Sciencemadness Discussion Board

Preparation of solid aluminium isopropoxide

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Klute - 18-9-2009 at 18:14

I'm planning on trying out an Oppenauer Oxidation to prepare a few aromatic aldehydes. The most common and availble catalyst is aluminium isopropoxide.

The "classical" conditions of the Opennauer oxidation, using exces acetone as oxidant and a co-solvent, can't be used here, as the formed aldehydes xould immediatly condense with acetone in an aldol reaction. So another oxidant, non-enolizable, such as paraformaldehyde is used.

So the reaction requires solid aluminium isopropoxide in toluene to be used as a catalyst, as described in this OrgSyn prep.

So I was considering preparing the isopropoxide myself, following the details given in the preparation of alumium butoxide.
Now the problem is that usually the aluminium isoproxide is isolated by distillation, after removal of excess isoproyl alcohol. Unfortunaly, my vaccum facilities don't able me to distill this product at a reasonable temperature (bp= 140–150 °C at 5 mm Hg). And I don't feel confortable adding water to the prepared alkoxide solution to effectively filter out the impurities in the aluminium, mercury, and unreacted meatl. Actually, I don't feel confortable filtering that bloody mercury, and I'm scared the solution might be exposed to too much humidity during the filteration ( the atmosphere in my soon-to-be new lab is quite humide).

So basicly, my question is, do you think I cna use the crude alkoxide directly in the reaction? Will the mercury and undissolved impurities interfere with the oxidation?

I don't want to prepare the catalyst freshly before each run, as I plan on doing sevral small scale test, and each preparation of the alkoxide requires several hours of reflux.. So I was thinking of making a large batch and using the catalyst when needed.

Of course, all this could be simplified by simply buying commercial aluminium isopropoxide. It's cheap, and availble in 100g quantities. The problem is that "old" alkoxide is under the form of less soluble tetramer, as opposed to fresh which is a readibly-soluble trimer, so the catalyst might be less effective..
EDIT: Found a very complete document on the Oppenauer oxidation, stating that the solid tetramer can be converted to the liquid trimer by heating it, and that the two forms are equally as effective for the oxidation! Very nice read: Oxidation of alcohols to aldehydes and ketones

Basicly, I'd like to know if anyone has experience with preparing alumium alkoxides from alumium amalgam, and isolating the alkoxides. Also, if anyone have already performed a Oppenauer oxidation, even a "clasical" one, would you care to share details and comments?

Thanks in advance!

[Edited on 19-9-2009 by Klute]

sonogashira - 19-9-2009 at 09:51

http://www.sciencemadness.org/library/books/Preparation_of_O...

Look on page 7 for an easy preparation - and the phrase "the product may be used directly for subsequent reactions" might be interesting to you! :D

Klute - 19-9-2009 at 13:55

Thanks for the ref, nice book! But unfortunaly I can't use it as is, I have to remove the ispropyl alcohol if I want the reaction to occur.. The formed iPrOH (and MeOH from paraformaldehyde) must be distilled out to favor the equilibrium.

Vogelzang - 20-9-2009 at 05:26

See

https://www.hyperlab.info/inv/index.php?s=88e1ebf6d308224ea5...

benzylchloride1 - 20-9-2009 at 14:09

I once prepared a small amount of aluminum isopropoxide and I was able to distill a good part of it at water pump pressure. I followed the procedure in Vogels and when I distilled the excess isopropyl alcohol, crystals formed in the distillate indicating the codistillation of the isopropoxide with the isopropanol. The were highly water reactive and would react violently with water. I wonder in aluminum isopropoxide could be used instead of sodium ethoxide or methoxide as a strong base in deprotination reactions? Vogel also claims that after forming the aluminum isopropoxide, the crude material can be diluted to 1L with isopropanol and used as such for reductions. Another idea; add a small amount of water to the mixture, forming collodial alumina which will carry the mercury, and suspended impurities with it. Filter and strip the excess isopropanol with a rotary evaporator with the vacuum source protected with a calcium chloride tube and use the aluminum isopropoxide as is. I am planning on making some aluminum isopropoxide once I finish drying my isopropyl alcohol.

[Edited on 20-9-2009 by benzylchloride1]

panziandi - 20-9-2009 at 16:22

Aluminium isopropoxide is easily made, it was one of the first "organometallics" I made. I followed a standard procedure (I think it was Saunders & Mann), we are talking me about 14 here! I think I used I2 instead of HgCl2! So consider that! If you use a excess of iPrOH and distill that off, you could use the residual Al(iPrO)3, or use the alcoholic solution as is.

I wonder too if it could be used as a base... certainly would be much more convenient (and cheaper) than sodium (m)ethoxide for most amateurs. I suppose Al(MeO)3 maybe equally convenient, perhaps better, as a base. Can anyone get a pKa?

Arrhenius - 20-9-2009 at 17:55

All alkoxides are basic. This is dependent upon the alcohol they come from. pKa is the acidity of the conjugate acid... so.. the pKa should be ~16. Given its ability to be a reducing agent in the presence of isopropanol, it may be more difficult to control this reagent as a base. Solubility and the fact that aluminum is chelating might also be a problem. I2 is a fine way of initiating the reaction of alcohols with magnesium or aluminum.

benzylchloride1 - 27-9-2009 at 21:02

I am working on synthesizing some aluminum isopropoxide following the procedure in Vogels Text Book of Practical Organic Chemistry. I followed their procedure and after 6 hours of refluxing, very little of the aluminum had dissolved, but the mixture had turned quite dark. The 91% 2-propanol that I used was treated with sodium chloride and decanted from the brine that formed. The 2-propanol was then dried over anhydrous magnesium sulfate before using. The aluminum was aluminum foil cut into small pieces. 0.5g of mercuric chloride was added to the mixture. Some bubbling was observed after heating to reflux and the mixture turned very dark in color and dark spots formed on the aluminum, but even after 6 hours of refluxing, very little of the aluminum had dissolved. I am starting over with this synthesis, and drying the 2-propanol by a different way. After treating the 2-propanol with sodium chloride, I am then refluxing the alcohol with calcium oxide and distilling. What can I do to further dry the alcohol as it appears that the alcohol must be completely anhydrous for the reaction to occur?

Magpie - 27-9-2009 at 21:09

I use 4A molecular sieves to dry the azeotropic ethanol I distill from vodka. That should work well for polishing your IPA also I would think.

Edit: correction: I use 3A mole sieves

[Edited on 28-9-2009 by Magpie]

UnintentionalChaos - 27-9-2009 at 21:23

Quote: Originally posted by benzylchloride1  
I am working on synthesizing some aluminum isopropoxide following the procedure in Vogels Text Book of Practical Organic Chemistry. I followed their procedure and after 6 hours of refluxing, very little of the aluminum had dissolved, but the mixture had turned quite dark. The 91% 2-propanol that I used was treated with sodium chloride and decanted from the brine that formed. The 2-propanol was then dried over anhydrous magnesium sulfate before using. The aluminum was aluminum foil cut into small pieces. 0.5g of mercuric chloride was added to the mixture. Some bubbling was observed after heating to reflux and the mixture turned very dark in color and dark spots formed on the aluminum, but even after 6 hours of refluxing, very little of the aluminum had dissolved. I am starting over with this synthesis, and drying the 2-propanol by a different way. After treating the 2-propanol with sodium chloride, I am then refluxing the alcohol with calcium oxide and distilling. What can I do to further dry the alcohol as it appears that the alcohol must be completely anhydrous for the reaction to occur?


It takes a vast quantity of MgSO4 to strip out that 9% water effectively. Attached is a much simpler way to do it.

After that, you could proceed with MgSO4, reflux with magnesium turnings, or molecular sieves.

anhydrous iPrOH.jpg - 133kB

Arrhenius - 27-9-2009 at 21:45

If that paper's right, and you can even slightly overshoot the azeotrope by drying with NaOH, slow fractional distillation thereafter should get you darn near 100% isopropanol. The production of absolute ethanol is comparable. They exceed the azeotrope concentration by drying with molecular sieves and then distill again.

grind - 28-9-2009 at 02:25

Drying of isopropanol azeotrope:
Add sufficient NaOH pellets (or powder) to get 2 clear phases. Separate the phases (you can use the NaOH solution for other purposes if the i-PrOH azeotrope was pure), repeat the NaOH treatment until the pellets remain unchanged.
Distill the remaining liquid together with NaOH pellets to get a nearly completely anhydrous isopropanol.
If you need an absolutely anhydrous product, add approx. 5 mass% of sodium metal to your min. 99% product, let the metal dissolve under reflux and distill. The recovery is approx. 70%.
No need for adding an isopropylester like in the case of ethanol, because the equilibrium

NaO-i-Pr + H2O = i-PrOH + NaOH

is nearly completely on the right side of the equation. That´s why i-PrOH as a secondary alcohol is a much weaker acid than ethanol. Or you can say sodium isopropylate is a much stronger base than sodium ethylate.

[Edited on 28-9-2009 by grind]

Arrhenius - 28-9-2009 at 07:04

I think we all know sodium metal is a great desiccant, and I also think few of us have it. Also, isopropoxide (pKa 16.5) and ethoxide (pKa 15.9) are almost the same in terms of basicity, though isopropoxide is a poorer nucleophile.

I think breaking the azeotrope with NaOH, then using magnesium metal (more reactive than aluminum) to get it anhydrous would be the way to go. OTC materials, lots of distillation, but no sodium to deal with.

entropy51 - 28-9-2009 at 14:19

I have used the same method posted by UnintentionalChaos and grind for drying iPrOH for making Al isopropoxide:

The 91% grade is shaken with 10% of its weight of commercial flake sodium hydroxide, separated from the aqueous layer which forms, then shaken with a little more sodium hydroxide, decanted and distilled.

You can test it for residual H2O with anhydrous CuSO4.

[Edited on 28-9-2009 by entropy51]

Picric-A - 28-9-2009 at 23:00

Do you dry the NaOH prior to use? Commercial NaOH nealry always contains as much as 10% water.
I suppose it would do no harm to the dessicant to keep it in an oven at 200degC for a while then use that?
Sure some carbonate will be formed but this can simple be filtered off?

UnintentionalChaos - 28-9-2009 at 23:54

Quote: Originally posted by Picric-A  
Do you dry the NaOH prior to use? Commercial NaOH nealry always contains as much as 10% water.
I suppose it would do no harm to the dessicant to keep it in an oven at 200degC for a while then use that?
Sure some carbonate will be formed but this can simple be filtered off?


Why bother? It's being used as a means to strip bulk water from the alcohol by mechanical seperation of phases. A few percent water in the sodium hydroxide should be irrelevant.

Final drying should be by molecular sieves, or some other powerful means of removing traces of water.

In my experience, NaOH is consistently quite pure and reasonably dry. Why dry in an oven, when you can readily fuse it to expel water. KOH is another story entirely and is often 85% or so, and cannot be dehydrated by fusion, except to red heat, IIRC.

Picric-A - 29-9-2009 at 01:45

Quote: Originally posted by UnintentionalChaos  
Quote: Originally posted by Picric-A  
Do you dry the NaOH prior to use? Commercial NaOH nealry always contains as much as 10% water.
I suppose it would do no harm to the dessicant to keep it in an oven at 200degC for a while then use that?
Sure some carbonate will be formed but this can simple be filtered off?


Why bother? It's being used as a means to strip bulk water from the alcohol by mechanical seperation of phases. A few percent water in the sodium hydroxide should be irrelevant.

Final drying should be by molecular sieves, or some other powerful means of removing traces of water.

In my experience, NaOH is consistently quite pure and reasonably dry. Why dry in an oven, when you can readily fuse it to expel water. KOH is another story entirely and is often 85% or so, and cannot be dehydrated by fusion, except to red heat, IIRC.


Sorry yes good point. I was confusing this with using NaOH to make anhydrous ethanol or sodium ethoxide from NaOH + EtOH

grind - 30-9-2009 at 04:31

@Arrhenius:
I didn´t know that sodium is so hard to get. Drying of solvents with sodium is so natural for me, so this idea didn´t come to me.
And of course, in this case you are right, OTC methods are better.
Houben/Weyl says drying of isopropanol with solid NaOH gives an anhydrous product which is miscible with pet ether and CS2 without a trace of cloudiness. I think such a product is satisfactory for the most "anhydrous purposes".

Another point:
With the isopropanol azeotrope at hand, you can also use K2CO3 (that should be OTC) to remove most of the water.

[Edited on 30-9-2009 by grind]

[Edited on 1-10-2009 by grind]

Sandmeyer - 30-9-2009 at 18:01

*I* thinks that a very simple and scalable method is a Swern-variation, if you like names, called Albright-Goldman oxadation. It uses acetic anhydride to activate DMSO, and it is conducted at room temperature (compare to Swern!). See their JOC papers from seventies... There are couple of them IIRC...

Edit by Nicodem: I seriously hope the momentarily regression into "swiming" was some kind of a bad joke!

[Edited on 2/10/2009 by Nicodem]

UnintentionalChaos - 30-9-2009 at 19:02

Quote: Originally posted by Sandmeyer  
SWIM thinks that a very simple and scalable method is a Swern-variation, if you like names, called Albright-Goldman oxadation. It uses acetic anhydride to activate DMSO, and it is conducted at room temperature (compare to Swern!). See their JOC papers from seventies... There are couple of them IIRC...


Swimming, are we?

Goddamnit, you should know better than that.

[Edited on 10-1-09 by UnintentionalChaos]

entropy51 - 2-10-2009 at 15:28

OTC Isopropanol for Al Isopropoxide

Since the subject of drying IPA for the isopropoxide prep has come up, I decided to try the prep using Iso-HEET, the IPA sold as a fuel line antifreeze. The regular HEET is methanol, take note. Iso-HEET gives no color with anhydrous CuSO4, whereas 91% IPA gives a blue color indicating the presence of water, no surprise.

I ran a small scale prep of Al isopropoxide using Iso-HEET and was pleasantly surprised to see that it went essentially the same as the prep does when using IPA dried on NaOH and distilled. The Iso-HEET was used directly from a fresh, unopened bottle without further treatment. The Al was turnings from my lathe, degreased with acetone and air dried.

I thought this might be of interest to those of you who can find Iso-HEET in your local hardware or auto supply store.

entropy51 - 2-10-2009 at 15:32

Quote: Originally posted by UnintentionalChaos  

Swimming, are we?

Goddamnit, you should know better than that.


SWIM, Swern, whatever.

If management is going to allow all manner of talk about illicit drug synthesis, the prohibition against SWIM is just plain silly.

Lighten up, otherwise the hypocrisy is palpable.

Actually the use of SWIM serves the useful purpose of identifying those with criminal intent so that the rest of us can choose to offer advice, or not, as the case may be.

[Edited on 3-10-2009 by entropy51]

Magpie - 2-10-2009 at 15:43

And what about swix and swij? I've seen those used recently too.

[Edited on 2-10-2009 by Magpie]

Sedit - 2-10-2009 at 16:08

Quote:
I thought this might be of interest to those of you who can find Iso-HEET in your local hardware or auto supply store.


That is good to hear and resonable considering it is made to aid in drying the fuel lines so excess water would be counter productive. It should be made mentioned though that a freind has recently lead me to believe that ISO-Heat has started putting an oil additive in there new formulation. They have told me that it can be seen from a yellow tint to the IpOH. Distillation is said to clear this right up though with no problem.

UnintentionalChaos - 2-10-2009 at 16:51

Quote: Originally posted by Sedit  
Quote:
I thought this might be of interest to those of you who can find Iso-HEET in your local hardware or auto supply store.


That is good to hear and resonable considering it is made to aid in drying the fuel lines so excess water would be counter productive. It should be made mentioned though that a freind has recently lead me to believe that ISO-Heat has started putting an oil additive in there new formulation. They have told me that it can be seen from a yellow tint to the IpOH. Distillation is said to clear this right up though with no problem.


My methanol and isopropanol are from heet and iso-heet respectfully. I did distill both before use, based on their claim of an anti-rusting agent and an old report on here of a high boiling residue upon distilling heet.

I dried both with an arbitrary amount of anhydrous MgSO4 and decantation before distilling, although they seemed to have negligible water content.

I didn't boil the flask completely down and opted to scrap the last 50ml or so of a 1L run, which probably contained mostly high boilers.

[Edited on 10-3-09 by UnintentionalChaos]

[Edited on 10-3-09 by UnintentionalChaos]

entropy51 - 3-10-2009 at 11:48

Why am I not surprised that the Department of Redundancy is drying and distilling pure, dry solvents?:D

I've used both flavors of HEET straight out of the bottle for many purposes, after a few preps where I compared them to reagent grade solvents. I think they are probably pure enough for most work. The isopropoxide prep is fairly demanding in terms of water content and it worked like a charm.

I just hope Sedit's news about "improved" formulations doesn't come to pass.

UnintentionalChaos - 3-10-2009 at 12:13

Quote: Originally posted by entropy51  
Why am I not surprised that the Department of Redundancy is drying and distilling pure, dry solvents?:D

I've used both flavors of HEET straight out of the bottle for many purposes, after a few preps where I compared them to reagent grade solvents. I think they are probably pure enough for most work. The isopropoxide prep is fairly demanding in terms of water content and it worked like a charm.

I just hope Sedit's news about "improved" formulations doesn't come to pass.


Do a quick bit of research before dismissing others' claims.

http://www.imperialinc.com/msds0055120.shtml
http://www.imperialinc.com/msds0055060.shtml

Both list 1% proprietary additive on top of 99% of the respective alcohol. The bottles do advertise a rust inhibitor, which is usually some sort of high boiling nonpolar substance.

See posts by Smuv and Mumbles: http://www.sciencemadness.org/talk/viewthread.php?tid=7990

entropy51 - 3-10-2009 at 12:30

Quote:
Do a quick bit of research before dismissing others' claims


I did more than a "quick bit" of research. If you read my post, you see that I compared HEET to ACS solvents in several preps and obtained the same results.

That is research, dude. I dunno why you think I hadn't looked at the MSDS. But 99% you're quibbling about?

I didn't dismiss anybody's claims. Just pointed out that what you were doing was, well, Redundant for anything except HPLC. I stand by that assessment.:P

Seems like you've gotten mighty persnickety about purity lately.
Quote: Originally posted by UnintentionalChaos  
Guess I'll join the fun. I don't have any reagent stuff and do lots and lots of my own purification....
Behind the mortar and pestle are three oxidizers. One was purchased at a health food store, one a hardware store, and one a farm supply place.
http://www.sciencemadness.org/whisper/viewthread.php?tid=161...

[Edited on 3-10-2009 by entropy51]

UnintentionalChaos - 3-10-2009 at 16:35

Quote: Originally posted by entropy51  

I did more than a "quick bit" of research. If you read my post, you see that I compared HEET to ACS solvents in several preps and obtained the same results.

That is research, dude. I dunno why you think I hadn't looked at the MSDS. But 99% you're quibbling about?

I didn't dismiss anybody's claims. Just pointed out that what you were doing was, well, Redundant for anything except HPLC. I stand by that assessment.:P

Seems like you've gotten mighty persnickety about purity lately.
Quote: Originally posted by UnintentionalChaos  
Guess I'll join the fun. I don't have any reagent stuff and do lots and lots of my own purification....
Behind the mortar and pestle are three oxidizers. One was purchased at a health food store, one a hardware store, and one a farm supply place.
http://www.sciencemadness.org/whisper/viewthread.php?tid=161...

[Edited on 3-10-2009 by entropy51]


Do you really have an issue with my desire to work with reagent-ish grade materials? I'd like to avoid any unexpected side reactions due to impurities. Other complications might be difficulties with crystallization or depression of the product's melting point. Characterizing and purifying the reaction products is often half the battle.

Sure, heet may work as-is for reactions, but that residue of rust preventative is going to bug me to no end and I'd kick myself if it caused problems later on. The drying was probably redundant, but I have pounds of MgSO4 so why not? My hardware store acetone was slightly wet when I got it, so why should I expect heet to be magically anhydrous?

In this case, the impurity is known, and a way to remove it that isn't completely unreasonable is known. Why not give my future reactions an ouce of prevention?

And if you're hinting at it; no, nobody ingests any of my reaction products. I'm just a bit (or very) anal.

At any rate, the three oxidizers are KNO3, NaNO3, and 35% H2O2.

The H2O2 is food grade and is now stored in a fridge. The NaNO3 and KNO3 are recrystallized fertilizer and stump remover respectively.

The bench is also much cleaner and more heavily stocked than it was at that time. Back then, I didn't even have a full distillation setup. I still don't have a fume hood, but it's on the short list.

Go find someone who's worth your time to harass.


[Edited on 10-4-09 by UnintentionalChaos]

aonomus - 16-11-2009 at 21:46

I know this thread is a bit old, but I stumbled across a paper that describes the preparation of aluminum isopropoxide without the mercury catalyst, instead using anhyd. AlCl3.

Richter, M. 2009. A New Catalyst for the Synthesis of Aluminum Isopropoxide. Chimicke Listy. 103 6:511-513

Unfortunately the paper is in Czech, and I can't seem to find another version of it. Also, link here http://www.chemicke-listy.cz/docs/full/2009_06_511-513.pdf

If this works, AlCl3 might boil off prior to the isopropoxide, making it difficult to completely rid the apparatus of other residues prior to the last fraction being distilled. Still, might be worth it if you don't have to handle mercury-anything.

Picric-A - 17-11-2009 at 02:42

why would you make something as simple as Al isopropoxide with something as hard to obtain (in sufficient quantities) as anhydrous AlCl3?

aonomus - 17-11-2009 at 06:11

I wasn't aware that anhyd. AlCl3 was hard to get, and I only remembered about this thread as I was browsing through journals.

DJF90 - 17-11-2009 at 07:19

Anhydrous AlCl3 poses a problem for some people. For others it is not such an issue. It is easily made from the elements, with careful drying of the chlorine gas and exclusion of moisture from the apparatus. Thanks for sharing the reference aonomus, despite it being in czech. Perhaps we have a member here who is able to translate for us. The key advantage to this preparation is the lack of mercury salts as a catalyst; many people would rather not work with them, myself included.

Picric-A: Aluminium isopropoxide is not "simple"... It is a versatile reagent in organic synthesis. Sometimes it may be difficult to appeciate its scope. Are you aware that it can effect the attached transformation? You might like to think how it does so, and more importantly, why...

Transformation.JPG - 15kB

[Edited on 17-11-2009 by DJF90]

Picric-A - 17-11-2009 at 08:01

Sorry i meant simple as in simple to make, dry isoproypl alcohol, add clean aluminium turnings (cleaned in HgCl2 (aq) ) then reflux till dissolved, distill off isopropyl alcohol then aluminium isopropoxide - simple!
As i said AlCl3 is also 'simple' to make via combination of the elements however more tricky in making usable amounts.

Sorry for any confusion.

DJF90 - 17-11-2009 at 09:52

While not as easy to make in bulk as the isopropoxide, the anhydrous chloride is still suitable for the preparative scale... 100g or so if you have the apparatus large enough for it (a combustion tube and a collection chamber with drying tube attached). If you make it on a "as needed" basis, then you can easily prepare the quantities you need (possibly even easier than the isopropoxide preparation).

Aluminium Isopropoxide Synthesis

Klute - 15-1-2010 at 05:28

As stated in the first page of this thread, I need Al(OiPr)3 for some Oppenhauer oxidations.. And Panreac is out of stock, so I won't be receiving my reagent until at least 3 weeks.. So I decided on preparing it myself.. Here is the report.


The procedure followed was that of Vogels 5th Ed., p 440, at 1/10th the scale.

All glassware used was oven dried 30min prior use.

IPA was dried by refluxing, then distilling over CaH2.



2,7g of aluminium foil was pressed as a small cigar then cut into small peices, then dried in the oven for a few minutes.

They were then placed in a 100mL 3-neck RBF, along with a stir bar, mounted with a addition funnel, a reflux condenser and a CaCl2 guard.



20mL of IPA were added to the flask via syringe.

50mg of HgCl2 were added to the addition funnel, followed by 10mL IPA. The salt was dissolved by heating with a hair dryer. The solution obtained was then added to the stirred aluminium, and the addition funnel removed. The flask was then immersed in a 100°C oil bath.




The solution soon started bubbling and turning grey. The flask was heated to reflux, the bubbling becoming stronger and stronger. The solution became completly turbid from the grey particules formed. The flask was refluxed until all the aluminium was dissolved ( 2H).



The flask was then left to cool overnight. The next morning, crystals had formed.



The flask was heated to dissolve the isopropylate, and transfered to a dried distillation setup.




A CaCl2 guard was placed between the aspirator and the setup.



The excess IPA was removed under weak vacuum until the mixture started getting very thick and foamming.



The residu had to be relocated in a larger flask to avoid excessive foamming, using dry IPA to rince the solids. Once all the IPA was removed, the thick sludge melted to a easily-stirred solution. The condenser was then removed, and a clean receiver attached directly to the adapter. Vaccum was increased, and heating continued.



At 158°C, a clear distillate started to be collected. Heating was diminished to afford a slow take off. The distillate was collected until only a solid residu was left in the still flask.





Thus 17,3g (84.7mmol) of aluminium isopropoxide was collected, giving a yield of 84,7%, not bad!

The yield is less than stated by Vogel surely because of the several relocations into a different flask, and the fact that a rather large still flask was used (there was alot of product refluxing when take off ceased).

The liquid did not solidify upon cooling.





JohnWW - 15-1-2010 at 06:51

Thanks for the full and graphic details, Klute. However, there is one apparent error in the accompanying text, viz. "IPA was dried by refluxing, then distilling over CaH2"; - isopropanol would react quite violently with CaH2 to form calcium isopropoxide and H2 (and Ca(OH)2 if any water is present), in a similar manner to the reaction with Ca metal. So you probably mean anhydrous CaCl2, or some other anhydrous Ca++ salt that readily takes up water (this could include CaO although its heat of hydration to Ca(OH)2 is quite high), used as a dessicant to remove H2O as an hydrous salt which preferentially dissolves in H2O rather than in isopropanol. Also, because of the approx. 70% constant-boiling-point azeotrope that H2O and isopropanol form, you could not have gotten past this composition if you started with commercial "rubbing alcohol" by simple distillation alone.

[Edited on 15-1-10 by JohnWW]

sonogashira - 15-1-2010 at 07:04

I'm not sure John; Armarego says:
"Most of the water can be removed from
this 91% isopropanol by refluxing with CaO (200g/L) for several hours, then distilling. The distillate can be
dried further with CaH2, magnesium ribbon, BaO, CaS04, calcium, anhydrous CuSO4 or Linde type 5A
molecular sieves." ;)

Klute, I think you have better equipment than I have seen in any university!

[Edited on 15-1-2010 by sonogashira]

mr.crow - 15-1-2010 at 07:21

Klute is back in the lab :)

Rubbing alcohol also comes in a 99% grade with a small amount of mineral oil added.

Could AlCl3 be formed in situ by bubbling chlorine into dry IPA and aluminum powder? Nah, the Cl2, HCl and a lewis acid would chlorinate everything :(

Perhaps the AlCl3 could be formed in ether or DCM first then IPA added after. AlBr3 might be easier to make by adding Br2. All this to replace 50mg of Hg.

Klute - 15-1-2010 at 07:24

Indeed, I used CaH2, not CaCl2, it hardly bubbles at first, surely the water, then stays as is, it doesn't react with the alcohol, the still was left 2 days and the hydride reacted vigorouslyw ith water..

aonomus - 18-1-2010 at 00:16

Any idea on what was left in the brown/black residue? Also (yes, wiki is not the best source, but its fast), why is the aluminum isopropoxide product a liquid that doesn't solidify?

Klute - 18-1-2010 at 02:39

The isopropoxide finally solidified to a gelatinous cristalline mass, it's just that it has tendency to supercool.. I prefer it liquid it's easier to handle!

And yup, Klute's back in the lab!! ;)

aonomus - 18-1-2010 at 04:53

Maybe its highly soluble in IPA, and not all of it was removed?

Klute - 18-1-2010 at 12:19

No, no, all the IPA was removed before the isopropoxide started refluxing in the distillation setup. The setup was dry when distillation started. And it's not that soluble in IPA as it cristallized out from the solution upon cooling..

benzylchloride1 - 24-1-2010 at 22:16

I recently conducted a large scale synthesis of aluminumn isopropoxide. A bottle of iso heet which is claimed to be 100% 2-propanol was poured into a 1L round bottomed flask. The liquid was brownish in color. 4A molecular sieves were then added and a solvent still was attached. The 2-propanol was refluxed for 3 hours and then distilled into another flask. The distilled alcohol was dried overnight over 4A molecular sieves.
27g of aluminum foil was cut into small pieces and place into a 1L round bottomed flask. 290 mL of the redistilled 2-propanol was added, along with 0.84g of mercuric iodide. The flask was swirled to disperse the mercury salt. A long Allihn condenser was attached, bearing a CaCl2 tube. The mixture was heated to reflux, causing the mixture to turn to a greyish color. The heat was removed and the mixture refluxed by itself. After the initial reaction had subsided, the heating was re-applied and the mixture was refluxed for 4 hours, the aluminum had all dissolved at this point. The heating was removed, and after standing over night, crystals of the crude product had formed. The mixture was then distilled at atmospheric pressure until all of the remaining 2-propanol had been removed. The vacuum adaptor was then directly attached to the distillation head and the isopropoxide was then distilled under reduced pressure using a Buchi portable water aspirator without a CaCl2 tube. The aluminum isopropoxide was collected between 160-180 degrees Celsius as a clear, viscous liquid. The product weighed 172 grams and the percentage yield based on the aluminum used was 84%.

[Edited on 25-1-2010 by benzylchloride1]

unome - 25-1-2010 at 00:13

Quote:
Quote: Originally posted by aonomus  
I know this thread is a bit old, but I stumbled across a paper that describes the preparation of aluminum isopropoxide without the mercury catalyst, instead using anhyd. AlCl3.

Richter, M. 2009. A New Catalyst for the Synthesis of Aluminum Isopropoxide. Chimicke Listy. 103 6:511-513

Unfortunately the paper is in Czech, and I can't seem to find another version of it. Also, link here http://www.chemicke-listy.cz/docs/full/2009_06_511-513.pdf


I was wondering if it would be possible, given that the Hg salts are only there to remove the oxide layer, thus allowing the alcohol to come into contact with the bare metal, if it would be technically possible to utilize a solution of NaOH/iPrOH (which would according the equilibrium be composed also of NaO-i-Pr and H2O), which would clean the oxide layer off the aluminium, and activate it.


UnintentionalChaos - 25-1-2010 at 10:45

Quote: Originally posted by unome  


I was wondering if it would be possible, given that the Hg salts are only there to remove the oxide layer, thus allowing the alcohol to come into contact with the bare metal, if it would be technically possible to utilize a solution of NaOH/iPrOH (which would according the equilibrium be composed also of NaO-i-Pr and H2O), which would clean the oxide layer off the aluminium, and activate it.



That would hinge entirely on whether sodium aluminate is soluble in isopropanol, which I suspect it isn't.

I strongly suspect that gallium salts would work here as a nontoxic alternative, however. A small amount of iodine might also work.

[Edited on 1-25-10 by UnintentionalChaos]

Picric-A - 25-1-2010 at 11:06

Quote: Originally posted by UnintentionalChaos  
Quote: Originally posted by unome  


I was wondering if it would be possible, given that the Hg salts are only there to remove the oxide layer, thus allowing the alcohol to come into contact with the bare metal, if it would be technically possible to utilize a solution of NaOH/iPrOH (which would according the equilibrium be composed also of NaO-i-Pr and H2O), which would clean the oxide layer off the aluminium, and activate it.



That would hinge entirely on whether sodium aluminate is soluble in isopropanol, which I suspect it isn't.

I strongly suspect that gallium salts would work here as a nontoxic alternative, however. A small amount of iodine might also work.

[Edited on 1-25-10 by UnintentionalChaos]


Adding a couple of I2 crystals works like a charm and the AlI3 product is easily seperated form the isopropoxide.

DJF90 - 25-1-2010 at 16:43

Are you speaking from personal experience or voicing a reference?

[Edited on 26-1-2010 by DJF90]

unome2 - 26-1-2010 at 15:44

Sorry to be using this acct (usually unome, but not on this laptop - finally got the sucker working again:P)

Here is a reference for using I2 or FeCl3 IIRC to make aluminium isopropoxide

[Cannot get it to upload, so 4shared will have to do:mad:]

[Edited on 26-1-2010 by no1uwant2no]

Isopropanol purification

Lambda-Eyde - 19-3-2010 at 10:02

Hey,

This might be a little off-topic but I feel it's relevant to aluminium isopropoxide synthesis.
I'm attempting to purify isopropanol. I started off with a blue-dyed cleaning solution, claimed to contain 60-100 % 2-propanol. I filtered it through activated charcoal and a cotton plug to remove the dye, that was a success. Now, I'm not sure about the water content, but I know it's not anhydrous.

I'm refluxing 250 mL of iPrOH over 30 g dry sodium carbonate right now. Potassium carbonate is normally recommended for drying of alcohols, but I don't have any. I take it that the sodium salt would do pretty much the same?

Setup: the boiling flask is a 500 mL Kimax round bottom boiling flask. A claisen adapter with a rubber thermometer adapter is attached. Also attached is a 300 mm Kimax Liebig condenser. On top of that is a 105° distillation adapter used as a drying tube, filled with calcium chloride. The heat source is a salt water bath heated with an induction stove.

Here are some pictures:










Now, the alcohol tested negative for peroxide with KI + starch, but I like to be better safe than sorry. Vogel recommends SnCl<sub>2</sub> for removing peroxide. I don't have any of it on hand, but I do have half a kilo FeSO<sub>4</sub>∙7H<sub>2</sub>O. I suppose it would be just as good as stannous chloride for removing any possible peroxides?

As of now, the alcohol has been refluxing vigorously for an hour. The thermometer is reading just below 81°C, indicating the 91 % iPrOH/water azeotrope. My plan is to reflux for another hour, filter, add ~5 grams of ferrous sulfate and sodium carbonate, then arrange for downwards distillation with protection from atmospheric moisture, discarding the last ~50 mL that doesn't come over.
Does that sound sensible?

[Edited on 19-3-2010 by Lambda-Eyde]

bbartlog - 19-3-2010 at 11:24

I'm pretty sure you will need to go to greater lengths to dry it before it is dry enough to make the isopropoxide. First of all, '60-100%' is such a big range that it would be nice to narrow it down some before even starting the project; you're talking about the difference between using a little drying agent and filling the flask full of it. As an alternative to analysis you could just distill over the azeotrope, which would give you a known amount of water to deal with, before drying and distilling again.

As for the drying agent, I would assume that different drying agents have different partition coefficients that would describe their effectiveness, with things like sodium metal way way up there and sodium carbonate not nearly so high. Practically speaking, I like to use quantities of drying agents such that they remain solid at the reflux temperature of my solvent, because I feel like the partition coefficient can't possibly be that high once the drying agent forms a hydrate melt (this may however be error and confusion on my part). I'm curious whether your Na2CO3 is still solid; the monohydrate does not melt until 100C, but that only amounts to 6g of water absorbed (!); while the Na2CO3 also forms a decahydrate this is a liquid hydrate melt at the reflux temperature of IPA, so I would expect it to form a separate liquid phase unless the IPA was quite dry to start with. I personally dislike both Na2SO4 and Na2CO3 because they need low temperatures to absorb a decent amount of water, and when those conditions are met they have a tendency to suddenly crystallize into a big hydrate mass that also traps a bunch of whatever it is you're trying to dry. Magnesium sulfate is a better choice for IPA in my opinion. But even so I suspect you will have to dry multiple times.

entropy51 - 19-3-2010 at 11:29

The stuff you bought was probably 91% already. There's no need to reflux it with anything, although refluxing with CaO would remove the remaining H2O; Na2CO3 will not. If you shake it up with K2CO3 or NaOH, a lower aqueous layer will settle out and can be drawn off. Dry Na2CO3 might work as well using an extraction like this. The peroxide (that you don't have) is only problematic if you distill it to near dryness. FeSO4 only removes peroxide in an acidified aqueous medium. SnCl2 is the only thing I know of that will remove peroxides while anhydrous.

There are threads here that describe a proper procedure, which this isn't. I think a paper describing the use of NaOH to get it anhydrous has been posted. See here

[Edited on 19-3-2010 by entropy51]

Lambda-Eyde - 19-3-2010 at 11:43

Thanks to both of you for answering.

bbartlog: I wasn't hoping to get absolute isopropanol from this procedure, just a more concentrated than the 91 % solution I (presumably) have.

I am ashamed at my selection of drying agents; I only have sodium carbonate, sodium hydroxide and calcium chloride! When I asked for epsom salts/bathing salts at the drug store, I was given some hippy crap tainted with dyes and perfumes...
Right now my economy is rather poor, but I will eventually buy K<sub>2</sub>CO<sub>3</sub>, CaO, KOH, P<sub>4</sub>O<sub>10</sub> among others.

Quote: Originally posted by entropy51  
The stuff you bought was probably 91% already. There's no need to reflux it with anything, although refluxing with CaO would remove the remaining H2O; Na2CO3 will not. If you shake it up with K2CO3 or NaOH, a lower aqueous layer will settle out and can be drawn off. Dry Na2CO3 might work as well using an extraction like this. The peroxide (that you don't have) is only problematic if you distill it to near dryness. FeSO4 only removes peroxide in an acidified aqueous medium. SnCl2 is the only thing I know of that will remove peroxides while anhydrous.

Thanks for the advice on reducing agents, I wasn't aware of that. I will have to get some tin and pure HCl.

Quote: Originally posted by entropy51  

There are threads here that describe a proper procedure, which this isn't. I think a paper describing the use of NaOH to get it anhydrous has been posted.

While doing this experiment I found exactly that paper in my chemistry folder. At least I got some valuable lab experience. :D

Next, I'll dry it with NaOH according to the method in the mentioned paper and distill.

By the way, is there any easy method for quantitatively analyzing the water content of the alcohol?

[Edited on 19-3-2010 by Lambda-Eyde]

entropy51 - 19-3-2010 at 12:13

Quote:
By the way, is there any easy method for quantitatively analyzing the water content of the alcohol?
Probably not. You can probably find a table of specific gravity vs. concentration, but it won't be that sensitive. If it doesn't turn anhydrous CuSO4 blue it's probably fairly dry. Even if you made it absolutely anhydrous it would absorb H2O from the air.

It probably need not be extremely dry to make isopropoxide. I use gas line anti-freeze straight out of the bottle with no problems. This is garage chemistry after all.


Reduce-Me - 21-4-2010 at 18:00

Why is the product distilled with vacuum?

maryam - 14-5-2010 at 10:34

what was the exact T and pressure used in the proceess. I cant get the alcohol distilled and i got only small amount of Al(iso)3 in solid state not liquid. I dont know Why the product doesnt sit in reciever flask.. vaccum must be so intense! any ideas?

benzylchloride1 - 14-5-2010 at 17:56

This may be slightly off topic, can titanium tetraisopropoxide be synthesized in a similar manner? The standard procedure is the reaction of titanium (IV) chloride with isopropanol. If this compound could be synthesized in this manner, this would open up many new synthetic options to the advanced amateur organic chemist. Titanium metal filings are fairly inexpensive, reaction with chlorine would not be very hard to conduct. Possibly, chlorine could be passed into a suspension of titanium powder in anhydrous 2-propanol, resulting in the formation of the desired titanium tetraisopropoxide.

Lambda-Eyde - 15-5-2010 at 03:06

Doesn't 2-propanol react with chlorine gas in the presence of a Lewis acid? Or does this only apply to HCl + 2-propanol?

DJF90 - 15-5-2010 at 03:24

Chlorine may oxidise the isopropanol. If you can make the titanium tetrachloride it should be fairly simple, just provide sufficient scrubbing to catch all that HCl given off when reacting the alcohol.

white rabbit - 25-5-2010 at 14:09

I have recently duplicated the synthesis as described by Klute. I used 91% IPA. It was combined and shaken with NaOH (10% by weight) and left to settle out the aqueous layer and then distilled. It was then refluxed and distilled over Na and under nitrogen.

I then used the dry IPA (400 ml) with 1.65g HgCl2, .2g Iodine and 30g aluminum foil to synthesize the Al(O-i-Pr)3. This was done by first removing the air from the reaction flask and condenser with N2. The pot temp, when refluxing began, was 77*C. I refluxed for about 2 1/2 hours to dissolve all of the Al. After sitting over night, the IPA was removed by distilling. The still head temp was 78*C. As soon as the still head temp started to decrease and pot temp began to increase, I removed the condenser and placed the 105* vacuum adapter and a fresh receiver directly to the still head. Vacuum was then started and gradually increased to 10mm. At 185*C the product was vigorously refluxing on the top portion of the 1liter flask but not coming over. At this point I completely insulated the top of the flask and the product began to come over in a hurry. Approx 250ml had collected when it abruptly stopped. I removed the insulation and saw that there was only a dark gray semi solid mass left.

The product was a clear, somewhat refractive, thick liquid, which after 2 days, solidified.

white rabbit - 26-5-2010 at 14:42

Here are a few pics of the process
removal of excess water by NaOH
2Propanol 1s.JPG - 31kB


Distilling over sodium
Absolute 2Propanol  2.JPG - 45kB

Isopropoxide reaction complete
Al Isoprpoxide 5s.JPG - 57kB




driving off the excess IPA
Aluminum Isopropoxide 6s.JPG - 33kB

distilling over the isopropoxide
Aluminum Isopropoxide 9s.JPG - 34kB

Aluminum Isopropoxide 7s.JPG - 36kB

final product
Aluminum Isopropoxide 4.JPG - 23kB

maryam - 4-6-2010 at 13:27

Did you use high vaccum(pump)?(less than 5mm Hg)

maryam - 4-6-2010 at 13:49

Also Is it enough to use just molecular sieve to dehydrate the alcohol?

white rabbit - 4-6-2010 at 13:54

The vacuum pump I used only got down to 10mm and molecular sieves with work just fine if you use enough of them.

DJF90 - 4-6-2010 at 16:10

You shouldn't be pulling a vacuum on flat bottom flasks.

white rabbit - 4-6-2010 at 18:33

True! But I like the way they sit on the counter when I'm done and that one is really thick.

maryam - 7-6-2010 at 09:30

my Aluminum starting material is Al metal(Granular) in place of aluminum foil..Is adding iodine important in this case?

maryam - 7-6-2010 at 09:34

In first step of solid liquid reaction did you take out released H2 gas(purge N2, Use ballon) ? How log the disstilation took? Actually I am inorganic chemist that s why i have hard time in making it!!thanks for the help..

white rabbit - 7-6-2010 at 14:11

I just left the N2 flowing about two bubbles per second and a CaCl2 guard at the top of the condenser. The first step took about 4 hours including all the reflux time. I added the Iodine dissolved in a solution of IPA after the reflux had started. After the addition I noticed an increase in reaction rate. The second step, under vacuum, only took about 40 minutes.

The granular aluminum will work ,however, the reaction rate may be quite a bit slower because of the lower surface area, (I'm assuming that the shredded aluminum foil has more). You need to have enough Hg to properly amalgam the aluminum.

un0me2 - 14-8-2010 at 14:05

Quote: Originally posted by UnintentionalChaos  
Quote: Originally posted by unome  


I was wondering if it would be possible, given that the Hg salts are only there to remove the oxide layer, thus allowing the alcohol to come into contact with the bare metal, if it would be technically possible to utilize a solution of NaOH/iPrOH (which would according the equilibrium be composed also of NaO-i-Pr and H2O), which would clean the oxide layer off the aluminium, and activate it.



That would hinge entirely on whether sodium aluminate is soluble in isopropanol, which I suspect it isn't.

I strongly suspect that gallium salts would work here as a nontoxic alternative, however. A small amount of iodine might also work.

[Edited on 1-25-10 by UnintentionalChaos]


The insolubility of the aluminate in the isopropanol is the reason I suggested it. It could be removed by filtration, or left behind by distillation. The reaction with the aluminium would remove the oxide, the clean aluminium would react with the alcohol. There is a similar procedure starting from aluminium with HCl to give aluminium dithionite in this patent which of course could also be tried (1-2M HCl gas dissolved in anhydrous i-PrOH) would also clean the oxide layer off the aluminium - forming AlCl3 in situ, or at least a catalytic amount thereof.

Don't know why, but that appeals to me - whether that would be enough to initiate the reaction I could not say for certain.

Random - 4-11-2010 at 12:46

Could I put small amount of copper chloride to the al-isopropanol mixture to "activate" the al without hg salts? CuCl2 dissolves the aluminium alone.

digitalemu - 5-11-2010 at 17:21

Just watch it with your own eyes being performed with some background music :) Nice work ytmachx... Have some great vids.

http://www.youtube.com/watch?v=axxbIWOge_o


maryam - 12-4-2011 at 15:52

Anyone knows how to measure purity of aluminum isopropoxide?

aluminum isopropoxide prep problem

Cloner - 6-8-2011 at 13:38

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.

Can atmospheric water be the problem? I have no idea how sensitive this reaction is to water and in what manner water disturbs it. The IPA is dry to begin with (sodium was dissolved in it, then it was distilled).

[Edited on 6-8-2011 by Cloner]

Nicodem - 6-8-2011 at 14:26

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.

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.

Cloner - 6-8-2011 at 15:52

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.

hosko - 23-10-2011 at 02:02

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]

Paddywhacker - 12-1-2012 at 17:29

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

Aluminum Isopropoxide issues

Alkoxide - 13-5-2015 at 12:30

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?

byko3y - 13-5-2015 at 14:17

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.

Alkoxide - 13-5-2015 at 14:33

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.

byko3y - 13-5-2015 at 14:48

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.

Alkoxide - 13-5-2015 at 14:55

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.

byko3y - 13-5-2015 at 15:03

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.

Alkoxide - 13-5-2015 at 15:12

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?

byko3y - 13-5-2015 at 16:04

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.

Alkoxide - 13-5-2015 at 20:47

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).

byko3y - 14-5-2015 at 09:36

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.

Pumukli - 14-5-2015 at 11:53

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]

Aluminum isopropoxide prepared by various methods

WGTR - 16-5-2015 at 10:17

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 683 times

byko3y - 17-5-2015 at 16:11

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.

blogfast25 - 17-5-2015 at 17:07

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

byko3y - 17-5-2015 at 17:16

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.

blogfast25 - 17-5-2015 at 17:50

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]

WGTR - 17-5-2015 at 18:47

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

Pumukli - 17-5-2015 at 20:52

"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.

blogfast25 - 18-5-2015 at 06:03

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! :o

[Edited on 18-5-2015 by blogfast25]

Pumukli - 18-5-2015 at 11:15

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. :-)

blogfast25 - 18-5-2015 at 11:37

Quote: Originally posted by Pumukli  
Actually a dark solution is expected.


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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