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Magpie
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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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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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Waffles SS
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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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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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The jersey rebel
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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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The jersey rebel
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| 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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JJay
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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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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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JJay
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| 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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clearly_not_atara
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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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JJay
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Hmm... this is probably one for a fume hood....
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Aqua-regia
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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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boilingstone
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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 2051 times
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clearly_not_atara
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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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byko3y
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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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Assured Fish
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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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JJay
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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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Assured Fish
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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 998 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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Xrpdguy
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Did anyone try to oxidase alcohol by using conc. Hydrogen-peroxide and Cu2+ salt as a catalyst like basic copper carbonate (malachite)?
I did.
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Assured Fish
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| Quote: |
Did anyone try to oxidase alcohol by using conc. Hydrogen-peroxide and Cu2+ salt as a catalyst like basic copper carbonate (malachite)? I did.
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What was your result and precisely how did you do it?
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Xrpdguy
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| Quote: Originally posted by Assured Fish |
| Quote: |
Did anyone try to oxidase alcohol by using conc. Hydrogen-peroxide and Cu2+ salt as a catalyst like basic copper carbonate (malachite)? I did.
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What was your result and precisely how did you do it? |
Actually that was one of my project where I determined the kinetic of that reaction. You can simply use one vial of 5 ml and add 1 ml of ethanol and
0.5ml of 30% hydrogen peroxide and few drops of concentrated solution of copper sulfate, copper chloride or copper chloride-trihydrate. Also you need
to heat the mixture for about and minute or more and you can play with various temperatures from 50 to 200 degrees of Celsius.
I noticed that around 300 degrees Celsius the reaction became so fast and vigorous and the vial explode.
Be careful because of concentrated hydrogen peroxide. It can explode on lower temperature. As he said you can use instead of solution of copper salts
malachite as a catalyst.
At the end of the reaction the main product is ethanol and I determined that by smell.
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Assured Fish
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Interesting, i suspect you mean to say "at the end of the reaction the main product is acetaldehyde"
Which you determined by smell.
I suppose its worth investigation, though i think we have all managed to make a small amount of acetaldehyde, its just very difficult to make a usable
quantity.
I managed to isolate about a quarter tea spoon full of the aldehyde ammonium trimer, though the major product of the oxidation (potassium dichromate
as oxidizer) was definitely acetic acid.
Its not easy to tell the difference between both the acid and the aldehyde by smell from what i gathered as both smells tend to mix together and
somewhat trick the senses.
I haven't yet gotten the chance to smell pure acetaldehyde as its always got small amounts of acetic acid mixed into it.
Im not gonna say you didn't make acetaldehyde but im just skeptical that it was the major product, especially given your means of analysis.
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Xrpdguy
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| Quote: Originally posted by Assured Fish | Interesting, i suspect you mean to say "at the end of the reaction the main product is acetaldehyde"
Which you determined by smell.
Im not gonna say you didn't make acetaldehyde but im just skeptical that it was the major product, especially given your means of analysis.
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I am made a mistake in typing sorry about that, you're right I wanted to say acetaldehyde instead of ethanol.
But acetaldehyde has a fruity odor and I determined only by smell and didnt notice an odor of anything other( like the rest of ethanol).
I agree that I need to do some other analyses but my project is still in a 'pilot step'.
There are many reactions for the termination of aldehydes like Tolen's test.
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draculic acid69
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In regards to the h2so4 and ethylene glycol method one should probably just follow the dioxane method and attach a hose to the vacuum takeoff and
bubble the what should be gaseous acetyldehyde through some nh3 to collect it as the adduct and work it up from there.dioxane is certainly the main
rxn product of that rxn and ethanal is just a small side product.maybe nh3 could be placed in the receiver to catch it as it comes over from the rxn
pot as the adduct.nh3 won't react with dioxane will it? Maybe it will stop the rxn of ethanal,water and glycol as it will be neutralized quickly and
not have time to react.
[Edited on 27-3-2019 by draculic acid69]
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draculic acid69
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Calcium formate and calcium acetate destructively distilled seems to be the best easiest way to go if you need some for a rxn.can easily be scaled up
to create larger amounts quickly.
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