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Author: Subject: Acetaldehyde synthesis
JohnWW
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[*] posted on 26-2-2008 at 13:19


Yes, pentaerythritol, C(CH2OH)4, is made by the reaction of CH3CHO and CH2O in the presence of a strong alkali like KOH. The stuff is used for the manufacture of powerful nitro-explosives, especially the tetranitrate ester.

[Edited on 27-2-08 by JohnWW]
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PHILOU Zrealone
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[*] posted on 27-2-2008 at 03:34


Quote:
Originally posted by carbonic
but really, what is acetaldehyde good for?


Reactive molecule to introduce CH3-CHOH- or CH3-CH= moiety into a bunch of molecules displaying affinity for the carbonyl part.

[Edited on 27-2-2008 by PHILOU Zrealone]




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[*] posted on 11-3-2008 at 17:04


Quote:
Originally posted by solo
Note : here is a recent posting on the subject at the Hive,.......".Novel Discussions"

slothrop
(Newbee)
12-17-02 10:58
No 390260
Benzyl alcohols to Benzaldehydes

From Synlett 2002, 12, pp2041-42,
A Novel and Efficient Oxidation of Benzyl Alcohols to Benzaldehydes with DMSO Catalyzed by Acids
Typical procedure: A mixture of 557 mg of benzyl alcohol, 0.15 mL of HBr (48 %) and 5 mL of DMSO was stirred in an oil bath at 100°C. TLC (petroleum ether/diethyl ether, 1:1) was used to indicate the completion of the reaction (3 h). To the reaction mixture were added 5 mL brine followed by extraction with 30 mL of diethyl ether. The ether layer was washed with brine (5 mL x 4). Evaporation of the ether and subsequent buld to buld distillation produced 530 mg of benzaldehyde in 95 % yield.
//Tyrone Slothrop



How does it work?
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MagicJigPipe
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[*] posted on 11-3-2008 at 17:20


This sounds almost too good to be true. Has anyone even heard of this before? Or tried it?

I suppose I'll try it tomorrow since I have all of those reagents.




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PHILOU Zrealone
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[*] posted on 12-3-2008 at 02:26


Quote:
Originally posted by MagicJigPipe
This sounds almost too good to be true. Has anyone even heard of this before? Or tried it?

I suppose I'll try it tomorrow since I have all of those reagents.


CH3-SO2-CH3 is maybe a mild enough oxydiser...I suspect it must turn into CH3-SO-CH3 and maybe into CH3-S-CH3...but then you will notice by the very distinctive smell of it :D:cool:




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[*] posted on 12-3-2008 at 03:39


It is some kind of a variation on the Swern oxidation, but it can only work on benzyl alcohols. Alcohols having alpha-hydrogens succumb to side reaction under such harsh conditions. Instead they require acid scavengers and acid chlorides or anhydrides for the DMSO activation under <0°C temperatures.

PS: DMSO is not Me-SO2-Me, it is Me-SO-Me and after reduction with benzyl alcohol (or whatever else) it converts to dimethyl sulfide (Me2S).
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[*] posted on 28-4-2008 at 18:30


In the dictonary of applied chemistry on google books, p103 second column the dichromate + sulfuric oxidation is mentioned, but also another another I thought was good.

Manganese dioxide - aka the black packed substance in an alkaline battery. If you cut open the bottom of a big battery like a D cell, you can scoop out the zinc powder anode and save it. Watch out, it is caustic (er, alkaline).

Then, bend the case a bit to crack apart the 50+g of MnO2. I put a few g of this MnO2 plus a g or so of bisulfate beads into a jar and added everclear. Not much happening instantaneously, but when left overnight I saw a "dew" of droplets had appeared at the top of the walls. Opening and smelling, it was undoubtedly the light, clear fruity scent of acetaldehyde.

I suppose that conc. H2SO4 is better suited for this than the weaker bisulfate salt, but at least it proves that the cheap and readily available MnO2 can oxidize a primary alcohol to an aldehyde.
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[*] posted on 29-4-2008 at 16:44


Quote:
Originally posted by detritus
In the dictonary of applied chemistry on google books, p103 second column the dichromate + sulfuric oxidation is mentioned, but also another another I thought was good.

Manganese dioxide - aka the black packed substance in an alkaline battery. If you cut open the bottom of a big battery like a D cell, you can scoop out the zinc powder anode and save it. Watch out, it is caustic (er, alkaline).

Then, bend the case a bit to crack apart the 50+g of MnO2. I put a few g of this MnO2 plus a g or so of bisulfate beads into a jar and added everclear. Not much happening instantaneously, but when left overnight I saw a "dew" of droplets had appeared at the top of the walls. Opening and smelling, it was undoubtedly the light, clear fruity scent of acetaldehyde.

I suppose that conc. H2SO4 is better suited for this than the weaker bisulfate salt, but at least it proves that the cheap and readily available MnO2 can oxidize a primary alcohol to an aldehyde.


That MnO2 is also mixed in with carbon, so be careful using that in any experiments, e.g. as a catalyst in the thermal decompsition of KClO3 to generate oxygen gas.
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[*] posted on 30-4-2008 at 15:28


good point. do you happen to know the approxamate ratios used in alkaline cells? Carbon to MnO2, that is...
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[*] posted on 2-5-2008 at 01:07


Quote:
Originally posted by detritus
good point. do you happen to know the approxamate ratios used in alkaline cells? Carbon to MnO2, that is...


I'm not sure exactly. I think there might be a patented formulation for the certain battery types. Will have to look into it more later.

Extraction of the pure compound would be some hard work. Some ideas of extraction: Any water solubles like the chloride could be removed by heating the solid with water and strong stirring. The carbon is insoluble in water but so is MnO2, though MnO2 will dissolve in HCl (Caution: chlorine gas): MnO2 + 4 HCl -> Cl2 + MnCl2 (pink) + 2 H2O. The carbon should be insoluble. Should be able to get MnCO3 (insoluble) from MnCl2 and Na2CO3 solutions. Then heat MnCO3 to 260°C (in air), and react the residue with very dilute cold HCl acid to get MnO2. It is also said to form by precipitating from MnCl2 with an alkaline hypochlorite solution, etc.

[Edited on 2-5-2008 by Schockwave]
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[*] posted on 9-7-2009 at 10:48


Sorry for bringing up an old tread.

I once made peroxi-acetone in my old kewl days. I didn't read forums like this at that time, so I thought that the warmer the solution the more peroxi-acetone will form;), so I mixed acetone with hydrogen peroxide, I can't remember the ratios (I also didn't care too much with it:)) but I seem to remember that the acetone were in large excess.

I dumped the HCl into the mix by mililiters until it got warmed then put it into my cellar, after a couple of days filtered off the product...

The interesting point is... when i took the remained most-wit-buddha-knows-what-in-there solution, heated up a copper wire and put in it and it started to foam and heat immeadiately, I never had acetaldehyde only did tube experiments with hot penny, but the smell was the same IIRC, the whole solution (about 300ml) were boiled out of the jar, a lot of gas were generated!

Does somebody has a guess what could that be?

Any answer or guesswork would be appreaciated. Thanks!
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[*] posted on 2-9-2009 at 14:59


Seeing as the thread is "alive" again I'll add something.

@Nicodem: This is the Kornblum oxidation. The HBr is there to form the alkyl bromide, which is attacked Sn2 style to form the same activated complex as all the other related DMSO oxidations (pfitzner moffatt, swern, onodera-albright, albright-goldman etc etc.) The reaction is NOT limited to benzyl alcohols. The original work was done with alpha-haloketones to yeild glyoxals, but some modifications were introduced to make it work better for other substrates. In fact the benzyl halides reacted to give poor yields of benzaldehyde. Generally the conditions consist of an alkyl halide, NaHCO3 as a base, and DMSO as solvent, temperature ca. 140C. If X= Cl or Br, then 1.5eq. NaI can be added to facilitate reaction. The reaction generally works better with the corresponding tosylates (X= OTs) and this will work with primary substrates to give the corresponding aldehyde. The tosylate can be prepared as "normal" using TsCl on the appropriate alcohol, or by using silver tosylate (TsOAg) on the corresponding halide. The tosylate is then reacted with DMSO, and the conditions are somewhat milder if I remember correctly; Stirring the tosylate in DMSO at room temperature is sometimes satisfactory.
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[*] posted on 3-9-2009 at 11:39


I made acetaldehyde by refluxing 93% ethanol on hot copper, after 4 hour of refluxing the acetaldehyde started to distill over the column... I think it was heavily contaminated but sniffing it behaved the same way as formaline.
Theres nothing in the first couple of seconds then you cry like hell...

I also pured a small amount of destillate (I do not know what was the contaminant but the boiling point of the distillate was much higher than 20°C) into saturated NH3 solution and it warmed a lot and gave a white emulsion (I think it would have been impossible to filter) anyway my three necked flask broken at the 5th hour. So I shut down the setup... When I went back to check the setup the whole thing burned... scared the shit out of me to put it soft...

I ordered another flask for my home-made acetaldehyde plant and I will give this another try when I have the time and post the results.

By the way I can post picture of the whole setup taken before it fell apart if anyone is interested.
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[*] posted on 3-9-2009 at 12:01


Can NaHSO4 be substituted for KHSO4 in the dehydration of tartaric acid to pyvuric acid?
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Klute
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[*] posted on 3-9-2009 at 14:04


Please, do post theses pictures!



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[*] posted on 5-9-2009 at 08:15
Pictures from the setup


The first picture is talking to itself... the tube were filled with copper foil peeled off from gauging rods ;)

The second is destined to illustrate the small tube in the three necked RB flask. It is necessary for the continuous reflux of ethanol.

The setup is on the third picture...

The condensation front in the condenser was kept at the level of the second bubble IIRC.

I inserted two scrubbers opposed to each other to the end of the plastic tube so as to the starting point of the oxidation would be indicated, when the reaction started I sampled the generated gas once in a while in a test tube, smelled and lit it... it seemed to mainly consist of hydrogen because it was odourless and burned with a blue flame in dark.

I am gona buy a controller for the next run too to keep the reactor temperature below 300°C.

I saved the milk like product, which I think mainly consists of aldehydeammonia... I do not know what to do with it in this form... any idea?

picture 01.JPG - 14kB picture 03.JPG - 35kB

picture 02.JPG - 57kB
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Klute
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[*] posted on 5-9-2009 at 17:32


Beautifull setup! Unfortunate that the experiment wasn't very conclusive.. Please let us know of futur tries!



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[*] posted on 11-10-2009 at 04:38


Ok... everithing gone to waste what I wrote abot half an hour, this is definitely not my day.

So, I gradually increased the setpoint of the glass reactor from 280°C to 420°C.

From two liter ethanol after a couple of hours of run, I fractionated about 50ml foul smelling liquid T=20-60°C wich gave cristallyne solid on addition of NaHSO3.

I am gona try again with copper foil.

setup2.JPG - 39kB

Because... I used stripped copper cord stuffed in the glass tube at this experiment.

[Edited on 11-10-2009 by Jimmymajesty]
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[*] posted on 13-10-2009 at 01:36


Could you make acetaldehyde from chloral hydrate?
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[*] posted on 13-10-2009 at 05:48


Not likely, unless you want to spend a long time/expensive reagents removing them chlorine atoms...
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[*] posted on 23-11-2009 at 11:32


Reply Post: 2312 ethylene glycol - again

Has anybody acces to this paper:
Tetrahedron Volume 58, Issue 11, 11 March 2002, Pages 2091-2094 Ethylene glycol to acetaldehyde-dehydration or a concerted mechanism
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[*] posted on 23-11-2009 at 11:44


Since this is not the place for it you may have better luck in the Reference request thread then you will here.




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[*] posted on 7-12-2009 at 18:51


Looking back through this thread, I see that ethylene glycol has been discussed in the context of sulfuric acid oxidation, but not otherwise (and it looks like dioxane is actually what you'll get...).
However, after seeing this: www.sciencemadness.org/talk/files.php?pid=75149&aid=1734 elsewhere here, I wonder about hypochlorite as a way of oxidizing ethylene glycol to acetaldehyde.

In this case, it looks like the primary products are formaldehyde, acetaldehyde and ethylene. But they're discussing an uncontrolled oxidation with concentrated oxidizer. It seems like slow addition of hypochlorite solution to hot ethylene glycol, with condensation of any evolved gas, might result in a greater proportion of acetaldehyde.

I'll try this and report on the results.

So far as dioxane (or the possibility of other products) is concerned, it seems like the production of such a compound might be heavily influenced by the amount of water present in the system. It looks like condensation to dioxane would be driven by the water-withdrawing nature of H2SO4, so that some difference in conditions (like more water in the system) might instead allow the H2SO4 to act as oxidizer, and result in different products.
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[*] posted on 7-12-2009 at 22:23


First, they are referring to polyethyleneglycol, H(-OCH2CH2O-)nH, not ethylene glycol.

Second, this is not a simple oxidation, the paper explicitly mentions radical mechanisms, look on page #5 of the PDF. I suggest that you might show how oxidation of HOCH2CH2OH (C2H6O2) leads to CH3CHO (C2H4O)

Third, attempting to keep it controlled looks as if doing so may be difficult; there are plenty of easier and higher yielding ways.


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[*] posted on 8-12-2009 at 02:07


Bbartlog, ethylene glycol and acetaldehyde are in the same oxidation state. Therefore, you can not obtain acetaldehyde from ethylene glycol oxidation. I suggest you to learn how to count oxidation states as this is pretty much basic chemistry without which you can not do.

You can not just rearrange ethylene glycol or 1,4-dioxane to acetaldehyde using protic acids because primary alcohols do not undergo eliminations that easily, while the conditions required would be too harsh for the acetaldehyde to "survive". It might be possible by passing ethylene glycol or 1,4-dioxane vapors over some some solid acid (alumina, acidic zeolites, silica, etc.) at high temperature (300°C or more). Such heterogenous conditions should prevent the acetaldehyde to decompose, but still yielding a mixture of products. But this is not easily done in an amateur setting and besides I was not able to find any references confirming such an idea would work.




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