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Author: Subject: 1,3 propanediol from D- panthenol
Niter of Potash
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[*] posted on 15-10-2017 at 02:07
1,3 propanediol from D- panthenol


Recently, I found that I can easly obtain D-panthenol from "DIY cosmetics" store. It is used as moisturizer in cremes etc.

When I saw structure, I immediatly realised that I can hydrolise amide bond, obtain 3-propanolamine, and treat propanolamine with H2SO4/NaNO2 to turn amine to alcohol, yielding my desired 1,3 propanediol.

So, I bought 100g package (not cheap - approx. 10$), weighted out 20-ish g of D-panthenol, mixed that with 30ml H2O + 26g NaOH, mixed up everything and heated it up in a beaker for 2-3 hours, at arround 60-80 degrees. I didn't realy want to heat up mixture a lot higher to prevent 3-propanolamine evaporation.

Ammoniacal odor was evident, but no upper layer (my guess is that NaOH would salt-out propanolamine), neither any crystalline product percipitated.

On cooling, mixture turned back to pretty viscous, colorless goo, so i'm pretty shure that most of D-panthenol is still unreacted.

So, does anyone have tips/adjustments to my method?

If 3-propanolamine can't be salted out, is there some other simple extraction method (maybe toluene extraction? it's only water-immiscble solvent I can get in large quantaties cheaply), or maybe even boiling mixture in steel can, and just letting 3-propanolamine and water come over as it is produced?
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Metacelsus
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[*] posted on 15-10-2017 at 06:30


If you just need the 1,3-propanediol and don't care how you obtain it, you could just buy it (it's available on Amazon and Ebay). Overall, this would almost certainly be cheaper than making it yourself.



As below, so above.
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clearly_not_atara
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[*] posted on 15-10-2017 at 09:36


From SA the bp of 3-aminopropanol is 184 C so you shouldn't see too much loss from boiling water. If you're worried about it you can use a reflux condenser but that might not be necessary.
The byproduct 3,3-dimethyl-2,4-dihydroxypentanoic acid is somewhat soap-like and may inhibit attempts at salting out the propanolamine. Extracting the solution with DCM or similar might still work even if no separation is visible.
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Niter of Potash
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[*] posted on 19-10-2017 at 11:39


Quote: Originally posted by Metacelsus  
If you just need the 1,3-propanediol and don't care how you obtain it, you could just buy it (it's available on Amazon and Ebay). Overall, this would almost certainly be cheaper than making it yourself.



As NurdRage says, "our objective here is to explore science" ;)

I might try small scale (~10g of panthenol) acid catalysed hydrolisis(HCl,most likely), to avoid forming 3,3-dimethyl-2,4-dihydroxypentanoic acid/ sodium salt. If i'm lucky, some of that acid might precipitate or crystalise on cooling, and after that I might freebase my amine and isolate it.


How long sould I heat/reflux mixture to get reaction close to completion? Would 1-2h be enought, or amides take longer to hydrolise?
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clearly_not_atara
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[*] posted on 19-10-2017 at 12:14


I would say 24 hours, based on others' experience with amides like DEET. If you don't feel comfortable refluxing the mixture while you sleep you can do it in stages or just do a 14 hour rxn all day

[Edited on 19-10-2017 by clearly_not_atara]
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[*] posted on 9-12-2017 at 05:08


UPDATE:

I decided that NaOH method just isn't worth the effort of separating products, so i threw it away.

So, to proceed with my synthesis, I mixed all D-panthenol I got left (approx 83g) with 250g ~20% H2SO4. Then, I heated mixture to near boiling, in 600ml beaker, and kept it at that temperature for a few hours (3-4h, I forgot exact number).

After heating, I was left with something like 200ml of clear liquid.
After a week or so, there was no crystaline product in beaker yet.

Then, I had to abandon this reaction mixture for a month or so. When I came back, a lot of needle-like crystals crystalised out of solution.

So yesterday I filtered off those crystals.
I got approx. 150ml of solution, and for now unknown quantaty of crystals. Sadly my lab scale is dead, so I can't weight those crystals.

Crystals are somewhat similar to urea or benzoic acid crystals. They are dry to touch pretty quickly, after just a few minutes under vaacum on my sinter funnel.

Next step will be to determine what those crstals are. I expect them to be that carboxylic acid from D-panthenol, and not 3-aminopropanol sulfate.
3-aminopropanol sulfate should be extremly water soluble, so I expect it to stay in solution.

I plan to mix few grams of those crystals with conc. NaOH solution. If mixture won't have ammoniacal odour, I will be pretty confident that desired 3-aminopropanol is still in soltion.

Also, I might try dissolving some of them in varois solvents (acetone, ethanol, toluene, ethyl formate, glacial acetic/formic acid acid...). That might help me determining what those crstals are - "acid part" of D-panthenol or 3-aminopropanol sulfate.

Theoreticaly, I sould have 59g of that carboxylic acid.
If most of it is crystalised out of solution allready, I will proceed to next step - treating 3-aminopropanol sulfate with KNO2 to get 1,3 PD.
If not, I will first try to get some more of those acid crystals to come out of solution,most likely by boiling off 50ml of water from my filtrate.

Any suggestion on how to determine what those crystals are, or adjustments/suggestions considering my work-up?

I attached picture of those crystals. They are slightly sticky, most likely because I havent really dryed them completly.



25138985_1584098644958623_1939722424_o.jpg - 177kB
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[*] posted on 9-12-2017 at 08:54


That's interesting. You might also consider the possibility that you have a sulfuric acid ester.



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[*] posted on 9-12-2017 at 16:40


Just to make it clear, the acid component of D- panthenol is:

(2R)-2,4-Dihydroxy-3,3-dimethylbutanoic acid
and not
3,3-dimethyl-2,4-dihydroxypentanoic acid

AvB
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[*] posted on 10-12-2017 at 17:54


Quote: Originally posted by AvBaeyer  
Just to make it clear, the acid component of D- panthenol is:

(2R)-2,4-Dihydroxy-3,3-dimethylbutanoic acid
and not
3,3-dimethyl-2,4-dihydroxypentanoic acid

AvB


Thanks!
I guess that's why I couldn't find any usefull data about that acid.
Seems like that (2R)-2,4-Dihydroxy-3,3-dimethylbutanoic acid has got shorter,nicer name - pantoic acid.
It should have melting point arround 82 degrees C, so I can test that as well.
Also, according to ChemSpider, it should have solubility of arround 37,8g/100ml, at 25 deg. C. That means that I should have arround 22g, or slightly more of crystals, assuming that reaction is more or less pushed towards completion.
I will probbaly measure MP and weight of crstals in a week or so.


I don't think that there is much aminopropanol-sulfuric acid ester formed,since there is still plenty of water in solution.

Sadly, I can't find any data on 3-aminopropanol sulfate solubility in water or any other solvent. Crushing it out of solution with EtOH,iPrOH, some similar solvent, or extracting with some solvent might be good way to get rid of pantic acid.

If I don't find any good and simple way to isolate 3-aminopropanol sulfate, I will just add KNO2 solution in this reaction mixture, neutralise or slightly basify solution with NaOH, filter off anything that crystalises out of solution and separate 1,3 propanediol from water and solid reaction byproducts (Na and K sulfates and pantoates) by distillation, or maybe extraction if I have proper solvent at hand.

I hope that there won't be any compound that might cause 1,3PD to form ether/polymer with itself, since ethylene glycol can be easly turned into 1,4 dioxane with just some sulfuric acid.

[Edited on 11-12-2017 by Niter of Potash]

[Edited on 11-12-2017 by Niter of Potash]
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[*] posted on 19-12-2017 at 07:58


UPDATE:

Weight of crystals is 28g. That is more or less what I expected, since temperature in my lab was something like 10 deg. C.

Upon mixing them with strong NaOH solution, no ammoniacal odour was evident.
As control, I added a little bit of solution containing my desired 3-aminopropanol sulfate. Ammoniacal odour was immediatly evident.

So, I splitted my solution containing 3-AP sulfate in 2 equal batches. I will store one for now, just in case that I screw up work-up first time.

Then, I calculated that I need 20g of potassium nitrite to convert 16g of 3-aminopropanol wich sould be in mixture to 1,3-propanediol via diazonium salts. I dissolved that nitrite in about 50ml of water, and slowly, dropwise added it to mixture. Quite a bit of bubbling appeared after every drop, and just a little bit of NO2 was formed, so I guess I did this corrcetly.
I think that this step could be improved by diluting original solution a little bit, and cooling it down to 0 deg. C (this time, temperature of solution was arround 10 degrees)

Quite a bit of very fine white percipitate formed, most likely potassium salt of pantoic acid. It took me like 2 hours to filter just 120ml of solution. For now, I will keep it, just like I will keep pantoic acid. I plan to make 2,2 dimethylmalonic acid from it.

So now I got solution of what should be 1,3 propanediol, water, sulfuric acid and maybe just a little bit of pantoic acid. Here are few ideas for next step:

1) Neutralise all acids, filter off any salts wich might form, and separate 1,3PD from water by distillation
2) Instead of distillation, I might even try to salt out 1,3PD. Sadly NaOH and NaCl are only salts I got in lage enought quantaties.

3) Instead of neutralising acids, I might extract 1,3PD from water using some solvent. Now I don't have much to choose from - esters would most likely hydrolise, and only water-immiscible solvents I got left are toluene, xylene and a little bit of diethly ether which I want to save for some grignard reactins I have in plan.

For now, I prefer option 3, but first I'd like to know how effective toluene is in such extraction (diol from water). If it is good enought, I might do 3 extractions (something like 15ml + 2x 10ml of toluene).
If this works, it would be huge improvement over other 2 methods - I would have to distill much smaller volume later, and it doesnt' involve using rather huge amounts of NaOH to work.

In worst case, even using same amount of diethyl ether is somewhat acceptable to me, but still, I wolud prefer toluene,if it is good enought.

Does anyone here have experience in such extractions(alcohols/diols from water using toluene, or ether)?



[Edited on 19-12-2017 by Niter of Potash]
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thumbdown.gif posted on 28-12-2017 at 06:00


[CONCLUSION]

In the end, toluene extraction failed completly, so I just neutralised everything, filtered off Na2SO4 wich crystalised from solution, and then I started distilling off water. I had to stop distillation 3-4 times to filter off Na2SO4 that fell out of solution, causing liquid in boiling flask to bump a bit too much.

In the end, my final "yield" is 5-6ml of some off-coloured, very viscous (glycerol-like) liquid wich boiled above 120 deg. C. As vapour temperature rised towards 200 deg. C, and slightly above, content of flask rapidly turned black, quite a bit of fumes escaped from my condenser and distillate(or maybe just stuff that "jumped" from flask) became orange-brown in colour.

At this point, I quickly turned off my torch wich I used for heating, and stopped distillation.

Before final distillation, I had approx. 20ml of rather viscous, reddish-orange liquid. This colour is most likely due to some lead oxide in my KNO2, and phenolphtalein wich I used when I was neutralising reaction mixture.
Some water boiled off first - maybe 5-8ml. So, if everything vent fine, I would expect 12-15ml of 1,3PD - arround 50% yield, and that would be fine. However,looks like that something caused 1,3PD to form ether(s). It might be that some sulfuric acid or sodium bisulfate remained in solution and triggered this reaction.

Clean-up of my equipment is not that hard - acetone,toluene and ethanol were basicly useless, and some NaOH solution did the job rather good, just like cleaning equipment after 1,4 dioxane synthesis, so that is pretty good sign that I acctualy had 1,3 propanediol wich just got destroyed in my last step.

In conclusion, this seems to be one viable route of making 1,3 PD, but only if you are really desperate to get some 1,3 PD. Also, purification of 1,3PD must be improved first.
I guess that leaving it in aqueous solution is best if you don't need pure 1,3PD. Coloured impurities might be removed with activated carbon, and distillation should be done under vaacum. Sadly, I don't have setup to do that, so this is probally it.

Unless I realise why exactly 1,3PD got messed up,I don't think that I will re-do this experiment.
D-panthenol is somewhat expensive, and this procedure takes pretty long time to finish.
Basicly, only somewhat usefull product I got is pantoic acid.

Since my desired final product is acctualy malonic acid, I will try another route - reacting beta-allanine with KNO2, and then just oxidise formed 3-hydroxypropionic acid with HNO3, evaporate solution and extract malonic acid from inorganic salts with ethanol, ether or some other solvent. Conc. formic and acetic acid might be good solvents as well - cheaper than ether, and there is no way they will form esters with malonic acid.

If I go this route, I will not even attempt to purify or isolate 3-hydroxypropionic acid, since it decomposes upon distillation.



[Edited on 28-12-2017 by Niter of Potash]

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[Edited on 28-12-2017 by Niter of Potash]
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