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Nicodem
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Quote: Originally posted by Cloner  | | Using isopropanol, aluminum foil, mercuric chloride and iodine crystals (the latter two in catalytic amounts) I am trying to prepare aluminum
isopropoxide. The reaction seems to proceed but at some point the hydrogen evolution stops. |
You either use mercuric chloride or you use iodine. I can't see how using both would improve anything. Anyway, you don't give the experimental and
provide no references, so don't expect a reasonable answer. Potential issues can be poor stirring, wet isopropanol, overconcentration, impurities in
aluminium, too low temperature, whatever else...
| Quote: | | Can atmospheric water be the problem? I have no idea how sensitive this reaction is to water and in what manner water disturbs it.
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Atmospheric water no, but water in the solvent quite likely. The reaction should not be terribly sensitive for small amounts of moisture, as far as I
know, but more water will surely disturb the reaction.
| Quote: | | The IPA is dry to begin with (sodium was dissolved in it, then it was distilled). |
I guess you never read Vogel's? Have you ever heard about the isopropanol/water azeotrope? Check the complete equation of sodium reacting
with water in isopropanol as the solvent and you will see that the water is not removed from the system during this reaction (its available
amount remains exactly the same, only its concentration drops somewhat). You would have done a much better job by drying it over calcium sulfate or
similar.
…there is a human touch of the cultist “believer” in every theorist that he must struggle against as being
unworthy of the scientist. Some of the greatest men of science have publicly repudiated a theory which earlier they hotly defended. In this lies their
scientific temper, not in the scientific defense of the theory. - Weston La Barre (Ghost Dance, 1972)
Read the The ScienceMadness Guidelines!
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Nicodem
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6-8-2011 at 14:26 |
Cloner
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First and foremost, I am using iodine and mercuric chloride because everyone else is doing it, same for drying over sodium. This may sound like a
terrible reason, but I don't understand the mechanics well enough to make adaptations to a procedure that apparently works well for others.
The procedure is pretty simple. Add mercuric chloride, iodine and aluminum foil cuttings to isopropanol and let it reflux. I used 2.0 g aluminum and a
few grains of both catalytic agents in 40 ml IPA. I used a magnetic stirrer/heater.
The reaction starts off without any doubt (hydrogen evolution. The reaction takes place even if not under reflux conditions). There is a discoloration
to greyish. As the reaction proceeds, the mixture gets greyer and greyer, but the aluminum foil does not disappear. The reaction seems to stop
halfway.
This is why I wonder if water entry is the culprit, or there is another reason for failure. It's definitely not like starting and maintaining a
Grignard.
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hosko
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Removed cross-post. Multiple posts won't help you getting better answers or getting answers in less time. Please continue the discussion over here:
http://www.sciencemadness.org/talk/viewthread.php?tid=15104
[Edited on 23-10-11 by woelen]
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Paddywhacker
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After distillation, what is the best way to store the product?
I can imagine it forming a solid lump in whatever bottle or jar that is used, and that would make it difficult to use later. Would someone who has
prepared it please give their opinion on storage.
Thanks
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Alkoxide
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Aluminum Isopropoxide issues
Today was my first attempt at synthesizing aluminum isopropoxide. The reaction didn't go as planned. I've read over several synthesis methods and
decided to use iodine only as my catalyst. Typically this reaction is done with mercury chloride, but I'm not comfortable working with mercury
compounds. This reaction can also be performed with carbon tetrachloride (synthesis found in Vogels).
Reagents used:
2-Propanol, 99% - United Nuclear
Iodine - synthesized from KI
Aluminum - shoprite brand aluminum foil
Procedure:
A 1 liter 3 neck round bottom flask was charged with 150mL 2-Propanol, 13.5g of aluminum foil (cut in small pieces), and 0.4g iodine. . A 600mm Liebig
condenser was used for refluxing. A drying tube with anhydrous calcium chloride was mounted on top of the condenser. The flask was heated with a hot
plate on medium heat to achieve refluxing. The mixture refluxed at a constant 78 degrees Celsius. The iodine crystals dissolved in the 2-propanol,
forming a deep red solution. After about 15 minutes of refluxing, this solution began to lighten in color and eventually became clear. After 1 hour of
refluxing, it appeared that no significant amount of aluminum had reacted. An additional ~0.5g of iodine was added to the flask in hope of increasing
the reaction rate. The solution turned deep red again and became clear within 10 minutes of the addition. Again, approximately 0.5g of iodine was
added to the flask with color changes in the same manner as the previous addition. After an hour and 40 minutes of refluxing, no significant amount of
aluminum had reacted.
At this point I removed the hotplate and cleaned my apparatus. I removed the unreacted aluminum from the reaction mixture and I have the remaining
liquid stored in a 500 mL media bottle. The liquid is a faint yellow color, most likely from traces of iodine.
I'm a little stuck as to where I went wrong. I found an old thread here on aluminum isopropoxide and there was someone who successfully used the
iodine only method. I'm thinking that my reaction problems may have been possibly due to water in the 2-Propanol, impurities in my iodine, or maybe
not using enough iodine catalyst. I was able to find a literature reference for an iodine only synthesis but it is not in the public domain so I could
not physically obtain it. Does anyone have any ideas for how I should go about a second attempt at this reaction?
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Nicodem
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13-5-2015 at 12:47 |
byko3y
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In your case, iodine generates some amount of isopropoxide, but then the reaction ceases.
As far as I know, the only method that allows the production of aluminium isopropoxide without using a large amount of aluminium halides or mercury is
described in the patent US3305571. The idea is about activating the aluminium using a lot of pre-made aluminium isopropoxide, and then incrementally
adding a new aluminium as fast as the old one is consumed. But I have no idea about whether it works or not.
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Alkoxide
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| Quote: Originally posted by byko3y | In your case, iodine generates some amount of isopropoxide, but then the reaction ceases.
As far as I know, the only method that allows the production of aluminium isopropoxide without using a large amount of aluminium halides or mercury is
described in the patent US3305571. The idea is about activating the aluminium using a lot of pre-made aluminium isopropoxide, and then incrementally
adding a new aluminium as fast as the old one is consumed. But I have no idea about whether it works or not. |
I skimmed through the patent. It seems interesting but you need some of Al(i-PrO)3 to start the reaction, which I don't have (or at least
not much of it). Here is the link to the literature reference for the iodine synthesis method (for anyone that may have access):
http://en.cnki.com.cn/Article_en/CJFDTOTAL-DLTD200703020.htm
I wish this reagent was available to hobbyists. There is a Japanese seller on ebay that has it but I wouldn't want to deal with customs. Maybe in the
future I'll try the carbon tetrachloride method from Vogels. For now though, it would be nice to be able to get this working with iodine, I have a few
grams left over from this attempt.
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byko3y
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I see you didn't mention the dehydration of isopropanol. Isopropanol can contain significant amount of water.
Have you read this article? Because I don't have access, neither I can understand the text on the site which is written in chinese.
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Alkoxide
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The isopropanol is supposed to be 99%. I wasn't sure if 1% water would have an effect on the reaction. Would you recommend drying the isopropanol
further? I was not able to read the article, I just posted it on the off-chance that someone here had access to it.
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byko3y
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My isopropanol also was supposed to be 99%, until I figured out it's not isopropanol at all ^_^.
You used 1.5 mmol of iodine for 2500 mol of isopropanol. I hope you understand that 1% of water is actually 3 molar %, which is something like 80
mmol.
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Alkoxide
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When you put it in terms of molar percent, the amount of water present seems much more significant. As a starting point, I will dry my isopropanol
further with Calcium Oxide before retrying the reaction. Maybe more iodine catalyst as well for the next try?
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byko3y
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Once again: have you read the article you linked? Because you try to perform some procedure, and I have no idea about whether it was ever successfully
performed. You might need something like 10% mol of iodine, but once again - I don't know. You might need to gradually add aluminium and isopropanol
as the old one is consumed, and once again - I dont know.
Halogenes are capable of oxidizing alcohols, so your isopropanol could be simply turned into acetone, leaving HI as a product, which is useless for
aluminium activation AFAIK.
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Alkoxide
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I haven't read it, I don't have access. Panziandi made Al(i-PrO)3 with iodine instead of mercury chloride on the first page of the thread. He didn't
mention how much iodine he used though. At the top of this page Nicodem suggested using either iodine or mercuric chloride. It seems like this method
may have been feasible. Also, I would think halogens are more reactive toward metals than alcohols. In my attempt the iodine reacted with something ,
most likely the aluminum (loss of iodine red color in solution).
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byko3y
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He does not describe the procedure and he "thinks" that he did not use mercury. Nicodem also has no idea about practical conditions, as far as I see,
because in most procedures you will see HgCl2 + I2 and he doesn't seem to realize that.
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Pumukli
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For those who may find it useful:
excrept from A.L.Wilds "Organic reactions", 1944. vol 2. p.178.
reprinted in Hilgetag - Martini - Weygand "Preparative organic chemistry" page 48, this later can be borrowed from the SM library. :-)
....................................................
As an example here follows the preparation of aluminium isopropoxide, which is the reagent most commonly used: (- used for MPV reductions, it is in
that part of the book - Pumukli)
Aluminium wire (27g, 1mole) or foil is cleaned with emery paper, then with a cloth and placed in a 1-litre round bottomed flask containing anhydrous
2-propanol (300 ml) and mercuric chloride (0.5 g). The flask is fitted with a reflux condenser and CaCl2 tube. The mixture is then heated to the
boiling point on a water bath. When the boiling begins carbon tetrachloride (2ml) is added through the condenser. The mixture becomes brown and in a
few minutes vigorous evolution of hydrogen begins. Heating is then interrupted and the rection is controlloed by cooling in ice-water. When the
reaction moderates, heating is continued until all the aluminium is dissolved (6-12 h). The hot solution is transferred into a distillation flask, the
propanol is removed under slightly diminished pressure, and the aluminium isopropoxid is distilled in a vacuum (oil bath temperature 180-190 C) It is
a colorless, viscous liquid of b.p. 130-140 C/7 mm, or 140-150C/12 mm.
Aluminium isopropoxyde can be kept in substance or in solution in glass-stoppered flasks sealed with parrafin. For many purposes it is unnecessary to
distill the reagent and the dark solution obtained on dissolution of the aluminium can be used directly.
Detailed directions for the preparation of aluminium ethoxide and butoxide are given in Organic Syntheses.
.............................................................................................
Forgot to write that the above book says that the activation of aluminium can be done either by HgCl2 or iodine too.
[Edited on 14-5-2015 by Pumukli]
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WGTR
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Aluminum isopropoxide prepared by various methods
Includes effects of catalysts such as HgI2, HgCl2, I2 and FeCl3.
Attachment: Synthesis of aluminum isopropoxide from aluminum dross.pdf (2.1MB)
This file has been downloaded 966 times
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byko3y
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Trying to make aluminium isopropoxide from 4 g of Al turnings + 35 ml of IPA dried by passing it through activated 4A sieves lying on a filtering
paper in a buchner funnel. Not the best way to dry, but anyway my IPA was supposed to be pure already.
0.1-0.2 g of iodine was added as a catalyst. After 20 minutes of heating I've added 0.2 g of NaCl. Refluxing for an hour already, nothing happens, the
mixture is the same yellow iodine-colored IPA with Al turnings in it. I can see IPA boiling, but no signs of hydrogen.
I'm starting to think the article above is just another BS. But i thought guys in the south korea have a lot of equipment and are supposed to do a
real work, because they have a lot of chemical industry plants and stuff like that.
BTW, "the mixture gets greyer and greyer" - this means your aluminium turns into Al(OH)3.
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blogfast25
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| Quote: Originally posted by byko3y | After 20 minutes of heating I've added 0.2 g of NaCl. Refluxing for an hour already, nothing happens, the mixture is the same yellow iodine-colored
IPA with Al turnings in it. I can see IPA boiling, but no signs of hydrogen.
|
If your iodine isn't reacting with the Al turnings then the latter will not react with the IPA either.
I don't know what's the problem with your Al but I would bet good money it's the cause of your failure.
At a very minimum, try and react some of your turnings with a bit of that same iodine, in a test tube. You should get a vigorous reaction that starts
even at room temperature:
https://www.youtube.com/watch?v=0PxQwff4xoQ
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byko3y
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blogfast25, you can clearly see in the video that no reaction happens at r.t., and they needed to heat the mixture until iodine started to sublime,
which is way over 100°C, while my reaction barely reaches 80°C.
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blogfast25
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| Quote: Originally posted by byko3y | | blogfast25, you can clearly see in the video that no reaction happens at r.t., and they needed to heat the mixture until iodine started to sublime,
which is way over 100°C, while my reaction barely reaches 80°C. |
I'm beginning to think you're an idiot who doesn't even want any help. There's no heating going on, other than REACTION HEAT (the exotherm). It's so
exothermic iodine starts subliming.
Search for 'aluminium iodine' in the Utoob search box for plenty examples. It's a very well known reaction.
In this one all it takes is a few drops of water:
https://www.youtube.com/watch?v=SKSU72-1ERc
MrHomeScientist (author of the video) is a member here: U2U him if you like.
Should in your case you're not getting a reaction, then by all means add a little GENTLE heat.
[Edited on 18-5-2015 by blogfast25]
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WGTR
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I tried this reaction with iodine, not with preparative intentions, but just to see what would happen. So how fresh are your aluminum turnings? The
more oxidized they are from air or moisture, the harder it will be to get things going.
I took some 6061 aluminum, and ground it to powder with a fine file. This powder was placed into 100% IPA that had been sitting out for some months
in a squeeze bottle. It most assuredly had moisture in it. This was placed in a small glass bottle and capped. A couple of small iodine grains were
added, and the mixture was shaken to dissolve the iodine.
Nothing seemed to happen at this point. The iodine gave a yellowish color to the clear solution. Since sluggish Grignards can be started with
ultrasonic agitation, I tried agitating the glass bottle in the ultrasonic tank for a few minutes to see if a spontaneous reaction would occur.
Nothing seemed to happen, at least not at room temperature.
I took the sealed bottle, and then bravely heated the bottom with a heat gun. As an aside, it is not a good idea to heat a sealed bottle of flammable
liquid with a heat gun. In this fortunate case, the IPA refluxed inside the bottle, as planned, and didn't crack from the heat stress. Once the
contents were nice and warm, I took the bottle back to the ultrasonic tank. Finally, I did see some reaction occur. This was manifested as a gradual
change in solution opacity. The aluminum did not appear to be noticeably dissolving, but the gradual change in opacity was obvious over time. Now,
sitting in the lab at room temperature for several days, the solution is quite opaque and brown. The aluminum powder looks to be about the same
amount, but it's like there is a colloidal suspension of something in the IPA. Every day or so I go by and give things a shake.
The reaction products that resulted from the aluminum and iodine were getting hydrolysed apparently. I would say not to underestimate how clean the
aluminum should be (free from oxides), and how dry the IPA needs to be. Some ultrasonics in a heated tank may be needed to keep the reaction going,
at least until everything is bone dry.
YMMV
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Pumukli
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"I would say not to underestimate how clean the aluminum should be (free from oxides), and how dry the IPA needs to be."
I agree. Although I don't have first hand experience with this reaction but the recipe I typed in a few days ago calls for anhydrous isopropanol. (It
is not in the recipe but I seem to recall that they achieved the anhydrous state by distilling isopropanol TWICE from CaO. It may be in another
reaction but they definitely not just took a bottle from the shelf and used it.)
Another thing is the rate of dissolution of Al. In that above mentioned recipe they reported 6-12 hours was required for the disappearance of 1 mole
of Al, while the reaction was vigorous! And they cleaned the surface of the Al wire at first.
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blogfast25
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| Quote: Originally posted by WGTR | | Now, sitting in the lab at room temperature for several days, the solution is quite opaque and brown. |
Brown??? That's not quite what you'd expect either! 
[Edited on 18-5-2015 by blogfast25]
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Pumukli
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Actually a dark solution is expected.
Whether it is dark brown or dark black or dark purple I don't know but it should be something dark. :-)
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blogfast25
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Expected on what basis? Aluminium isopropoxide is supposed to be colourless. So is AlI<sub>3</sub>. So what is supposed to provide any VIS
absorbance here?
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