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blogfast25
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That's not the end of it: this is a hydrogenation. It's outside the envelope for most home chemists.
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elementcollector1
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Please explain. Napthalene is first hydrolyzed to tetralin, then on to decalin; and the person in question has done this before. The amounts of
reactants are apparently enough to ensure hydrogenation to tetralin without too much decalin being formed. Then the mix is fractionally distilled to
afford the desired compound.
Being an inorganic chemist, you're probably right and there probably is some huge hole in this procedure that I overlooked. But do explain what that
hole is, because otherwise I wouldn't know if there is one.
Elements Collected:52/87
Latest Acquired: Cl
Next in Line: Nd
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blogfast25
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See tetralin wiki entry. Possibly 'the person in question' (do you mean nurdrage?) followed a different route but industrially it's catalysed
hydrogenation of naphthalene.
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plante1999
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If someone have a procedure for naphthalene hydrogenation I could try it since I have naphthalene, 5% Platinized asbestos and a way to generate
hydrogen. I'm not much into organic's so I don't really know how hydrogenation work but I can do the synthesis If I learn how hydrogenation work.
I never asked for this.
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elementcollector1
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It's not nurdrage, although it was a post on the instructables link to his 'Potassium Metal' synth.
Tetralin wiki throw gives "hydrogenation of napthalene over a platinum catalyst," and then a few different transition metal mixes that can be used
under pressure. Does that mean I have to throw some platinum in the mix for it to work at all?
Elements Collected:52/87
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plante1999
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Quote: Originally posted by elementcollector1  | It's not nurdrage, although it was a post on the instructables link to his 'Potassium Metal' synth.
Tetralin wiki throw gives "hydrogenation of napthalene over a platinum catalyst," and then a few different transition metal mixes that can be used
under pressure. Does that mean I have to throw some platinum in the mix for it to work at all? |
Platinum is NOT platinum catalyst, It need to be very finely divided platinum form such as platinum on alumina, platinum on carbon or platinum on
asbestos. I would not recommend transition metal catalyst for an home chemist.
[Edited on 26-9-2012 by plante1999]
I never asked for this.
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Mailinmypocket
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Well after a few more attempts using several types of solvents (heavy hydrotreated naptha, hypoallergenic baby oil, "odorless art solvent, and
kerosene) and two types of Mg (firestarter shavings and the lab grade "flame retardent" coated granules which have been ground or activated) I have
found no real success.
Once again I bit the bullet and ordered some reagent grade fine Mg turnings and reagent grade KOH (not necessary but I'm getting frustrated and want
to rule out any possible interference).
If THAT doesn't work, then I'm going to have a nervous breakdown  Should receive
that this week and will report back on the results. Fingers crossed.
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blogfast25
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Very disappointing and somewhat mystifying, MMP...
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Mailinmypocket
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I know... But on the plus side I think I have learnt a lot more by doing research after every failure as opposed to having it work on the first try
I should have the new reagents in about a week and then will be the true test!
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zbret
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I'm guessing everyone's seen this by now, but just in case you haven't - NurdRage on YouTube shows the production of potassium metal and uses a high
boiling solvent and tertiary alcohol. He mentions in the video the importance of each. After much searching for any tertiary alcohols, I gave up
looking, never mind the also tricky to find high boiling point solvent.
watch?v=gHgyn-wsxFw
He also shows how to coalesce the blobs as well, which is also interesting to watch:
watch?v=xzkajgxVbyI
[Edited on 8-10-2012 by zbret]
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blogfast25
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| Quote: Originally posted by zbret | I'm guessing everyone's seen this by now, but just in case you haven't - NurdRage on YouTube shows the production of potassium metal and uses a high
boiling solvent and tertiary alcohol. He mentions in the video the importance of each. After much searching for any tertiary alcohols, I gave up
looking, never mind the also tricky to find high boiling point solvent.
watch?v=gHgyn-wsxFw
He also shows how to coalesce the blobs as well, which is also interesting to watch:
watch?v=xzkajgxVbyI
[Edited on 8-10-2012 by zbret] |
We know: read the thread. Nurdrage is on it.
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UnintentionalChaos
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When it comes to using kerosene, don't bother with Coleman brand in the blue bottle in your local camping depatment of walmart.
It was refluxing furiously at only about 185C, tops. It was a small run and I decided to proceed anyway despite this. After t-BuOH addition, the
reflux temperature fell and stayed around 160C. Unsurprisingly, no potassium resulted. I'll fractionate the stuff later and remove the lower boiling
components.
Department of Redundancy Department - Now with paperwork!
'In organic synthesis, we call decomposition products "crap", however this is not a IUPAC approved nomenclature.' -Nicodem
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metalresearcher
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I also tried this method by using lamp oil and KOH + Mg shavings in it.
Heating 2 hours to 200ºC did not result in any K metal. Putting the residue in water did not result in any reaction.
But, KOH + Mg in a steel tube retort and then heating to start the reaction did result in small amounts of K. Here a video of it:
<iframe sandbox width="640" height="360" src="http://www.youtube.com/embed/qxS9uKvHWks?hl=en_US" frameborder="0" allowfullscreen></iframe>
[Edited on 2012-10-12 by metalresearcher]
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blogfast25
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Yes, that magnesiothermic reaction of KOH with Mg has been shown to work on this forum sevaral times. Problem is: metal recovery is difficult because
you obtain a sintered mix of metal and MgO.
You could try covering the post-reaction mixture with Tetralin, then prize that mix out of the crucible, then gently heat it to about 90 C: molten
potassium reportedly (Nurdrage) floats on Tetralin.
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Polesch
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I came across this book "Small-Scale Synthesis of Laboratory Reagents - with Reaction Modeling" by Leonid Lerner, CRC Press. Which talks about this
synthesis procedure in one of the chapters, which you can download here. The part of the chapter talking about KOH reduction in paraffin,
It references to this patent for the procedure.
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DJF90
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Len is a member here and contributed somewhat to this thread, probably where he got the synthesis from for his book.
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watson.fawkes
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| Quote: Originally posted by DJF90 | | Len is a member here and contributed somewhat to this thread, probably where he got the synthesis from for his book. |
"Somewhat" and "probably" are understatement. He tried the synthesis years ago, failed utterly, and very loudly declared it busted.
Also, I'd be careful of believing his reaction scheme as listed. It's plausible, certainly, but to my knowledge, it's unproven. The main difference
between his failed experiment and the successful ones here was the geometry of the reaction, basically stirred vs. still. If it were simply a matter
of an intermediated redox reaction and solubility, it would seem that the geometry wouldn't matter. Yet it does. In my opinion, the reaction pathway
remains unproven. There's still some science left to be done here.
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DJF90
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Sorry to irk you watson, I spoke without refreshing my memory. I thought the whole scenario was quite amusing to be honest.
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watson.fawkes
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| Quote: Originally posted by DJF90 | | Sorry to irk you watson, I spoke without refreshing my memory. I thought the whole scenario was quite amusing to be honest. |
Oh, not to worry, I'm not irked. I just wanted to ensure the anecdote wasn't minimized.
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blogfast25
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| Quote: Originally posted by watson.fawkes | "Somewhat" and "probably" are understatement. He tried the synthesis years ago, failed utterly, and very loudly declared it busted.
Also, I'd be careful of believing his reaction scheme as listed. It's plausible, certainly, but to my knowledge, it's unproven. The main difference
between his failed experiment and the successful ones here was the geometry of the reaction, basically stirred vs. still. If it were simply a matter
of an intermediated redox reaction and solubility, it would seem that the geometry wouldn't matter. Yet it does. In my opinion, the reaction pathway
remains unproven. There's still some science left to be done here. |
He did eventually get the thing to work, in this thread. There were other differences between his original failed experiment and the later successful
one, other than mere scale: in the original experiment he used fairly high speed stirring provided by an overhead motor and stirring rod/paddle. Most
successful [with this reaction] experimenters scaled the reaction down from the original patent. I don’t think scale is a real issue here.
To the proposed reaction mechanism some elaborations have been added since: as it stands today it may not be perfect but it’s the best we’ve got,
IMHO…
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watson.fawkes
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| Quote: Originally posted by blogfast25 | He did eventually get the thing to work, in this thread. There were other differences between his original failed experiment and the later successful
one, other than mere scale: in the original experiment he used fairly high speed stirring provided by an overhead motor and stirring rod/paddle. Most
successful [with this reaction] experimenters scaled the reaction down from the original patent. I don’t think scale is a real issue here.
To the proposed reaction mechanism some elaborations have been added since: as it stands today it may not be perfect but it’s the best we’ve got,
IMHO… |
He certainly did get it to work; it's in his book. The stirring was the main geometric difference I
see. Part of this is an effective increase in the amount of solvent per particle and consequent particle separation. This is what seems to matter,
causing the reaction to fail.
As for reaction mechanism, I did already say that it was plausible. Yet it's also unproven, and I find reason to doubt it. If it were just a matter of
solubility, the stirred reaction should have worked. So I think there's some kind of short-lived intermediary involved, given that the diffusion time
(between KOH and Mg) was the main difference. Short-lived means there's a competing reverse reaction. None of the steps in the proposed reaction
scheme are reversible in that way. One alternate would be an adduct between KOH and the alcohol. If the adduct breaks up in solution, the KOH would
accrete back onto one of the particles, which means that the alcohol would also have to have some activity when adsorbed onto the Mg surface
(otherwise it would simply react when it accreted onto Mg). I don't find this explanation more plausible, mind, but it does match one
experimental aspect that the proposed one does not.
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blogfast25
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Watson:
There has recently been a spat of failures reported here, caused by unknown problems. Len’s initial failure may have also been due to one of these
unknown factors, regardless of the stirring issue. I think it was you who introduced the idea of a ‘Goldilocks situation’ with regards to this
reaction and that seems to be true at least in a sense: various experimenters that seem to have ‘done everything right’ failed to produce any K.
With regards to solubility, we have one (but uncorroborated) data point suggesting solubility isn’t an issue: garage chemist’s experiment with a
longer chain tertiary alcohol which yielded nothing. Our expectation based on solubility that a C6 t-alcohol would speed up reaction (and possibly
make sodium synthesis much shorter) didn’t materialise. One problem is that no one tried to replicate GC’s no-show results.
As regards adducts tp KOH, it’s possible of course. But since as we know of 2 alcohols that work we’d have to assume both form similar adducts.
[Edited on 20-10-2012 by blogfast25]
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watson.fawkes
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| Quote: Originally posted by blogfast25 | | There has recently been a spat of failures reported here, caused by unknown problems. Len’s initial failure may have also been due to one of these
unknown factors, regardless of the stirring issue. |
Point taken.
It seems like we're at the point where we need exhaustive experimental descriptions from all the trials both succeeded and failed. It's unlikely that
we'll get those retrospectively, unfortunately. That's not just the reagents used, but also the glassware, heating schedules, etc. Welcome to
research, I suppose.
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Mailinmypocket
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Update: Today would have been the moment of truth...
But my supplier tells me that there is still a back order on the KOH, and it will ship this week. It was supposed to ship LAST WEEK.
Such are the joys of chemical orders I suppose.
Haven't given up on this, just running into delays 
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blogfast25
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| Quote: Originally posted by Mailinmypocket | But my supplier tells me that there is still a back order on the KOH, and it will ship this week. It was supposed to ship LAST WEEK.
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There does actually appear to be a bit of a supply problem with KOH for the moment, resulting also in a price hike...
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