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Author: Subject: proposed reduction via Al/Ga
postart
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[*] posted on 19-7-2010 at 12:25
proposed reduction via Al/Ga


I came up with an idea for reduction using gallium rather than HgCl. What does anyone think about it, sound viable?

Reductive amination of ketone via Gallium/Al + amine:
To the aluminum amalgam there was added 295g methylamine hydrochloride dissolved in 300ml hot water, 750 ml isopropanol,
700ml 25% aqueous NaOH,197.5g ketone and finally 1750ml isopropanol. Hydrogen was vigorously evolved from the
aluminum amalgam, and the temperature of the solution rose quickly. The reaction rate was controlled by immersing the reaction flask in cold water during 2h, whereafter it was allowed to stand at room temperature with magnetic stirring
overnight, with attention being given to the reaction mixture during the first hour so that the temperature did not rise
over 50°C.

Aluminum gallium amalgam prep:
The gallium amalgam is an excellent substitute in an al/hg reductive amination procedure. it's non-toxic, and stronger.
A search of the internet will reveal, a patent where it has been used already to reduce NO2 and NH2. gallium is also
easily sourced. If you wanted to make a Ga-Al alloy, simply gently heat the Ga (m. pt. 29.7646ºC) until it is liquid, and
it will start to readily form an alloy by dissolving the Al. However, the resulting amalgam will have a higher melting
point than the liquid Ga, so you would have to keep heating the mixture until all the Al is dissolved. In a 10,000ml
wide-mouthed flask, 190 grams of aluminum foil cut to 3x3cm pieces was amalgamated with 5grams gallium in 7000ml
warm water until the solution became greyish, and hydrogen bubbles was evolved in a steady rate from the aluminum surface. The water was decanted off, and the aluminum amalgam was washed with 2x5000ml cold water.
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Melgar
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[*] posted on 19-7-2010 at 13:11


Hmm, I wonder what ketone you might be using? ;)

I've used aluminum/gallium for other reductions, (not reductive aminations, I'm not THAT kind of chemist!) and generally did this by melting the two together and using this lump of metal to do the reduction. Also, alloying the gallium with indium and tin will lower its melting point to well below room temperature. This makes it pool in the bottom of the flask, where it can be collected and reused later.

Not all aluminum is the same, also. Aluminum foil is relatively pure aluminum, but most aluminum is some sort of alloy that doesn't work well for this reaction. Other sources of pure aluminum include aluminum coins from countries where they have them. (Chilean 1-peso coins work remarkably well) Also, aluminum muffin tins are fairly pure aluminum.
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[*] posted on 19-7-2010 at 19:01


Hmm, I would be surprised if coin aluminum is all that pure.

Very pure aluminum is very weak stuff. It's like a stiff, shiny clay.

The best source is aluminum wiring. Strip off the insulation, melt it if you have the equipment, or just use it as is.

I melted a bunch of wire into a one inch diameter bar a few feet long. It's soft enough to bend by hand.

Ordinary alloys, like wrought and extruded products, are not all that impure, the major additions being magnesium, silicon or copper, less than 10% total. Cast products are less pure, having a substantial amount of silicon (usually 10-14%, special alloys up to 24%), plus a small amount of other metals.

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[*] posted on 20-7-2010 at 13:51


I had same idea ever since I sabotaged pressurized aluminum cans with chunk of Ga...

If you don't use pure Hg but Hg salts for that task,why don't you use Ga salt!?
It would definitelly simplify your whole procedure!
I don't have anyting but to reduce right now to test this,so please inform us if you suceed...

And as long as I know,ordinary aluminum foil has no more than 2% of other crap in it,
how abbout disposable pie pans!?
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[*] posted on 20-7-2010 at 14:48


This is good idea postart. I raided Wiki for a short quote, and I came up with some pertinent information. They suggest that the alloy Galinstan (Gallium/Indium/Tin) might do the trick nicely.


"Energy storage"

"Aluminium is reactive enough to reduce water to hydrogen, being oxidized to aluminium oxide. However, the aluminium oxide forms a protective coat which prevents further reaction. Galinstan has been applied to activate aluminum (removing the oxide coat), so that aluminum can react with water, generating hydrogen and steam in a reaction being considered as a helpful step in a hydrogen economy.[26] A number of other gallium-alluminum alloys are also usable for the purpose of essentially acting as chemical energy store to generate hydrogen from water, on-site." WIKI

Whereas, others are looking at this dissolving metal reaction as a means of energy storage. It is the basic dissolving metal reaction that chemists often use for organic reductions.

Gallium seems available and pretty non-toxic. I'll do a check on Galinstan.

OK....Check I did. Galinstan is being used in Mercury-Free thermometers. This figures to be the right thing, right here.

http://cgi.ebay.com/MERCURY-FREE-ORAL-THERMOMETER-/190420317...

A little spendy for a small amount. But, soon they will be available at garage sales, at a large discount.

[Edited on 20-7-2010 by zed]
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[*] posted on 20-7-2010 at 19:08


You can get these thermometers at drugstores and probably department stores for $7-$8. The galinstan can be reused after collecting it where it pools in the bottom of the containers. It can be cleaned with dilute HCl, but strong HCl will slowly dissolve it. Also, galinstan will wet glass and just about everything else too, but dilute acids and bases will make it ball up and pool together.
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[*] posted on 23-7-2010 at 12:55


How much galinstan do the thermometers have in them. Also I was thinking of prepairing an Al/Ga amalgam without water?
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[*] posted on 24-7-2010 at 10:21


I don't have a thermometer on hand. Find out the alloy's density/weight per ML.....Guesstimate the volume of alloy in the thermometer bulb, in ML...Multiply one by the other...And Shazzam. You get an estimate of the Wt of the alloy present.

If Gallium Chloride reacts in the manner that Mercuric Chloride does, it might be advantageous to use the Chloride. By treating Aluminum Foil with a mercuric salt in solution, a very fine film of amalgam is produced on the foil's surface. A little mercury goes a long way.

Since, the foil usually has a large surface area, actually physically wetting(or painting) the surface of the foil with a small amount of metallic Gallium or Galinstan, might present problems. Lotta wall space...Pretty thick paint.

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[*] posted on 25-7-2010 at 14:06


Quote: Originally posted by zed  

Since, the foil usually has a large surface area, actually physically wetting(or painting) the surface of the foil with a small amount of metallic Gallium or Galinstan, might present problems. Lotta wall space...Pretty thick paint.



Right, silly me the water should definitly be present to paint the large surface area of the Al.
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[*] posted on 25-7-2010 at 14:54


I think your misunderstanding what hes saying, by wetting hes not saying with H2O hes talking about wetting with the Gallium itself. Instead it might be idea to dissolve the salt of the gallium in a solvent and use that instead since you would get away with using much less Gallium in the process.




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[*] posted on 25-7-2010 at 17:13


Thats what I meant. I was thinking H2O would be the solvent. Is elemental Ga soluable in H20?
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[*] posted on 25-7-2010 at 21:01


I think it's a pretty good bet that Gallium isn't soluble in water. However, the guys are suggesting that it may dissolve in strong HCl.

Metals being metals, and HCl being HCl....Ga dissolving in concentrated HCl, suggests that Gallium Chloride is being formed. Gallium Chloride in solution, like Mercuric Chloride in solution, will probably react with metallic Aluminum....The result should be that the Chloride ion combines with a small amount of Aluminum to form a small amount of AlCl3 type material....And in the process, Metallic Gallium is plated out, onto the now activated Aluminum. Bingo.....Ga/Al amalgam.

[Edited on 26-7-2010 by zed]
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[*] posted on 26-7-2010 at 06:58


For some reason gallium chloride never seemed to work very well. It may be because gallium is solid at room temperature, or because galinstan is composed of three different metals that all plate out differently. But it never worked as well as the mercury chlorides. After a lot of experimentation, the best method I found was melting the two metals together before adding them to the solution.
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[*] posted on 26-7-2010 at 17:05


I was thinking the same. Make a Gallium-aluminum alloy; when added to a solution containing H2O hydrogen will be generated. Any thaughts on temp and measurments? More Ga may be called for but it still beats Hg salts if you ask me.
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[*] posted on 26-7-2010 at 17:21


Theory is good, theory is helpful, but nothing trumps experience.

So, Melgar......Stirring? Does this lump of metal have a large enough surface area to react vigorously?

postart....Do you have the number of that patent you mentioned?
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[*] posted on 27-7-2010 at 10:10


Well, the aluminum-gallium mixture reacts more vigorously than a mercury-aluminum one. Thus, you're better off using less surface area, and perhaps alcohol as a solvent instead of or in addition to water. I never performed any quantitative measurements, but a few drops of gallium on a chilean 1-peso coin would eventually react so vigorously with water that it would look like it was boiling. I'm not sure if the lower surface area has a major effect on yields, but it wouldn't seem like it, since the vigorous bubbling of the reaction would seem like it'd mix the solution sufficiently.
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[*] posted on 16-8-2019 at 03:23


Quote: Originally posted by Melgar  
For some reason gallium chloride never seemed to work very well. It may be because gallium is solid at room temperature, or because galinstan is composed of three different metals that all plate out differently. But it never worked as well as the mercury chlorides. After a lot of experimentation, the best method I found was melting the two metals together before adding them to the solution.


what solution exactly? what quantities? why does it have to be a gallium salt, can not you just do an amalgam using gallium and aluminum and use a piece of it for generate hydrogen like crazy in the p2np solution??

[Edited on 16-8-2019 by skull]
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