the use what you have made to dry the remainder of your alcohol. |
I can easily make anhydrous magnesium sulfate or copper sulfate. Would that work?
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