menchaca
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pentaerythritol from methanol and ethanol
hello! i´ve thinking that maybe possible get pentaeretrithol using a mixture of ethanol and methanol, oxidiying it in basic media maybe with KMnO4
and NaOh or something so.. of course this is just a idea and don´t know at all if this would work or not i really don´t see why this wouldn´t,
but.. well some idea? Thanks!!
Edit: Title spelling.
[Edited on 4-3-2005 by chemoleo]
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PrimoPyro
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Onepot = no
I don't think it can be done in a one pot,and you will have problemswith oxidation using KMnO4, it has a tendency to oxidize alcohols to acids.
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menchaca
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well the oxidicer was just an minor important detail for me i was more interested if this was possible to make it directly from methanol and ethanol.
what about other oxidicers MnO2, K2Cr2O7..
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chemoleo
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I think there was another thread on pentaerythritol
... KMnO4 indeed will oxidise ethanol to acetic acid, and you can obtain H2CO easily OTC, so no need to bother with this...
Now, acetaldehyde can be made with the K2Cr2O7 method, again I think it was mentioned in the Acetaldehyde thread.
Once you got those two reasonably clean, you can roll 
Another reason why that two in one approach would likely not work (say, if you used the perfect oxidiser that would only form the aldehydes, but no
acids) is that you would get side products, and quite a few of them. For instance, nascent acetaldehyde would potentially react with unreacted
methanol to form acetals (hell, it would of course react with ethanol itself too). Many other reactions are possible, not just the pentaerythritol
one.
To retrieve reasonably pure H2CO and CH3CHO from it would be quite a task.
Also, the aldehydes are generally formed under acidic condtions (i.e. with dichromate), while the pentaerythritol reaction takes place under basic
conditions (in the presence of Ca(OH)2).
So better make those aldehydes separately I should think
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menchaca
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well is just a pity.... it would have been so beautiful....snif,snif thanks all
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vulture
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KMnO4 acts as an oxidizer in basic media too. You'll just have to find the right redox sequence.
How bout MnO2? Much more selective.
One shouldn't accept or resort to the mutilation of science to appease the mentally impaired.
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PrimoPyro
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Well, How about this?
The main reason I don't think your idea will work is because methanol, when oxidized to formaldehyde, will not stop. KMnO4 easily oxidizes
formaldehyde to formic acid.
The reaction of acetaldehyde and formaldehyde to form pentaerythitol is called the Tollins reaction, and I detailed it very specifically at the
E&W Forum over a year ago.
The reaction uses calcium hydroxide as a catalyst, and there is a careful equilibrium between the alcohols and some byproduct formic acid. By having
so much more formic acid in solution from oxidation of formaldehyde, the equilibrium is changed.
Also, excess acids in solution will destroy the needed hydroxide ions to start the reaction.
A better route would be to use dehydrogenation instead of oxidation of the alcohols. Unfortunately this increases the cost and also lowers the
over-the-counter-ness of the reaction.
But what about not making PETN exactly? Don't you think that the exact same compound, with one of the leg -CH2ONO2 groups changed to a -CH2NO2
(elimination of an oxygen, changing the nitrate to a nitro compound) should also be very powerful? I think so. This is much easier to make if you
can't get acetaldehyde.
The same Tollins reaction, replacing acetaldehyde with nitromethane, will yield the compound I described above.
PrimoPyro
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Mumbles
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Just a theory, but what about mixing the components and vaporising. Then pass the vapors over hot Copper filings to reduce both to the respective
aldehydes? I know that dehydrogenation only goes to the aldehyde stage. So the over oxidation would be prevented. They're both soluble in
water so it may be a suitable solvent.
I really don't know if the diluted chemicals would work though. Maybe keep the temp in the recieving receptical cold enough to condense the
acetaldehyde and bubble the resulting Formaldehyde into water. React then. It all would work in theory.
[Edit] Damn, I swear the stuff about dehydrogenation mentioned by PrimoPyro wasn't there 5 minutes ago.
[Edited on 11-4-2003 by Mumbles]
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KABOOOM(pyrojustforfun)
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<blockquote>quote:<hr>But what about not making PETN exactly? Don't you think that the exact same compound, with one of the leg
-CH2ONO2 groups changed to a -CH2NO2 (elimination of an oxygen, changing the nitrate to a nitro compound) should also be very powerful? I think so.
This is much easier to make if you can't get acetaldehyde. <hr></blockquote>
actuelly with one of the leg -CH2ONO<sub>2</sub> groups changed to a <b>"-NO<sub>2</sub>"</b> thus OB is
perfect!:
O<sub>2</sub>N-C(-CH<sub>2</sub>ONO<sub>2</sub> <sub>3</sub> <s> ></s> 4CO<sub>2</sub> + 3H<sub>2</sub>O +
2N<sub>2</sub>
it's a liquid exlosive with a VOD of 7860 m/s. megalomania's site has recepies for both NIBGTN and trimethylolnitromethane.
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Rosco Bodine
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| Quote: | Originally posted by menchaca
hello! i´ve thinking that maybe possible get pentaeretrithol using a mixture of ethanol and methanol, oxidiying it in basic media maybe with KMnO4
and NaOh or something so.. of course this is just a idea and don´t know at all if this would work or not i really don´t see why this wouldn´t,
but.. well some idea? Thanks!!
Edit: Title spelling.
[Edited on 4-3-2005 by chemoleo] |
I stole your idea  Sue me 
Anyway , it is a good idea and there could be a way .
Recently there is interest in an electrolytically produced
manganic oxidizer , which might be worth experimentation ,
for a mixed alcohols oxidation to their respective aldehydes
needed for pentaerythritol .
It would be beautiful if it works .
If simultaneous oxidation of the mixed alcohols is
complicated by unwanted side reactions , then it
should still be possible to form the aldehydes separately ,
by dividing the bulk manganic reagent into proper
proportions , performing the oxidations and filtrations
in separate vessels , and then combining the liquids
for the production of the pentaerythritol .
[Edited on 31-10-2006 by Rosco Bodine]
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chemoleo
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One problem I can see right off..... alcohols react with aldehydes to form acetals. The yield will be undoubtedly lowered because of formation of
acetals during the oxidation by manganous alum, because nascent CH2O/CH3CHO can react directly with alcohols that are still present.
Nonetheless I think it's an idea worth pursuing...maybe not in the context of a one pot synth of PE, but acetaldehyde or formaldehyde to start off
with.
The problematics of this reaction depends a lot on the reaction rates of acetal formation. Since formaldehyde is easily available (at least here in
the UK, when I bought it 6 years ago from farm supplies), why not just oxidising ethanol on its own? I'd love to see the efficiency of the reaciton.
The alternative reaction with potassium dichromate works too but is not regenerable, requires destillation, and is prone to overoxidation to acetic
acid. I wonder if manganous alum is simply a better oxidant. I shall be testing the making of this compound shortly, since I now have a lovely power
supply.
Never Stop to Begin, and Never Begin to Stop...
Tolerance is good. But not with the intolerant! (Wilhelm Busch)
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Rosco Bodine
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Another potential problem is polymerization of the aldehydes from the sulfuric acid formed by the oxidation . It would also be in the filtered liquid
from the oxidation to complicate things . So on second thought ,
this would probably not work as a one pot reaction .
The oxidation would have to be run warm and with the
slurry thin enough to allow the acetaldeyde to boil out
freely as fast as it forms , and be distilled out of the reaction mixture , perhaps absorbed by bubbling the vapor directly into crushed ice and water
, in a flask
sitting in a salted ice bath .
Acetaldehyde is really the important component to gain here , since paraformaldehyde or trioxane are easily available and easily converted to formalin
.
So if all we can do is get an efficient method for acetaldehyde , then this manganic oxidation scheme
is a valuable tool for synthesis of the pentaerythritol .
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The_Davster
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But acetal formation is an equilibrium reaction, you have to activly remove water by dean starking or whatever method.
A while ago I tried a refluxing mix of EtOH, MeOH and CaOH, with a glowing Pt wire just below and to the side of the reflux collumn. I figured this
method perhaps viable, but the damn thing kept catching on fire, as I took no precautions to exclude O2.
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Cloner
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The canizzaro reaction to PE is a bitch to work up. In the end you will have a lump which contains PE and may need further purification. If there's
not much else in there to begin with, you can get an adequate quality of PE. But if you add side products of previous reactions it will be much worse.
[Edited on 1-11-2006 by Cloner]
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Sauron
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There's lots to do with pentaerythritol once one has it that aren't as antisocial as PETN.
Spiro compounds come to mind, spirolactones for example. Often very pretty molecules.
If one wants to eschew handling fots of formalin, there's paraformaldehyde and tere's trioxane, much more convenient. I don't recall the particulars
of whether or not they can be employed to advantage in the prep of PE but then I haven't looked at this rxn in several decades
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jon
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PARAFORMALDEHYDE AND TRIOXANE will easilly hydrolyse in the prescence of a base there was a discussion about this some time ago but there is an
optimal amount of base to use , as too little = no hydrolysis, and too much canizzaro reactions.
B.T.W. i remember seeing a PETN synth using hexamine and nitric acid does this work?
[Edited on 23-12-2006 by jon]
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Sauron
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I believe that's the usual path to RDX etc not to PETN. The former is a nitramine, the latter is not. Hexamine (urotropine, HMTA) does have a number
of synthetic uses, generally as a formaldehyde source but getting to PE does not seem likely to be among them. It'd be going to Seattle to get from
NYC to Buffalo.
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