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Author: Subject: Acetaldehyde synthesis
Hawkguy
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[*] posted on 10-12-2015 at 16:17


Quote: Originally posted by nux vomica  
Quote: Originally posted by Hawkguy  
Quote: Originally posted by nux vomica  
Yes its a mix of unreacted ethanol and acetaldehyde, I collect the distillate that comes off below 60° c but it would be better to know the % of acetaldehyde in the solution so I can calculate how much to collect , and to check purity of the final product.


Try making paraldehyde and measuring it that way


I will have to look into that method, as I already use the sodium sulfide method with my formaldehyde solutions I was hoping it wold work with acetaldehyde as well.


What's nice about doing it this way is that you lose no product during the testing.
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nux vomica
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[*] posted on 10-12-2015 at 18:08


I ran another batch last night and ended up with 60mls of acetaldehyde ethanol mix I will try your suggestion if I can tonight thanks nux.
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[*] posted on 9-3-2016 at 20:46


Huh I found a patent that said Acetaldehyde can be prepared by dry distilling/ pyrolyzing Barium Formate. Might be interestng to anyone looking for alternate routes to such a product.

EDIT: I'm reading old SM threads on the topic, and I can't get a consistent answer, some say the pyrolysis produces Acetone or Formaldehyde.


[Edited on 10-3-2016 by Daffodile]
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clearly_not_atara
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[*] posted on 23-3-2016 at 14:22


Both quotes from page 2:

Quote:
When you boil pyruvic acid with diluted H2SO4 you get acetaldehyde boiling out of the reaction.
Pyruvic acid is easily prepared from sodium pyruvate available over the net (unsuspicious not so expensive) or at the healthstore (expensive). Stochiometric amounts of HCl should do the trick I guess.


Quote:
the condensed chemical dictionary states that pyruvic acid is derivated by dehydration of tartaric acid by distilling with potassium acid sulfate so both decarboxilation and pinacol rearrangement happen in this reaction.


Both from page 2. I noticed that the mechanisms of these reactions are all acid-catalyzed, and in fact are all catalyzed by H2SO4. Tartrate undergoes a pinacol rearrangement to oxaloacetate, which decarboxylates to pyruvate, which decarboxylates to acetaldehyde. Why not simply heat tartaric acid in sulfuric acid?
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clearly_not_atara
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[*] posted on 28-3-2016 at 11:48


http://www.organic-chemistry.org/abstracts/lit3/684.shtm

Selective, aerobic, uses catalytic 4-hydroxy-TEMPO, ferric nitrate, sodium chloride, and silica. Would've edited this into my last post but I can't and this reaction looks frankly amazing from an atom economy and safety standpoint.

[Edited on 28-3-2016 by clearly_not_atara]
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nux vomica
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[*] posted on 12-9-2016 at 19:15


Link to youtube video https://youtu.be/7XNoWUeWxIk
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Magpie
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[*] posted on 12-9-2016 at 19:47


Nice going nux! Please give us the details on this preparation including purification and the yield.

I love seeing use of the peristaltic pump, and have noted your fine homemade mantle. ;)

Also, did you make those joint clips? I want some of those for high-temperature reactions. What kind of wire did you use? Anything special or just coat hanger wire?

[Edited on 13-9-2016 by Magpie]




The single most important condition for a successful synthesis is good mixing - Nicodem
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nux vomica
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[*] posted on 12-9-2016 at 20:19


Quote: Originally posted by Magpie  
Nice going nux! Please give us the details on this preparation including purification and the yield.

I love seeing use of the peristaltic pump, and have noted your fine homemade mantle. ;)

Also, did you make those joint clips? I want some of those for high-temperature reactions. What kind of wire did you use? Anything special or just coat hanger wire?

[Edited on 13-9-2016 by Magpie]


Thanks magpie i am going to do some more work on the purification tonight so i can post some more info .

I find i use the peristaltic pump more than a dropping funnel as long as the silicon tube can take the liquid flowing through it.

I got the clips off ebay after the plastic ones kept melting or cracking.

[Edited on 13-9-2016 by nux vomica]
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Magpie
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[*] posted on 13-9-2016 at 08:58


Quote: Originally posted by nux vomica  

I find i use the peristaltic pump more than a dropping funnel as long as the silicon tube can take the liquid flowing through it.


I replaced the silicone tubing with a smaller PVC (Tygon) tubing. It works just as well or better as the ID is smaller.

Quote: Originally posted by nux vomica  

I got the clips off ebay after the plastic ones kept melting or cracking.


I tried to make those out of coat hanger wire but it is too stiff.




The single most important condition for a successful synthesis is good mixing - Nicodem
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nux vomica
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[*] posted on 14-9-2016 at 19:10


Ive uploaded another video showing the purification of the acetaldehyde and the yield.
https://youtu.be/-x_lMokdjxk



20160913_182448.jpg - 793kB

20160913_191508.jpg - 643kB
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Magpie
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[*] posted on 14-9-2016 at 22:08


Very nice. I like the simplicity. Does the CaCl2 absorb water? Are azeotropes a concern? Did you have a lot of bumping?

I have tried that method for making butyraldehyde and propionaldehyde without much success(per Brewster). But CaCl2 was not used.

I will definitely be trying this.




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nux vomica
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[*] posted on 14-9-2016 at 22:39


Quote: Originally posted by Magpie  
Very nice. I like the simplicity. Does the CaCl2 absorb water? Are azeotropes a concern? Did you have a lot of bumping?

I have tried that method for making butyraldehyde and propionaldehyde without much success(per Brewster). But CaCl2 was not used.

I will definitely be trying this.


thanks magpie I got the information out of a book on google books


Capture 2.PNG - 42kB Capture.PNG - 45kB

The calcium absorbs the water and seem to smooth the boiling out.
As I understand it there isn't a azeotrope with water or ethanol so separation is reasonably straight forward.

Cheers nux.
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nux vomica
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[*] posted on 26-9-2016 at 23:53


I found a intresting occurrence happening in the storage bottle that my Acetaldehyde is kept in, there seems to be crystals of some sort forming on the walls of the bottle , i can only presume that metedehyde is forming and i wonder if a tiny amount of Sulfuric Acid has somehow contaminated the bottle and has catalysed some of the Acetaldehyde.

20160927_173827.jpg - 489kB
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clearly_not_atara
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[*] posted on 17-11-2016 at 13:40


Found this by accident, no really:

https://books.google.com/books?id=Cbc2AAAAQBAJ&pg=PT1830&lpg...

Quote:
Oxidation of alcohols with NaOCl can also be performed in the absence of nitrosyl radicals or a transition metal by the addition of certain promoters such as phase transfer catalysts, beta-cyclodextrin, or the use of an ionic liquid as solvent. The PTC/NaOCl protocol has emerged as the most convenient method of choice. A distinct advantage of the PTC/NaOCl protocol relative to the NaOCl/AcOH procedure is the ability to oxidize primary alcohols to aldehydes with minimal overoxidation to the ester, and the ability to oxidize alcohol substrates selectively in the presence of double bonds. In addition the PTC conditions do not require the use of chlorinated solvents and often afford fast rates of reaction at ambient temperature.


It appears that the likely mechanism of the hypochlorite/PTC oxidation is the electrophilic addition of the alcohol to hypochlorite ion:

RCH2OH + OCl- >> OH- + RCH2OCl (slow)

This is deprotonated by hydroxide, which is extremely basic in aprotic solvents:

RCH2OCl + OH- >> RCHOCl- + H2O (fast) [solvent cage effect]

and eliminates chloride:

RCHOCl- >> RCHO + Cl- (fast)

The aldehyde doesn't react further because this intermediate forms:

RCHO + OCl- >> RCH(OCl)O-

which is both much less acidic (negatively charged) and does not generate free hydroxide ion, so the elimination of HCl to form RCO2- is much less favorable.

Examples:

1-octanol + NaOCl [EtOAc/H2O, Bu4NBr] >> 1-octanal (86%)

15-desmethyl-cholesterol + NaOCl [EtOAc/H2O, Bu4NBr] >> 15-desmethyl-cholesterone (72%)

http://www.sciencedirect.com/science/article/pii/S0040403998...

Another version is catalyzed by cyclodextrin (Febreze) and occurs in water:

cinnamyl alcohol + NaOCl [beta-cyclodextrin, water] >> cinnamaldehyde (99%)

The cyclodextrin procedure may be more appropriate for ethanol, actually.

[Edited on 17-11-2016 by clearly_not_atara]
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