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Author: Subject: Acetaldehyde synthesis
Magpie
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[*] posted on 12-3-2017 at 10:22




I had a suspicion that this was not a practical route to acetaldehyde. Usually practical routes can be readily found in published procedures.

Quote: Originally posted by byko3y  

I have no double the reaction is possible, but I have no idea how to perform it. The only thing I'm sure is that you can't get acetaldehyde by heating ethylene glycol in a dillute sulfuric acid.


I take it that you have tried it, then?




The single most important condition for a successful synthesis is good mixing - Nicodem
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byko3y
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[*] posted on 12-3-2017 at 11:34


I did not try exactly this one, but did something similar. Such additional entrainer as water leads to complex reactions of acetaldehyde with itself and ethylene glycol.
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[*] posted on 18-3-2017 at 09:32


US2042224 Process of converting a polyhydric alcohol to a carbonyl compound (Acetaldehyde from Ethylene glycol by Sulfuric acid at 150-175 C)

US2335238 By Zinc Chloride at -210-220 C

[Edited on 18-3-2017 by Waffles SS]
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clearly_not_atara
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[*] posted on 21-3-2017 at 13:50


Interesting. It seems that dilute sulfuric acid tends to favor the aldehyde where concentrated sulfuric acid may have given dioxane. However the requirement for pressurized reaction is an issue. Dilute sulfuric acid will lose water rapidly at 175 ºC. However it appears that you do get acetaldehyde by heating ethylene glycol in dilute sulfuric acid at 175 C under pressure while constantly replenishing water, although that may not be what byok3y envisioned when he said that.

The zinc chloride route is a vapor-phase reaction. That's kind of sad.

[Edited on 21-3-2017 by clearly_not_atara]
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[*] posted on 23-4-2017 at 17:06


I've heard from weiming1998 that calcium hypochlorite and ethanol can be used as the high heat of the reaction distills the low boiling acetaldehyde without reacting further to make chloroform and calcium formate. Also according to nurdrage, acetylaldehyde does indeed form as a side product of dioxane synthesis but the yield is very low as dioxane is the preferred product
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[*] posted on 23-4-2017 at 17:08


Quote: Originally posted by byko3y  
I did not try exactly this one, but did something similar. Such additional entrainer as water leads to complex reactions of acetaldehyde with itself and ethylene glycol.
That forms 1 methyl dioxylene by condensation of ethanediol and ethanal with the removal of water
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[*] posted on 23-4-2017 at 18:04


I think you can drop ethanol into warm (I don't know how warm... maybe 70 C?) aqueous sulfuric acid / potassium dichromate and collect the distillate?

If that doesn't work (I don't know why it wouldn't), you can surely do an anhydrous oxidation of ethanol with chromyl chloride or PCC.

Oh, I just read that the OP doesn't have any sodium dichromate. That could make things tricky....

[Edited on 24-4-2017 by JJay]




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clearly_not_atara
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[*] posted on 25-4-2017 at 22:28


Also, OP's last post was 15 years ago...

I wonder if ethylsulfuric acid or ethylsulfate salts will react with DMSO similar to ethyl tosylate and benzyl iodide. High temperatures may be required.
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[*] posted on 25-4-2017 at 23:39


Quote: Originally posted by clearly_not_atara  
Also, OP's last post was 15 years ago...

I wonder if ethylsulfuric acid or ethylsulfate salts will react with DMSO similar to ethyl tosylate and benzyl iodide. High temperatures may be required.


I don't know, but I have about a pound of ethylsulfate salts just sitting around collecting dust, and I've been meaning to pick up some DMSO... how high might these temperatures be?




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[*] posted on 26-4-2017 at 14:21


From Advanced Organic Chemistry, Fieser & Fieser, (c) 1961:

12.6 - Tosylate method - Kornblum found (1959) that primary saturated alcohols are converted into aldehydes in 60-85% yield by oxidation of the tosylates with dimethyl sulfoxide (DMSO) in presence of sodium bicarbonate at 150C. Benzylic tosylates are oxidized smoothly at 100C. The required esters can be produced from the halides; for example, by reaction of n-octyl iodide dissolved in acetonitrile with silver tosylate.

150 C is good for alkyl tosylates, so I would start there with sodium ethyl sulfate. It appears that basic conditions are preferable. Apparently I had swapped octyl for benzyl in my memory.

Acetaldehyde can ignite starting at 185 C. As such it is probably not advisable to perform the reaction much higher than 170 C.

[Edited on 26-4-2017 by clearly_not_atara]
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[*] posted on 26-4-2017 at 15:24


Hmm... this is probably one for a fume hood....



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[*] posted on 27-4-2017 at 08:54


When i was younger i produced once 0,2 liter acetaldehyde just for fun and curiosity with Limpricht-Piria reduction from 1856
In this case stochiometric Ca-acetate + Ca formate fine grinded and mixed very intimatelly. Poured it In a suitable metal retort or hemebuilt container and heated it very slow (avoid the carbonisation) till slight red colour ( cca 500 degrees.) appeared. If no more liquid ceased the reaction was done.

Well known, that formate are poverful reducing agent. By heating need calculating with byside reaction f. e. chain cracking too. The prep is not optimal, but rough materials are cheap and easy to get. The simplified reaction:

(CH3COO)2Ca + (HCOO)2Ca ——> 2 CH3CHO + 2CaCO3

Methode also good for other aldehyde from Ca- carboxilic salt

yield was 30%, the purification was over ammonia-aldehyd. It is a possible way to get higher yield grinding of materials with ball mill, and really controlled slow heating. Good luck for follower
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[*] posted on 26-5-2017 at 13:29
Copper Oxide Catalyst for Ethanol Dehydrogenation


I think this is a good resource for this thread,

This paper outlines the preparation of copper oxide catalysts for the dehydrogenation of ethanol to acetaldehyde, and also gives data on each catalyst's activity over time and selectivity for acetaldehyde.

Some catalysts in this paper are claimed to produce high selectivities for acetaldehyde (~90%), and after 24hr runs, were easily regenerated to almost 100% of their original activity.

It's worth a look

Attachment: Dehydrogenation of Ethanol to Acetaldehyde.pdf (1.1MB)
This file has been downloaded 287 times

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clearly_not_atara
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[*] posted on 19-7-2017 at 13:49


This paper outlines the use of N-chlorosuccinimide for the selective oxidation of alkoxides:

https://www.researchgate.net/profile/Adam_Lee6/publication/2...

R-CH2OH + B- >> R-CH2O- + BH

R-CH2O- + ClSu >> R-CH2OCl + Su-

R-CH2OCl + B- >> R-CH(OCl)- + BH

R-CH(OCl)- >> R-CHO + Cl-

It appears that you could use this to oxidize sodium ethoxide using TCCA which IIRC dissolves in ethanol. Sodium ethoxide can be prepared "OTC" using excess anhydrous sodium hydroxide (it is necessary to wear a face shield when working with anhydrous sodium hydroxide):

http://www.sciencemadness.org/talk/viewthread.php?tid=2656

Excess TCCA will probably result in the formation of chlorinated acetaldehydes, though, and it might be preferable to use a chlorinating reagent of constant strength (TCCA's first, second, and third chlorines have different activation energy for release).

[Edited on 19-7-2017 by clearly_not_atara]
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[*] posted on 20-7-2017 at 06:59


It is known that alkoxides are prune to oxidation by a regular air. However, I don't seem to find any reactions of N-chlorosuccinimide with alkali alkoxides, but I think the only reaction is reversible formation of alkyl hypochlorite, which is known to decompose into aldehyde and/or ester.
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[*] posted on 25-7-2017 at 21:52


Has anyone had any success by oxidizing ethanol using hot potassium dichromate H2SO4 solution?
I have about 600g of potassium dichromate on hand and im planning of trying it this coming weekend.
The question i have is with dilution, and whether or not its necessary. In the following prep they use quite high dilutions and they also add the ethanol chromate mixture to the hot acid slowly.
https://erowid.org/archive/rhodium/chemistry/acetaldehyde.ht...
I would try this however i only have potassium dichromate on hand and thus i would have serious solubility issues, using an enormous dilution seems counter productive and im sure it would result in loss of yield due to ethanal solvating in the mixture and not distilling out and also limiting the batch size.

However i recently discovered the following video where this guy simply mixes the dichromate sulfuric acid and ethanol and then distills it, he doesn't dilute the ethanol at all and only uses a 1m solution of H2SO4.

If this video is anything to go by then the chances of over oxidation are actually quite slim provided the conditions are kept mild, then mixing the components without caring too much about limiting the dichromate available seems unnecessary.

I might just try doing this wile using a slight excess of ethanol. I was just wondering if others had experimented with this before i go ahead.

Edit: shit i forgot to reference the video.
https://www.youtube.com/watch?v=i7Ai5JdPYaY

[Edited on 26-7-2017 by Assured Fish]
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[*] posted on 25-7-2017 at 22:44


Overoxidation is almost certain to happen unless the acetaldehyde is removed as it forms. I don't think enormous dilution is necessary. I'm going to give this a try soon but plan to use sodium dichromate.

I think Tdep has made acetaldehyde with dichromates.




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[*] posted on 19-12-2017 at 20:43


Ok so i found a paper recently that claims its possible to oxidize primary and secondary alcohols using aqueous hydrogen peroxide with a catalytic amount of bismuth tribromide.

Courtesy of CJ: Attachment: lee2015.pdf (143kB)
This file has been downloaded 88 times

I think this could work rather well for the prep of acetaldehyde.
A fractional distillaion set up could be employed and the boiling flask charged with the aqueous H2O2 and ethanol and 10mol% of BiBr3.
The Boiling flask temp would have to be monitored but once 70*C is reached and the contents of the flask begin refluxing, then the acetaldehyde should be more than volatile enough to make its way past the fractionating column while the ethanol should remain mostly in the boiling flask provided the temp is controlled.

The distillate could then be reacted with ammonium hydroxide and filtered to acquire the ammonium acetaldehyde trimer.

I thought about this being done with just standard refluxing however the paper suggests that its still possible for over oxidation to take place if the reflux is continued for too long.

The paper seems to indicate that the reaction proceeds via the in situ generation of HBrO.

As for the BiBr3, from what ive read it can be conveniently prepared by the direct oxidation of bismuth with elemental bromine or by the reaction of hydrobromic acid with bismuth trioxide.

The only issue i see with BiBr3 is that according to the wiki the NFPA 704 code for health hazard is a 4. This seems rather odd as the same code is a 2 for the triiodide and trichloride.
I realize that NFPA 704 is not really a good indicator for toxicity and it can be rather inacurate at times but this still seems rather odd for a substance that is only corrosive.
Granted according to what ive read its very corrosive.
Probably safe to handle such a compound in a fume hood or with a respirator to be on the safe side.

https://en.wikipedia.org/wiki/Bismuth_tribromide
https://en.wikipedia.org/wiki/Bismuth_chloride
https://en.wikipedia.org/wiki/Bismuth(III)_iodide

http://www.nilechemicals.com/BISMUTH%20BROMIDEMSDSLAB.htm
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