Sciencemadness Discussion Board

Simple(er)Aluminum Isopropoxide prep experiment for later this week.

scientician - 19-12-2010 at 17:51

I am seeking comments on a a simple experiment I have underway to see if Aluminum isopropoxide can be prepared quickly and under relatively mild conditions. I intend to react anhydrous Aluminium III Chloride and sodium O-Pr in stoichiometric ratios to yield NaCl and Al OiPr. The aluminum isopropoxide would then be distilled off for the work up.

3 Na i-O-Pr + AlCl3 --------> Al i-O-Pr + 3NaCl

Additionally, the sodium isopropoxide will be prepared using absolute isopropanol and sodium hydroxide. This may require heating under reflux, as the solubility of NaOH in IPrOH is fairly low (about 80g/L.) Of course, drying will be necessary.

The Na OiPr will be added dropwise to the AlCl3, which will be dissolved in more isopropanol.

Any thoughts or comments? Does anyone know better, or have suggestions for how it could be improved? Has this already been attempted by anyone wiser than me?

UnintentionalChaos - 19-12-2010 at 18:34

Do a search on this site. There is an extremely easy prep of Al(OiPr)3 that doesn't require aluminum chloride or sodium isopropoxide.

bbartlog - 19-12-2010 at 18:35

Thermodynamically, it looks nice (to the point of being rather exothermic I imagine). I can think of a few side reactions that seem plausible, though, depending on temperature:
- dehydration of isopropyl alcohol to propylene
- chlorination of isopropyl alcohol
- ... possibly followed by reaction of the 2-chloropropane with your sodium alkoxide

Basically AlCl3 may be strong enough to do ... things... to your proposed solvent. Even if my speculation on the specifics is off, AlCl3 in IPA is a mix of species and may not give you one neat primary reaction.
Still would be interesting to try. I advise keeping it cold.

scientician - 19-12-2010 at 22:31

Interesting. Since both the reagents are solids at STP, it could feasibly be reacted solvent free. However, were such a reaction to go horribly, horribly wrong, the very best to could hope for would be tattooed-on eyebrows and a furious fire Marshall. Solvents could well add lingering flame to the hypothetical instantaneous decomposition.

The inadvertent production of peroxides which - er - rapidly decompose into a gaseous state is also quite possible. Reactions which produce that kind of compound are usually conducted at colder temperatures, especially with peroxides.

So the products could be PriO-OiPr(?) + Al(s) + NaCl(s) Yeah, no thanks.

Fortunately, the referenced thread on AlOiPr has a link to an article on the use of aluminum III chloride as a catalyst for starting the reaction. There's enough discernible info on the tables to find a good starting point experimentally, despite the language barrier.

Thanks for helping me think this through a little more.

sonogashira - 21-12-2010 at 12:10

Quote: Originally posted by scientician  
I am seeking comments on a a simple experiment I have underway to see if Aluminum isopropoxide can be prepared quickly and under relatively mild conditions. I intend to react anhydrous Aluminium III Chloride and sodium O-Pr in stoichiometric ratios to yield NaCl and Al OiPr. The aluminum isopropoxide would then be distilled off for the work up.

3 Na i-O-Pr + AlCl3 --------> Al i-O-Pr + 3NaCl

Additionally, the sodium isopropoxide will be prepared using absolute isopropanol and sodium hydroxide. This may require heating under reflux, as the solubility of NaOH in IPrOH is fairly low (about 80g/L.) Of course, drying will be necessary.

The Na OiPr will be added dropwise to the AlCl3, which will be dissolved in more isopropanol.

Any thoughts or comments? Does anyone know better, or have suggestions for how it could be improved? Has this already been attempted by anyone wiser than me?


In my experience, dissolving NaOH in (room temperature and "warm") IPA is extremely difficult/impossible. KOH has a much better solubility, so I would suggest trying that if you have problems; although I never tried it at reflux.

If I recall, amalgamated aluminium in IPA is the normal preparation. Maybe you can try with using gallium to activate the aluminium (instead of mercury).

I only learned of reducing gallium/aluminium mixtures recently, but this seems promising for the wise mercury-fearing chemist!

Best of luck! :)

not_important - 21-12-2010 at 16:29

The water released by the ROH + NaOH <=> RONa + H2O will react with the AlCl3. A better way to use AlCl3 is to use the anhydrous alcohol plus AlCl3, and add a tertiary amine to sop up the HCl released.

hosko - 23-10-2011 at 01:50

Hello everyone....

I would like to ask something about water or vapor trap... I want to obtain Aluminum Isopropoxide by vacuum distillation... Then, I have made solid-liquid reaction and remove the excess isoprophyl....Now I need to distill pure AIP (final product)... In this stage I don't use any condenser, it means I have used short path distillation... Problem is like that my distillate in a gaseous state but it must will become in liquid form... I have used 10mmHg pressure but never used any trap... Trap, it could be effect distillate form (liquid or gaseous)?

scientician - 29-5-2012 at 01:06

Following up on this old post - a very small amount of gallistan (gallium tin alloy) worked brilliantly for synthesizing aluminum isopropoxide. I chose gallistan only because it was readily available to me at retail in the form of faux mercury thermometers at the Rite-aid, and I figured if it "sort of" worked then investing in pure gallium would be worth my while.

After cutting the aluminum foil into small squares, I took the extra step of tossing them in a cheap blender. This wrinkled them up into tiny little balls, making them easier to transfer into my flask and allowing the gallistan to settle on them (it tends to sink to the bottom very quickly where it promptly does nothing.)

After combining the reagents I shook the hell out of my flask to help the gallistan settle on the aluminum. I heated it to about 75C and the reaction really took off. So much so that I had to take it off the burner for about 90 minutes while it refluxed by itself. As soon as it started to settle I returned it to 75C, where it happily bubbled for 12 hours. (The bubbles were hydrogen gas evolving, no need to hold it at reflux.) Once the reaction completed I removed it from the burner and stoppered it to let it cool.

There is a good amount of grey shit in there, and some excess iPrOH. There is also a great deal of crystalline aluminum isopropoxide (I assume) clinging to the side of the glass. I am too big a chicken to pull a vacuum on it and distill it. I did not expect this to work so well, and accordingly I used a very basic setup involving a cheap erlenmeyer flask and a rubber stopper with a tiny hole in it - nothing like the elegant glassware seen elsewhere in these forums (I do have it, just didn't want to set it up for what I assumed would be a disappointing outcome at best.)

So, there's probably no need to rely on mercury or iodine for this. I'll re-attempt this with a more definitive setup later next week and hopefully I'll be able to purify and confirm. But as of right now, using gallistan instead of mercuric chloride looks very promising.

Alkoxide - 1-4-2016 at 04:31

I was able to repeat scientician's synthesis using gallium as a catalyst.

Procedure:

250mL of 91% isopropanol, 19.7g of NaOH, and a stir bar was added to a 500mL RBF and stirred for 25 minutes. The magnetic stirrer was turned off and the liquid in the flask separated into two phases. Nearly all the NaOH dissolved. The lower aqueous phase was removed in a 250mL sep funnel and emptied into a 100mL beaker. The aqueous phase was 20mL, including dissolved NaOH, which did not account for all the water in the isopropanol. An arbitrary amount of NaOH was added to the previous RBF along with the organic layer from the sep funnel and stirred for 20 minutes. After stirring, there was no noticeable aqueous phase so the NaOH must have soaked up any remaining water. Most of the NaOH remained undissolved. The liquid was added to a clean sep funnel (checking there was no aqueous phase) and then drained into a clean 500mL RBF. A simple distillation apparatus was assembled with a drying tube protecting the vacuum takeoff adapter. The isopropanol was distilled until a large block of NaOH had precipitated in the flask. During the distillation, the still head temperature was 76 degrees and the boiling point of the isopropanol in the flask was 82 degrees (Lit. value for absolute isopropanol 82-83, Vogels). Roughly 100-200mL of absolute isopropanol was collected.

13.5 grams of aluminum foil cut into small squares, several small pieces of gallium (probably between 0.5-1g), and a clean stirbar were added to the 500mL flask with the dry isopropanol. A 600mm leibig condenser with a drying tube was mounted on top of the flask for refluxing. Plastic tubing was connected to the outlet of the drying tube and run out a window to vent hydrogen gas away from the lab area and any ignition sources. The isopropanol was refluxed for about an hour and a half without any change in the aluminum foil or isopropanol color. At this point, refluxing was stopped and the flask was allowed to cool. I drilled a few holes in a block of 6061 aluminum and added a few grams of fresh turnings to the flask (thinking maybe there was a polymer coating on the foil that was keeping it from reacting). Refluxing was continued and after an hour the color of the isopropanol began to darken and the aluminum in the flask was visibly corroded. For the last hour of refluxing, heating was discontinued and the mixture refluxed under its own energy and the magnetic stirrer was turned on. After approximately 5 hours and 15 minutes of refluxing in total, the mixture in the flask stopped boiling and cooled. The flask was setup for simple distillation with a drying tube protecting the vacuum take off adapter. Several drops of isopropanol were collected (perhaps <2mL) and there was still finely divided bits of aluminum in the flask so aluminum was likely to be in excess. Approximately 90mL of a thick, maple syrup consistency, black liquid was decanted and poured into a 500mL media bottle for storage. I probably will not vacuum distill this, since when used in an oppenauer oxidation aluminum metal will precipitate anyway so the metal mixed with the product here does not bother me.

[Edited on 1-4-2016 by Alkoxide]

CuReUS - 1-4-2016 at 05:07

not related to this thread but IMHO,there are many other OTC reducing and oxidising agents that are easier to work with than Al-isopropoxide.
if you want to reduce you can use dithionite,for oxidation acidic bleach can be used.

DrMethyl - 7-4-2016 at 10:10

Here is an easy way to make aluminium isopropoxide. The synth comes from 420chan board.

Workup of Aluminium Isopropoxide
In 250two neck RBF, set one neck up for reflux and one neck up for desiccation. Prepare a drying tube with CaCl2 and link it up to the vacuum adapter in the desiccation neck. Heat all the glassware to an ambient temperature of 80deg C upwards towards the allihn condenser. Proceed to blow air through the drying tube into the flask. Seal off the allihn condenser with a small amount of aluminium foil.
Desiccated aluminium dust (27.98g, 1.00mol) is ground to remove oxide layer and HgCl2 (0.01g) was added. The metal semi-amalgam is added to the bottom of the flask and desiccated isopropanol (250ml, 3.30mol) is injected carefully into the vacuum adapter septum. The vessel is left to reflux for 4 hours.
While still on reflux, the allihn condenser is removed and a 3-way adapter with a thermometer adapter is quickly added. The vacuum is attached to the receiver joint of the 3-way with a one neck 250 RBF while stoppering the side arm of the two neck flask tightly. A distillation is run until only solid aluminium dust remains in the still flask.
A yield of 80% of 1mol aluminium isopropoxide (163.4g) should be achieved.

Uxleumas - 10-1-2024 at 18:42

a bit of indium (~0.1g In/2g Ga) to the gallium seemed to make the reaction go quicker in my experience.
Could also just be that I wasn't heating the mixture for long enough before.

Organikum - 15-1-2024 at 12:23

Will Gallium or Mercury amalgamate Titanium? Would this open the way for Titanium(IV)isopropoxide by the method as here described for Aluminium Isopropoxide?

thx.

bnull - 15-1-2024 at 13:44

Apparently yes. There is a 1993 paper by Y. Ohnishi and Y. Wakahata on how to make titanium-mercury alloys (it is in Japanese, though), for example.

I'm not sure if the Ti(IV) isopropoxide would be the only product. You could end up with a mixture of isopropoxides, or an ether, or both. Aluminum has only one (immediately useful) valency, that's basically why the procedure works. If you oxidize the titanium to +4, maybe by electrolyzing a non-aqueous solution of isopropanol with the amalgam as the anode, it could work. As long as the cathode is separated from the products (by a salt bridge or semipermeable membrane, or even glass wool wrapped on it), you should get a decent yield.



[Edited on 16-1-2024 by bnull]