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blogfast25
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And do report back here, presto! We need all the help we can get...
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Bhaskar
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http://www.instructables.com/id/Make-Potassium-Metal/ here is the synthesis for the video.
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Bhaskar
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Here is the video for the synthesis-
http://www.instructables.com/id/Make-Potassium-Metal/
Shit, sorry for the extra post, and there isn't an edit option for it!
[Edited on 06-10-2011 by Bhaskar]
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White Yeti
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there is, the top right hand corner, hit edit, and !delete this message! to get rid of the second post.
"Ja, Kalzium, das ist alles!" -Otto Loewi
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hames
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hi,I got hold of about 150mls of t-butanol but its azeotropic is there anyway of purifying and drying it without using sodium wire.can I freeze it to
separate it out or can I use it in the potassium synthesis as is.
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ScienceSquirrel
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Thread Pruned
13-3-2012 at 05:16 |
garage chemist
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I would dry it with potassium carbonate: add plenty of it and magnetically stir for a few hours, decant the liquid, separate the heavy aqueous K2CO3
solution in a separatory funnel if necessary, add some fresh K2CO3 and stir again, if the K2CO3 doesn't clump then you're done. If not, dry agin with
fresh K2CO3.
A little residual water in the tert-butanol shouldn't hurt since the KOH contains 15% water anyway. K2CO3 doesn't remove all of the water, keep that
in mind.
Anhydrous t-BuOH can be prepared from the predried product by dissolving sodium into it (doesn't have to be wire) and distilling.
[Edited on 13-3-2012 by garage chemist]
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blogfast25
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Quote: Originally posted by hames  | | hi,I got hold of about 150mls of t-butanol but its azeotropic is there anyway of purifying and drying it without using sodium wire.can I freeze it to
separate it out or can I use it in the potassium synthesis as is. |
What's the azeotropic water content? If it's not too high I'd use the product as such. The first part of the reaction is about reacting away most of
the water anyway and the amount of additional water from your t-butanol shouldn't bother too much. At worst yield of K might be a little lower...
garage chemist:
Any progress on synthing longer chain 2-methyl t-alcohols?
[Edited on 13-3-2012 by blogfast25]
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AndersHoveland
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Although this method has worked to make elemental potassium, it may likely not work for making lithium.
Lithium ions are more acidic, so would tend to form somewhat more covalent bonds with hydroxide ions. Lithium ions are also much smaller than the
bulkier potassium ions, so the crystal lattice energy with hydroxide ions may be much greater. In other words, the formation of LiOH is significantly
more favorable than KOH.
That is what is so interesting about this reaction. Potassium is usually a much more reactive element than lithium, and more difficult to make. But
this reaction takes advantage of the unique reactivity differences of potassium.
But you could always use the potassium you have made to reduce lithium chloride to metallic lithium.
LiCl + K --> KCl + Li
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blogfast25
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| Quote: Originally posted by AndersHoveland |
Although this method has worked to make elemental potassium, it may likely not work for making lithium.
Lithium ions are more acidic, so would tend to form somewhat more covalent bonds with hydroxide ions. Lithium ions are also much smaller than the
bulkier potassium ions, so the crystal lattice energy with hydroxide ions may be much greater. In other words, the formation of LiOH is significantly
more favorable than KOH.
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Firstly, AFAIK no one has attempted reduction of LiOH by Mg, catalysed by t-alcohols, so we don't really know. LiOH is of course quite a bit harder to
get than NaOH or KOH, at least for the hobbyist.
I doubt if lattice energy will play a huge part here: the STP HoF for LiOH is - 485 kJ/mol, for KOH it's - 425 kJ/mol (both values NIST webbook). That
means that for LiOH the reduction with Mg to Li plus MgO plus H2 is still thermodynamicaly favourable (but slightly less so).
Should the reduction of LiOH prove to be impossible with the t-alcohol catalysed mechanism, the more likely reason would be reduced solubility of Li
t-butoxide in non-polar solvents, vis-a-vis the solubility of K t-butoxide in equal conditions. That's an assumption, of course...
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garage chemist
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I have synthesized 2-methyl-2-hexanol about a year ago, but then neglected the potassium production and the little bottle of grignard-derived tertiary
alcohol has been gathering dust until now.
Just one hour ago I started a batch using 3g grignard-grade Mg turnings (in contrast to my successful batch that used fine Mg powder), 6g KOH and 1ml
tert-heptanol in 50ml Shellsol D70.
There was hydrogen and smoke production at the beginning but there's no potassium in sight one hour later. It doesn't seem to be a miracle catalyst.
Also, each drop of liquid that falls back into the flask from the dimroth condenser coil makes a little steam explosion. The alcohol clearly tends to
volatilize from the reaction mixture despite the 141°C boiling point.
If this batch works I could try sticking two carbons more on the catalyst molecule, but I would need 1-hexanol to prepare the alkyl bromide for the
grignard, and I don't have that.
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blogfast25
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GC:
It would be really strange if 2-methyl-2-hexanol was shown not to work!
I acquired dihydromyrcenol recently, which also is a 2-methyl t-alcohol, a C8 if I recall well, but haven't found time to test it yet...
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garage chemist
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Reaction mixture was left to cool after 3 hours of vigorous reflux and the solids inspected with spatula, forceps and by throwing portions of it into
water. Absolutely no potassium has formed, not even tiny particles. The magnesium was still present as mostly unchanged 1 mm sized grains surrounded
by initially melted and then solidified crumbly KOH.
Thus I found that even this catalyst doesn't allow potassium production with magnesium filings, at least when using the typical catalyst
concentration. This sucks since Mg powder is watched here and too risky to buy.
I could try a batch with increased catalyst concentration later.
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AndersHoveland
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Apparently under some reaction conditions, sterically hindered alcohols (such as tert-butanol) are much less vulnerable to reduction than
non-sterically hindered alcohols (such as isopropanol).
| Quote: |
The sterically hindered tertiary butyl group imparts stability compared to primary and secondary alcohols. As a result, the solubility and oxidative
stability characteristics provide many industrial applications as a reaction and process solvent and chemical intermediate. It is used as a
non-reactive solvent for chemical reactions.
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blogfast25
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garage chemist:
Wow, that's pretty disheartening news: if a C6 t-alcohol doesn't work, higher chain lengths aren't likely to fair much better. I wonder what the
problem here is: might the longer alkyl tail actually be getting 'in the way', making the OH group less accessible?
I wonder if you'd be willing to let me have a couple mL of your product, for corroboration on my part? Remember that Len1 years ago very decisively
stated that the t-butanol method didn't work and how he was proven completely wrong by POK and so many of us... For good science really someone should
confirm your results.
[Edited on 14-3-2012 by blogfast25]
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garage chemist
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I have a few ideas that I should try: preactivating the Mg by refluxing it in Shellsol with some tert-alcohol like NurdRage has shown is one of them,
as well as adding the catalyst in small portions over time during reflux.
I saw that NurdRage has had success with relatively coarse Mg turnings, which I find very remarkable since switching from powder to turnings did not
work for me at all.
Yes, I can send you some of the alcohol once I've made a few more experiments. Only about 20g are present here ATM but if I or you can get this to
work I will synthesize more of it.
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hames
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blogfast the percentage is around 87% I believe but the drum I got it out of says 99% tertiary butanol but I looked on the companies website (united
initiators)and it says their product is azeotropic tert butanol maybe they mean the 87% which is tba is 99% pure also it doesn't crystalize at 25
degrees.
garage chemist,could I use anhydrous magnesium sulfate as I have it on hand,I only have 150mls as its near impossible to buy I don't want to ruin it
so I might try it as is.
I've also decided that I'm going to try make a bit as well,I have heaps of n-butanol,can I make t-butanol from bromobutane in a grignard? and would I
then react the butyl magnesium bromide with acetone.
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blogfast25
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| Quote: Originally posted by garage chemist | I have a few ideas that I should try: preactivating the Mg by refluxing it in Shellsol with some tert-alcohol like NurdRage has shown is one of them,
as well as adding the catalyst in small portions over time during reflux.
I saw that NurdRage has had success with relatively coarse Mg turnings, which I find very remarkable since switching from powder to turnings did not
work for me at all.
Yes, I can send you some of the alcohol once I've made a few more experiments. Only about 20g are present here ATM but if I or you can get this to
work I will synthesize more of it.
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If I understand well (maybe not) you're now using a grade of Mg that hasn't given satisfaction in the past? I've only ever used one grade and it's a
fairly course powder, reagent grade. Never had to resort to 'activating'. If you're going to 'activate' the Mg, why not use IPA in a bit of Shellsol,
then discard the IPA/Shellsol, wash the Mg with clean Shellsol, then add the reagents/solvent?
Regards how to add the catalyst, as you probably know I'm convinced it can be added right from the start without need for the 'ritualised addition
sequence' which strikes me as chemical superstition. Several experiments show that 'one pot' works just as well w/o any discernible difference between
patent/POK and 'one pot'.
I'd love to test your alcohol at some point.
| Quote: Originally posted by hames | blogfast the percentage is around 87% I believe but the drum I got it out of says 99% tertiary butanol but I looked on the companies website (united
initiators)and it says their product is azeotropic tert butanol maybe they mean the 87% which is tba is 99% pure also it doesn't crystalize at 25
degrees.
garage chemist,could I use anhydrous magnesium sulfate as I have it on hand,I only have 150mls as its near impossible to buy I don't want to ruin it
so I might try it as is.
I've also decided that I'm going to try make a bit as well,I have heaps of n-butanol,can I make t-butanol from bromobutane in a grignard? and would I
then react the butyl magnesium bromide with acetone. |
hames: as a starting point I would try the alcohol as such. Should it not lead to the desired result, try drying. Just my two cents...
Bromobutane grignarded with acetone would give you 2-methylhexan-2-ol, not t-butanol, which is what garage chemist did.
Using bromoethane grignarded with acetone gives 2-methylbutan-2-ol (aka 2M2B), the only other (besides t-butanol) tertiary alcohol that we know for
certain also works: I use it instead of t-butanol.
[Edited on 14-3-2012 by blogfast25]
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garage chemist
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I'm not using the turnings that didn't work before (those were selfmade), I'm now using "grignard grade" 99,8% Mg turnings, and I haven't tried these
before.
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garage chemist
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New batch is running. This time, 40ml Shellsol D70 was used, and 3g grignard Mg turnings were refluxed in it with addition of 0,3ml tert-heptanol for
30 minutes. After this, the solvent was slightly turbid.
It was left to cool slightly, and 6g KOH were added.
After resuming heating, there was vigorous bubbling and smoke evolution, and then all of a sudden the mixture frothed up and emitted blue smoke out of
the condenser. There was also blue froth being thrown up until the top of the condenser, the mixture assumed a blue color for just a few seconds and
then returned to turbid yellowish. I was very surprised, this was the first time I saw something emitting blue smoke unexpectedly!
I added another 0,3ml tert-heptanol and continued refluxing.
Let's see what this witches' brew will do next. Has anyone ever seen this reaction produce a blue smoke and froth?
The new catalyst seems to be doing at least something ...
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blogfast25
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Understood on the new Mg.
But blue smoke?!? Holy Moly...
Let's see if any K results. Your t-heptanol was purified properly, right? I'm thinking residual bromobutane might wreak havoc with any formed K but
that's just speculation right now.
Could the blue be finely dispersed fresh K?
[Edited on 14-3-2012 by blogfast25]
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garage chemist
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The tert-heptanol was isolated and purified to the best of my skill and knowledge, and I am quite sure it does not contain any residual bromobutane.
The product was constant boiling, and the forerun was the azeotrope with water which was dried and redistilled.
The blue froth did not react violently with water, it didn't even bubble.
The batch looks very different now than the last time, it went kinda "dark", like my successful batch. I broke up the hard solid cake with a spatula,
added another 0,3ml tert-heptanol and continued refluxing. It looks as if there are tiny potassium droplets forming.
Breaking up the solids and stirring during the reaction seemed to really speed things up, seems like this is important with coarse Mg.
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blogfast25
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| Quote: Originally posted by garage chemist |
The batch looks very different now than the last time, it went kinda "dark", like my successful batch. I broke up the hard solid cake with a spatula,
added another 0,3ml tert-heptanol and continued refluxing. It looks as if there are tiny potassium droplets forming.
Breaking up the solids and stirring during the reaction seemed to really speed things up, seems like this is important with coarse Mg.
|
In my experience, coalescence of any formed K into globules is what takes by far the longest time with this method. Not sure whether this is affected
by Mg granulometry.
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garage chemist
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Results: only an extremely small amount of potassium has formed, just two or three 1mm-sized spheres. Most of the magnesium and KOH was still
unreacted.
The flask was also heavily attacked by the molten KOH and now has a crack on the bottom, so it has to be thrown away.
Potassium has started forming early but the reaction then stopped dead in its tracks. Very strange.
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blogfast25
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It certainly is very strange. Annoying also, this kind of 'halfway house' result... In any case it doesn't seem to constitute an improvement over
t-butanol or 2M2B.
That 'glitch' at the start keeps bothering me though...
[Edited on 15-3-2012 by blogfast25]
[Edited on 15-3-2012 by blogfast25]
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Lambda-Eyde
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| Quote: Originally posted by garage chemist | Results: only an extremely small amount of potassium has formed, just two or three 1mm-sized spheres. Most of the magnesium and KOH was still
unreacted.
The flask was also heavily attacked by the molten KOH and now has a crack on the bottom, so it has to be thrown away.
Potassium has started forming early but the reaction then stopped dead in its tracks. Very strange.
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That's disappointing, gc. Both on the results and on the fate of your flask. I'm worried about damaging my ground glass erlenmeyers when I decide to
have a go at this reaction. At the moment I only have grignard magnesium (but no ether  ), but I'm also getting some powder soon. I'll be trying out both, together with paraffin and some really old KOH.
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